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1
Wu, Juliana S. B. Massachusetts Institute of Technology. "Characterizing the dam break release." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/92213.
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Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references (page 41).
The failure of a dam can cause disastrous consequences, thus understanding the nature of a dam break is of utmost importance. A model of a dam break was built and used to profile the resulting wave. The gate release was characterized to check for consistency, maximum velocity, and it's profile. Matlab code was created to analyze both the gate speed and the wave velocity. The maximum velocity was 1503.2 cm/s and there a 30% deviation at most.The wave velocity was found to increase as the water reservoir height was increased. An equation was derived that had a 0.96 correlation coefficient thus proving that the relationship between velocity and reservoir height was accurate. Further research can be done using a cantilevered plate downstream of the dam break to analyze the forces generated.
by Juliana Wu.
S.B.
2
MODOLO, A. V. F. "ESCOAMENTO de Materiais Viscoplásticos: Dam Break Flow." Universidade Federal do Espírito Santo, 2017. http://repositorio.ufes.br/handle/10/9757.
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Previous issue date: 2017-03-24Ao longo do último século, o Dam Break Flow vem sendo estudado por muitos autores. A compreensão deste tipo de fenômeno é de grande relevância, uma vez que envolve aplicações em barragens que oferecem múltiplos benefícios para a humanidade. Porém, o rompimento de uma dessas barragens pode trazer consequências indesejáveis e imensuráveis para a sociedade e para o setor de mineração, por exemplo. Neste trabalho estamos interessados em entender como o número de Froude e as propriedades não-newtonianas, particularmente a viscoplasticidade, afetam o perfil de interface do escoamento e a distância alcançada pelo material após o Dam Break Flow. Tais resultados são comparados com o deslocamento de um fluido newtoniano. Através de uma simples abordagem experimental, uma solução de material viscoplástico ou newtoniana incialmente armazenada em um reservatório é instantaneamente liberada. As imagens do escoamento são capturadas durante o teste de duas maneiras diferentes. Uma é feita utilizando uma câmera CCD e a outra é através da Velocimetria por Imagem de Partícula. A partir das imagens obtidas pela câmera CCD, obtém-se um mapa do escoamento, com as suas respectivas velocidades, nível de líquido, formato das interfaces ar-líquido e distância percorrida pelo material são observadas. Já os resultados obtidos com o PIV, são para determinar o campo de velocidade dos momentos iniciais do Dam Break Flow para os diferentes tipos de materiais estudados. Neste trabalho, é mostrado que a plasticidade do material tem total influência sobre a distância alcançada pelo escoamento e também resultam em instabilidades ao longo do mesmo. Foi ainda identificado que o fluido viscoplástico alcança velocidades iniciais maiores que o caso newtoniano. Porém, no decorrer do escoamento, decrescem rapidamente. Quando analisado o caso viscoplástico para um leito com rugosidade, nota-se que para uma superfície lisa, há deslizamento do material de forma significativa para altos valores de plasticidade. Através da análise com PIV, foi constatado que a velocidade de frente de onda é um pouco menor do que a velocidade máxima obtida pelo escoamento. Palavras chave: Dam Break Flow, material viscoplástico, PIV, plasticidade, deslizamento.
3
Tang, Gaven. "Two-dimensional mobile-bed dam-break model." Thesis, University of British Columbia, 2012. http://hdl.handle.net/2429/43508.
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Sudden and catastrophic dam-breaks typically induce high bed shear stresses downstream as the flood-wave propagates over the alluvial channel and flood plain. In fact, the non-dimensionalized shear stresses are often high enough that they are comparable to those typically seen in the transport of sand. Despite the existence of these shear stresses, industry typically ignores sediment transport altogether and assumes a fixed-bed when modelling dam-breaks. This thesis will examine the validity of the fixed-bed assumption and create a depth-averaged 2D mobile-bed dam-break model. This model will then be tested by simulating the Malpasset (France) dam-break of 1959, and a sensitivity analysis will then be performed on the parameters of grain roughness, vegetation roughness, friction angle, grain size, and depth to bedrock to examine differences in inundation and flood-wave propagation.
4
Gozali, Salahudin. "Dam-break solutions for a partial breach." Thesis, University of Canterbury. Civil Engineering, 1991. http://hdl.handle.net/10092/7199.
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Four different numerical models are developed to simulate the flow resulting from a breached dam. The models are a level-reservoir-approximation model, an explicit method-of-characteristics model, an implicit method-of-characteristics model and a linearized implicit finite-difference model. The first model is based upon the storage form of the continuity equation, and the other models are based upon the complete St. Venant equations.
Laboratory experiments are performed to investigate the flow characteristics and to verify the validity of the numerical models. Comparisons between model results and experiment are used to evaluate the accuracy of the numerical models. These comparisons show that the explicit method-of-characteristics model always gives a more accurate solution than the other models. Computational problems, computer requirements and model robustness are also evaluated to assess ease-of-use of the models.
Finally, the experimental and numerical results were used to construct a simplified numerical model to compute dam-break outflow hydrographs. The outflow hydrographs computed by this simplified model agree relatively closely with the corresponding results computed by the explicit method-of-characteristics model for any breach size. This suggests that the simplified model can be used for a wide range of breach sizes and gives a maximum practical level of accuracy.
5
Chegini, Amir H. Nezamivand. "Investigation and analysis of dam-break flow problem." Thesis, University of Manchester, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.521520.
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Variations of the flow characteristicsh ave been investigatedf or the flow propagationd ue to a dam-plate removal. Experiments were carried out for various water depth ratios (Hj/H,, 0,0.1,0.45,0.7) in a flume with / without an obstacle downstream of the damsite. Measurementso f flow characteristicsw ere made in the laboratory using a Particle ImageV elocimetry (PIV) system.T o assessth e accuracyo f the PIV measuremenst ystem, Water Level Meter (WLM) measurements have been taken. Comparison of PIV and WLM measureds urfacee levationsa re presentedT. he image analysiss ystemv isualisedt he jet and mushroom formations as complex flow in the downstream section for the low depth ratios. The video image also illustrated the oscillation flow in the downstream channel for the high depth ratios. One-dimensional analytical and numerical calculations have been presented to simulate the experimental results. The numerical models use a semi-implicit Lagrangian finite difference scheme and a WAF Riemann problem based method, the governing equations being the Saint-Venant equations for an invisid and incompressible free surface flow. The models have the advantage that water motions can be simulated, and give particularly good results for the subcritical flow. In general, the models produced good agreement with experimental results.
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Lismanis, Brandon. "Numerical Modelling of Dam Breaching." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/24004.
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Until recently, research has been scarce in the field of physical modelling of dam breaching. Over the past few years, teams from the University of Ottawa, Canada, Delft University of Technology, Netherlands, and HR Wallingford, United Kingdom have worked on several physical models to help determine how various dam breaching characteristics vary due to changes in dam geometry and geotechnical properties. The purpose of this project is to use these new experimental data sets to compare and validate the applicability range of two existing pieces of software, MIKE11-DB and BREACH developed by the Danish Hydraulic Institute and National Weather Service, respectively. Several breaching characteristics such as the outflow hydrograph, peak flow, lag time, breaching time, breach width, and water level are considered in the present study. A sensitivity analysis is also performed on the model’s main input parameters and their sensitivity and performance is ranked accordingly.
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Natale, Elisabetta. "Dam break risk assessment in Baker Valley (Chilean Patagonia)." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/53069.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2009.Includes bibliographical references (leaves 57-59).
An hydroelectric project was proposed by HidroAysen Company in the Aysen Region of Chilean Patagonia. It consisted of the installation of five hydroelectric power stations, two on Rio Baker and three on Rio Pascua, with an average annual energy production of 18,430 GWH. The Environmental Impact Assessment (EIA) presented by HidroAysen lacked of a dam failure impact assessment, crucial to prevent or minimize the impact of unexpected flooding caused by a dam failure. A dam break risk assessment was performed for the so called Baker 2, a proposed concrete gravitational dam located on the Rio Baker, upstream the small community of Caleta Tortel, an area of concern for potential flooding. Using ORSA Code, software developed by a research collaboration between the University of Pavia and the University of Rome - La Sapienza (Italy), a computational model was performed to simulate the flood wave propagation associated with a dam break failure scenario. The areas subject to flooding were mapped on the digital elevation model (DEM) of the surface topography.
by Elisabetta Natale.
M.Eng.
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Pereira, Clicia Giovane Alves. "Estudo matemático do método SPH para modelo Wet-Dam-Break /." Presidente Prudente, 2019. http://hdl.handle.net/11449/181857.
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Orientador: Carlos Alberto Dutra Fraga FilhoBanca: Messias Meneguette Júnior
Banca: Vanessa Avansini Botta Pirani
Banca: Andriana Susana Lopes de Oliveira Campanharo
Resumo: Neste trabalho, apresenta-se o método Lagrangiano de partículas livre de malhas, Smoothed Particle Hydrodynamics (SPH). Neste método, o domínio do problema é discretizado empregando partículas que possuem propriedades físicas calculadas a partir das propriedades das partículas vizinhas, por meio de uma interpolação, utilizando uma função de suavização. O método foi aplicado para discretizar e adaptar para SPH um modelo de ruptura de barragem sobre um leito úmido conhecido como Dam-Break in Wet-Bed. Tal modelo, considerado ideal, é empregado nos testes de desempenho, precisão e confiabilidade de modelos matemáticos para validação de métodos numéricos aplicados a problemas de vertedouros em barragens hidrelétricas e ondas em praias.
Abstract: In this work, we present the Lagrangian mesh-free method of particles, Smoothed Particle Hydrodynamics (SPH). In this method, the problem domain is discretized using particles having physical properties calculated from neighboring particles by means of interpolation using a smoothing function. The method was applied to discretize and to adapt the SPH for a model of dam rupture on a wet-bed known as Wet-Dam-Break. This model, considered as ideal, is used in tests of performance, accuracy and reliability of mathematical models for validation of numerical methods applied to spillways problems in hydroelectric dams and waves at beaches.
Mestre
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Karakaya, Koray. "Numerical Simulation Of The Kirazlikopru Dam Failure On The Gokirmak River." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606039/index.pdf.
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Numerical dam break analyses of Kirazliköprü
Dam are performed under various hydraulic scenarios. Kirazlikö
prü
Dam is located on the Gö
kirmak River near the city of Bartin. The objective of these analyses is to investigate adverse effects of such dam break failure on the regions downstream of the dam. The numerical model used in the simulations is FLDWAV, which is developed by the National Weather Service (NWS) in the United States. It appears that most adversely effected regions are those that are closest to the dam location. The results of these simulations can be used sufficiently to prepare emergency action plans in case of possible failures.
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Aboelata, Maged A. "Conceptualization and Development of a Dam Break Life-Loss Estimation Model." DigitalCommons@USU, 2005. https://digitalcommons.usu.edu/etd/4540.
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Catastrophic events such as dam failures or severe floods are considered to be of low probability, although their consequences can be extremely high and might include loss of life. Earlier studies have linked circumstances surrounding historical darn failure events to actual loss of life and produced formulations using statistical analysis of these events. Shortcomings of these methods include the inability to adjust life-loss estimates based on the type of darn failure, global averaging of population at risk, and ignoring the dynamics of the evacuation process.
The main objective of this research is to develop a practical and improved life-loss estimation approach for use in dam safety risk assessment and emergency planning. The methodology is specifically formulated to overcome the limitations of previous. purely empirical, approaches. The approach takes into account the spatial and temporal distribution of flood water depth and velocity, fate of buildings, simulation of warning diffusion, and tracking the movement of people from their original location towards safe shelters.
The model created, called LlFESim, is designed to serve multiple function s. First, it can be used in a Deterministic Mode using best estimate inputs to obtain point estimates, or to test different policies for evacuation as well as different times of the day and for different dam breach flooding scenarios. Second, the Uncertainty Mode represents input and parameter uncertainties to provide estimates of life loss, and other variables relating to warning and evacuation effectiveness, as probability distributions. These distributions of life loss can be combined with estimates of the uncertainties in other risk assessment inputs, to obtain estimates of uncertainties in risk assessment results, including evaluations against tolerable risk guidelines.
Two communities were used to demonstrate the model performance. Deterministic Mode results display the various possible model outputs. Sensitivity analysis for the Deterministic Mode shows that the effect of warning issuance time is the dominant factor in the estimated life loss. However, other factors play an important role such as the time of day, effectiveness of the warning system, and shelter location. Uncertainty Mode results demonstrate the effect of uncertainties in model parameters and inputs on the model results.
11
Zagonjolli, Migena. "Dam break modelling, risk assessment and uncertainty analysis for flood mitigation /." London : Taylor & Francis, 2007. http://opac.nebis.ch/cgi-bin/showAbstract.pl?u20=9780415455947.
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Bornschein, Antje, and Reinhard Pohl. "Dam break during the flood in Saxony/Germany in August 2002." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-160588.
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The heavy rainfall event in August 2002 in Saxony/Germany caused the break of a flood retaining basin in a valley of the Erzgebirge Mountains. The rainfall event with ists hyrologic characteristics and dam break event were analysed and an outflow hydrograph was determing. The propagation of the dam break flood wave in the valleyas of the Briesnitz and Müglitz Rivers has been simulated. Calculated values were compared with some observed data.
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Bornschein, Antje, and Reinhard Pohl. "Dam break during the flood in Saxony/Germany in August 2002." Technische Universität Dresden, 2003. https://tud.qucosa.de/id/qucosa%3A28528.
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The heavy rainfall event in August 2002 in Saxony/Germany caused the break of a flood retaining basin in a valley of the Erzgebirge Mountains. The rainfall event with ists hyrologic characteristics and dam break event were analysed and an outflow hydrograph was determing. The propagation of the dam break flood wave in the valleyas of the Briesnitz and Müglitz Rivers has been simulated. Calculated values were compared with some observed data.
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Matson, Gary Paul. "Low Reynolds number, gravity currents : Newtonian exchange and viscoplastic dam break flows." Thesis, University of Bristol, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.437303.
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Jian, Wei. "Smoothed particle hydrodynamics modelling of dam-break flows and wave structure interactions." Thesis, University of Cambridge, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648472.
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McMullin, Nicholas. "Numerical and experimental modelling of dam break interaction with a sediment bed." Thesis, University of Nottingham, 2015. http://eprints.nottingham.ac.uk/29138/.
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A dam break event is considered, taking place over a uniform sediment bed. Understanding and modelling the erosion that occurs when the fluid behind the dam collapses at release has important applications in coastline morphodynamics / beach erosion modelling. A new coupled two dimensional Navier-Stokes solver and sediment transport model is presented with novel methods for dealing with non-converging solutions to the Navier-Stokes equations and a new adaptation to the Youngs [1982] volume-of-fluid reconstruction scheme. The implementation of a sediment transport model includes a new method for accounting for mass conservation for the transition of sediment between bed and flow as well as a novel method for accounting for the redistribution of material associated with the maintenance of the critical angle of repose or slope limit. The model is validated and then applied to a dam break simulation for various backwater and tailwater conditions. Classical experimental realizations of dam break events have involved the rapid removal of a barrier in a flume [e.g. [Levin, 1952; Dressler, 1954; Bell et al., 1992])]. However, early-time flow analysis encounters two problems with this method. Firstly, the removal of the barrier creates a strong vortex sheet on the face of the static fluid immediately behind the barrier that is not present in either the idealized problem, or the motivating environmental problems. Secondly, the removal of the barrier cannot take place instantaneously and so a brief jet-like flow is initially induced through the opening between the base of the barrier and the sediment layer. We partially circumvent these difficulties with the classical experiments by implementing a novel dam break barrier release, using a barrier similar to the wrapped-fabric design of [Dalziel, 1993], which minimizes the initial vortical disturbance. Three-dimensional stereoscopic Particle Image Velocimetry (PIV) measurements allow us not only to capture the velocity field in the laser-plane, but also perpendicular to it. These planar experimental results are compared to the results of the numerical study and the comparison is shown to be good while the simulation successfully converges.
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Al-Salihi, Adnan H. "Numerical and physical modelling of dam-break flood waves in X-T and R-T space." Thesis, University of Strathclyde, 1986. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=21480.
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The techniques for computing dam-break flood waves in prismatic channels are reviewed. Numerical models for cases with or without an initially dry downstream bed are developed. The models are based on the characteristic forms of the shallow water equations, both in (X-T) and (R-T) space, using specified time intervals and incorporating the Rankine-Hugoniot shock equations. Three numerical models for rectangular section channels are studied, namely the parallel (X-T), the expanded (R-T) and the contracted (R-T) cases; any two of these are then linked to produce three further models, described as the Contracted-Plain (RT-XT), the Contracted-Expanded (RT-RT) and the Plain-Expanded (XT-RT) models. Four physical models were tested and compared with results from the numerical models and with those from Barr and Das (1980), Marshall and Menendez (1981) and Katopodes and Schamber (1983). The numerical and experimental results are given in the form of comparative plots of front heights, surface profiles, front trajectories and depth hydrographs. Variations from the well-known solutions by Ritter (1892) and Stoker (1957), including those caused by radial flow effects are found to occur and are discussed.
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Puay, How Tion. "Fundamental Characteristics of Fluidable Material Dam Break Flow with Finite Extent and Its Application." 京都大学 (Kyoto University), 2009. http://hdl.handle.net/2433/120833.
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Bhandari, Manahari. "ONE-DIMENSIONAL (1D) & TWO-DIMENSIONAL (2D) DAM BREAK ANALYSIS AND COMPARISON OF DIFFERENT BREACHING PARAMETERS USING HEC-RAS." OpenSIUC, 2017. https://opensiuc.lib.siu.edu/theses/2175.
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Dam failure mechanism produces the rapidly varied unsteady flow situation and the appropriate analysis to determine the flow condition is necessary. Over the world, more than 80,000 dams were constructed. There have been more than 200 distinguished dam failures occurred within the twentieth century. The history of dam construction exists together with the probability of dam failure causing casualties and catastrophic situations. As climate change effect has caused the change in flow situations, the safety concern in the dam is also necessary. Casualties and damages due to dam break events depend upon the depth, flow velocity, population distribution as per geography and warning time related to the time to reach the peak flow to the downstream areas. Prediction of actual breaching scenario is not certain and is related to the geographical and geological features of the site, embankment type, type of breach, reservoir storage and flow conditions. Estimating the accurate breaching scenarios and modeling of the dam break situation to characterize the hydrodynamic risk is necessary. Among the numerous techniques of modeling dam break situation, this study focused on the use of HEC-RAS for analyzing the dam break situation. Most of the simulation of a dam break situation used one-dimensional analysis to solve flow conditions after the break of the dam. The Latest development of HEC-RAS 2D capabilities is also used in conjunction with 1D HEC-RAS dam break analysis to compare and explore both analysis capabilities of HEC-RAS. The effect of HEC-RAS simulation altering the breaching conditions is analyzed for the dam failure case of Big Bay dam located in Lamar County, Mississippi. The study area is chosen to obtain the simulation of piping dam failure, which was the real cause of the dam failure event. In addition, the overtopping failure parameters established by the different breaching regression equations were analyzed. Results obtained with both one- dimensional and two- dimensional analysis is compared along with the modeling procedure and concept of analysis. From the analysis, it is found that the time of peak water surface elevation and its magnitude is responsible in determining the extent of vulnerable areas to the dam break scenarios. The present study showed the variation in peak flow condition between different breach parameters. Breach bottom width found to be more sensitive parameters in dam failure events. HEC-RAS analysis is found to be suitable to predict the uncertain hydraulic behavior of dam break situation.
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Khan, Fayaz A. "Two-dimensional shock capturing numerical simulation of shallow water flow applied to dam break analysis." Thesis, Loughborough University, 2010. https://dspace.lboro.ac.uk/2134/7750.
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With the advances in the computing world, computational fluid dynamics (CFD) is becoming more and more critical tool in the field of fluid dynamics. In the past few decades, a huge number of CFD models have been developed with ever improved performance. In this research a robust CFD model, called Riemann2D, is extended to model flow over a mobile bed and applied to a full scale dam break problem. Riemann2D, an object oriented hyperbolic solver that solves shallow water equations with an unstructured triangular mesh and using high resolution shock capturing methods, provides a generic framework for the solution of hyperbolic problems. The object-oriented design of Riemann2D has the flexibility to apply the model to any type of hyperbolic problem with the addition of new information and inheriting the common components from the generic part of the model. In a part of this work, this feature of Riemann2D is exploited to enhance the model capabilities to compute flow over mobile beds. This is achieved by incorporating the two dimensional version of the one dimensional non-capacity model for erodible bed hydraulics by Cao et al. (2004). A few novel and simple algorithms are included, to track the wet/dry and dry/wet fronts over abruptly varying topography and stabilize the solution while using high resolution shock capturing methods. The negative depths computed from the surface gradient by the limiters are algebraically adjusted to ensure depth positivity. The friction term contribution in the source term, that creates unphysical values near the wet/dry fronts, are resolved by the introduction of a limiting value for the friction term. The model is validated using an extensive variety of tests both on fixed and mobile beds. The results are compared with the analytical, numerical and experimental results available in the literature. The model is also tested against the actual field data of 1957 Malpasset dam break. Finally, the model is applied to simulate dam break flow of Warsak Dam in Pakistan. Remotely sensed topographic data of Warsak dam is used to improve the accuracy of the solution. The study reveals from the thorough testing and application of the model that the simulated results are in close agreement with the available analytical, numerical and experimental results. The high resolution shock capturing methods give far better results than the traditional numerical schemes. It is also concluded that the object oriented CFD model is very easy to adapt and extend without changing the generic part of the model.
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LaBine, Anne M. "An experimental investigation of pressure of a simple dam break generated wave impacting a plate." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98970.
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Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (page 51).
It is desirable to measure pressure of a wave striking a vertical surface because this information can be used to determine the strength needed in the building materials of marine structures that may be struck by tall waves. These waves may be caused by storms, tsunamis, or dam breaks and can cause serious damage. This thesis presents two experiments aimed at measuring the pressure exerted by a wave. In both experiments, a series of water waves are released from a reservoir. One wave is released at a time and the waves vary in the initial height of water in the reservoir. In the first experiment, pressure is calculated using a force sensor to determine the force on a paddle and a high-speed camera to determine the contact area. It was found that wave pressure increases as the initial height increases. The pressures ranged from 5+/-2kPa at 25+/-1cm initial water height and 12+/-2kPa at 45+/-1cm initial water height. In the second experiment, pressure is measured at multiple vertical and horizontal locations on a vertical cantilevered plate. A sensor located in the middle of the plate horizontally and 1.25in from the bottom recorded the highest maximum pressure for all trials. The pressures from this sensor for this experiment ranged from 1.6+/-0.1kPa at 20+/-1cm initial water height and 7.4+/-.4kPa at 45+/-1cm initial water height.
by Anne M. LaBine.
S.B.
22
St-Germain, Philippe. "Numerical Modeling of Tsunami-induced Hydrodynamic Forces on Free-standing Structures Using the SPH Method." Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23527.
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Tsunamis are among the most terrifying and complex physical phenomena potentially affecting almost all coastal regions of the Earth. Tsunami waves propagate in the ocean over thousands of kilometres away from their generating source at considerable speeds. Among several other tsunamis that occurred during the past decade, the 2004 Indian Ocean Tsunami and the 2011 Tohoku Tsunami in Japan, considered to be the deadliest and costliest natural disasters in the history of mankind, respectively, have hit wide stretches of densely populated coastal areas. During these major events, severe destruction of inland structures resulted from the action of extreme hydrodynamic forces induced by tsunami flooding. Subsequent field surveys in which researchers from the University of Ottawa participated ultimately revealed that, in contrast to seismic forces, such hydrodynamic forces are not taken into proper consideration when designing buildings for tsunami prone areas. In view of these limitations, a novel interdisciplinary hydraulic-structural engineering research program was initiated at the University of Ottawa, in cooperation with the Canadian Hydraulic Centre of the National Research Council, to help develop guidelines for the sound design of nearshore structures located in such areas.
The present study aims to simulate the physical laboratory experiments performed within the aforementioned research program using a single-phase three-dimensional weakly compressible Smoothed Particle Hydrodynamics (SPH) numerical model. These experiments consist in the violent impact of rapidly advancing tsunami-like hydraulic bores with individual slender structural elements. Such bores are emulated based on the classic dam-break problem. The quantitatively compared measurements include the time-history of the net base horizontal force and of the pressure distribution acting on columns of square and circular cross-sections, as well as flow characteristics such as bore-front velocity and water surface elevation. Good agreement was obtained. Results show that the magnitude and duration of the impulsive force at initial bore impact depend on the degree of entrapped air in the bore-front. The latter was found to increase considerably if the bed of the experimental flume is covered with a thin water layer of even just a few millimetres.
In order to avoid large fluctuations in the pressure field and to obtain accurate simulations of the hydrodynamic forces, a Riemann solver-based formulation of the SPH method is utilized. However, this formulation induces excessive numerical diffusion, as sudden and large water surface deformations, such as splashing at initial bore impact, are less accurately reproduced. To investigate this particular issue, the small-scale physical experiment of Kleefsman et al. (2005) is also considered and modeled.
Lastly, taking full advantage of the validated numerical model to better understand the underlying flow dynamics, the influence of the experimental test geometry and of the bed condition (i.e. dry vs. wet) is investigated. Numerical results show that when a bore propagates over a wet bed, its front is both deeper and steeper and it also has a lower velocity compared to when it propagates over a dry bed. These differences significantly affect the pressure distributions and resulting hydrodynamic forces acting on impacted structures.
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Pohl, Reinhard, and Antje Bornschein. "Risiken, die von Stauanlagen ausgehen." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-160774.
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Eigentümer und Betreiber von Anlgen mit einem großen Gefahrenpotential sind gehalten, den zuständigen Behörden Auskunft über mögliche Folgen eines Störfalles zu erteilen. Für den unwahrscheinlichen Fall des Bruches eines Absperrrbauwerkes können diesbezügliche Informationen erarbeitet werden.
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Horna, Munoz Daniel Vicente. "Investigation of floodwave propagation over natural bathymetry using a three-dimensional numerical model." Diss., University of Iowa, 2017. https://ir.uiowa.edu/etd/5948.
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The current standard of simulating flood flow in natural river reaches is based on solving the 1-D or 2-D St. Venant equations or using hybrid 1-D/2-D models based on the same equations. These models are not always able to accurately predict floodwave propagation, especially around and downstream of regions where 3-D effects become important, or at times when the main assumptions associated with these models are violated (e.g. flow becomes pressurized due to presence of a hydraulic structure like a bridge or a culvert). A 3-D modeling approach, though computationally much more expensive, is not subject to such limitations and should be able to predict accurately predict floodwave propagation even in regions where 3-D effects are expected to be significant. This dissertation describes the development and validation of a 3-D time-accurate RANS-based model to study flood-related problems in natural environments. It also discusses how results from these 3-D simulations can be used to better calibrate lower order models. Applications are included where the flow becomes pressurized during high flow conditions and the sediment entrainment potential of the flow during the flooding event is estimated. Another important category of applications discussed in the present study are floodwave propagation induced by a sudden dam break failure. Results show that 2-D models show fairly large differences with 3-D model predictions especially in regions where 3-D effects are expected to be significant (e.g. near channel-floodplain transition, in highly curved channels, near hydraulic structures). The study also discusses the use of the validated 3-D model as an engineering design tool to identify the optimum solution for flood protection measures intended to reduce flooding in the Iowa River near Iowa City. 3-D simulation results are also used to discuss hysteresis effects in the relationship between bed shear stress and the stage/discharge. Such effects need to be taken into consideration to accurately estimate erosion associated with the passage of a floodwave.
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Adegoke, P. B. "An empirical study of flood wave impact pressures to determine the effectiveness of new seawall designs using a dam-break approach." Thesis, Liverpool John Moores University, 2014. http://researchonline.ljmu.ac.uk/4578/.
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Coastal flooding and erosion, a major consequence of coastal natural events can result in physical devastation, threats to human health and safety, detrimental effects on ecosystems, and severe economic losses to individuals and to society. These potentially devastating consequences are therefore justifying efforts to reduce both their occurrence and severity. Seawalls of varying slopes with wave energy dissipaters to create various degrees of roughness on their surfaces have been proposed as a potential evolution in the design of coastal defences. This present study therefore aimed at investigating the energy dissipating ability, in terms of impact pressures, of newly designed seawalls which incorporate unique energy dissipaters, with the ultimate goal of predicting the effectiveness of these new designs. To achieve these aims, a novel technique for generating floodwater waves has been developed and applied to new seawall models. A Low Cost Wave Tank (LCWT) with water release gate mechanism (dam-break method) was primarily designed and constructed for this purpose. Apart from the smooth surface wall model, geo-grid materials of varying textures and grit sizes have been used to model different degrees of surface roughness with each model subjected to varying wave heights and wall angles. The experimental tool and technique had been found to be effective and relatively economical while the gate release system represented a good approximation of instantaneous dam-break problem. The innovative imaging system (IS) and the sensor signal capture (SSC) techniques used for estimating flow velocity were found to be in close agreement with the commonly used PIV method, thus, could be a useful laboratory scheme for analysing hydrodynamics model studies. The study has also found the location of maximum impact pressures for the vertically inclined smooth surface wall model, to be varied from that of sloping forms which is in agreement with the propositions of most previous researchers. The maximum impact pressures have been found to be about 1.4 to 40 times the hydrostatic pressure which is within the range previously suggested by other researchers. Also, angle 75o appeared to be the best sloping position for the wall models investigated and in general, IMACTS wall seemed the most superior surface in terms of energy dissipation in vertical form. This implies that the harder the surface of the defence wall or/and the higher the degree of surface roughness the greater the energy of the floodwater waves that would be dissipated. Again, the predictive model equations proposed in this study are useful for the purposes of assessment of the suitability of the seawalls and the mitigation against flood hazards.
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Bornschein, Antje. "Gefahrenkarten - ein Instrument zur Risikoabschätzung infolge eines hypothetischen Talsperrenbruches." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2007. http://nbn-resolving.de/urn:nbn:de:swb:14-1173095576188-87738.
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Dam failures and the following emptying of the reservoir are very seldom. But such catastrophes caused significant damages in the past. The related risk has to consider as high despite the high return period. The paper describes the development of hazard maps showing the dimension of inundation in the downstream region of the dam due to a potential failure. The needed data and possible used software for the dam break flood simulation were discussed. A dam break occurred in the catchment area of the Müglitz river in the Ore mountains during the flood 2002 is describedDas Versagen einer Talsperre mit einer sich anschließenden Entleerung des Stauraumes ist sehr selten. Jedoch zogen solche Ereignisse in der Vergangenheit immer große Schäden nach sich, so dass trotz der geringen Eintrittswahrscheinlichkeit das Risiko als hoch einzuschätzen ist. Der Beitrag behandelt die Erstellung von Gefahrenkarten, die Auskunft darüber geben, wie groß die zu erwartende Überflutung infolge eines Bruches eines Absperrbauwerkes sein könnte. Dabei soll auf die zu ermittelnden Ausgangsdaten ebenso wie auf die zur Verfügung stehende Software zur Simulation der Ausbreitung von Talsperrenbruchwellen eingegangen werden. Als Fallbeispiel wird auf einen Dammbruch während des Hochwassers 2002 im Einzugsgebiet der Müglitz im Erzgebirge eingegangen
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Leite, Leandro de Oliveira Barbosa [UNESP]. "Determinação física e numérica de corridas de lama resultantes de ruptura de barreira retendo material viscoplástico." Universidade Estadual Paulista (UNESP), 2009. http://hdl.handle.net/11449/88862.
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Rompimentos de Barreira são fenômenos caracterizados por um campo de escoamento inicialmente represado e submetido nos instantes subseqüentes a uma liberação abrupta. Diversos modelos matemáticos e leis de comportamento reológico podem ser associados a este problema e cada um deles deve ser estudado e compreendido de maneira a predizer, a partir de testes físicos e numéricos, sua adequação à descrição da evolução espaço-temporal de frentes resultantes deste fenômeno, tipo ruptura de barragem, retendo água , rejeitos ou materiais de reologia complexa. O desenvolvimento de técnicas analíticas possibilitou entender de maneira impar o desenvolvimento desses fenômenos, porém, a difícil obtenção de dados que alcançassem consonância com aqueles obtidos experimentalmente, demonstrava a fragilidade desse tipo de análise perante a descrição de sistemas dinâmicos complexos. Sendo assim, optou-se pela tentativa de recriar estes fenômenos a partir de técnicas que utilizassem a manipulação de equações governantes completas. Sistemas contínuos podem ser analisados através de aproximações discretas, resultando em valores realísticos, muito próximos aos obtidos experimentalmente, e a capacidade computacional atual, permite diminuir sensivelmente os erros envolvidos, aumentando cada vez mais a consistência física destes métodos. Neste trabalho utilizou-se o software comercial ANSYS-CFX para simular os fenômenos de ruptura de barreira, configurando a reologia de dois materiais, o Carbopol 940 representando um material de reologia complexa (Herschel-Bulkley) e o Glicerol (Newtoniano), esses dados foram então confrontados com os obtidos experimentalmente através de um modelo em escala reduzida. Campos de velocidade, pressão e evolução temporal das frentes foram analisadas, verificando-se valores com grande consonância entre numérico e experimental, mostrando uma grande consistência física dos métodos utilizados
The Dam Break problem is a phenomenon characterized by a flow field initially dammed and submitted in the subsequent moments of an abrupt release. Various mathematical models and laws of rheological behavior may be associated with this type of problem and each must be studied and understood in order to predict from physical and numerical tests the temporal evolution of their fronts resulting from this phenomenon, type Dan Break problems, retaining water or rheology complex materials. The development of analytical techniques enabled the understanding the development of these phenomena, however, the difficulty to obtain a reach agreement data with those obtained experimentally, showed the fragility of this type of analysis to the description of complex dynamic systems. But, it was decided by attempt of recreate these phenomena from techniques that use the manipulation of complete government equations. Continuous systems can be analyzed by discrete approximations, leading to realistic values, very close to those obtained experimentally, and current computational capacity, enables to reduce the errors involved significantly, increasing the consistency of these physical methods. This work used the commercial software ANSYSCFX to simulate the phenomena of breaking the barrier, setting the rheology of two materials, the Carbopol 940 representing a material of complex rheology (Herschel-Bulkley) and glycerol (Newtonian), these data were then compared with those obtained experimentally using a model in scale. Fields of velocity, pressure and temporal evolution of the fronts were analyzed. Found very similar values between numerical and experimental simulations, showing the physical consistency of the methods used
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Pohl, Reinhard, and Antje Bornschein. "Risiken, die von Stauanlagen ausgehen." Technische Univeristät Dresden, 2007. https://tud.qucosa.de/id/qucosa%3A28541.
Full textAbstract:
Eigentümer und Betreiber von Anlgen mit einem großen Gefahrenpotential sind gehalten, den zuständigen Behörden Auskunft über mögliche Folgen eines Störfalles zu erteilen. Für den unwahrscheinlichen Fall des Bruches eines Absperrrbauwerkes können diesbezügliche Informationen erarbeitet werden.
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Leite, Leandro de Oliveira Barbosa. "Determinação física e numérica de corridas de lama resultantes de ruptura de barreira retendo material viscoplástico /." Ilha Solteira : [s.n.], 2009. http://hdl.handle.net/11449/88862.
Full textAbstract:
Orientador: Geraldo de Freitas MacielBanca: Cassio Roberto Macedo Maia
Banca: Mônica Feijó Naccache
Resumo: Rompimentos de Barreira são fenômenos caracterizados por um campo de escoamento inicialmente represado e submetido nos instantes subseqüentes a uma liberação abrupta. Diversos modelos matemáticos e leis de comportamento reológico podem ser associados a este problema e cada um deles deve ser estudado e compreendido de maneira a predizer, a partir de testes físicos e numéricos, sua adequação à descrição da evolução espaço-temporal de frentes resultantes deste fenômeno, tipo ruptura de barragem, retendo água , rejeitos ou materiais de reologia complexa. O desenvolvimento de técnicas analíticas possibilitou entender de maneira impar o desenvolvimento desses fenômenos, porém, a difícil obtenção de dados que alcançassem consonância com aqueles obtidos experimentalmente, demonstrava a fragilidade desse tipo de análise perante a descrição de sistemas dinâmicos complexos. Sendo assim, optou-se pela tentativa de recriar estes fenômenos a partir de técnicas que utilizassem a manipulação de equações governantes completas. Sistemas contínuos podem ser analisados através de aproximações discretas, resultando em valores realísticos, muito próximos aos obtidos experimentalmente, e a capacidade computacional atual, permite diminuir sensivelmente os erros envolvidos, aumentando cada vez mais a consistência física destes métodos. Neste trabalho utilizou-se o software comercial ANSYS-CFX para simular os fenômenos de ruptura de barreira, configurando a reologia de dois materiais, o Carbopol 940 representando um material de reologia complexa (Herschel-Bulkley) e o Glicerol (Newtoniano), esses dados foram então confrontados com os obtidos experimentalmente através de um modelo em escala reduzida. Campos de velocidade, pressão e evolução temporal das frentes foram analisadas, verificando-se valores com grande consonância entre numérico e experimental, mostrando uma grande consistência física dos métodos utilizados
Abstract: The Dam Break problem is a phenomenon characterized by a flow field initially dammed and submitted in the subsequent moments of an abrupt release. Various mathematical models and laws of rheological behavior may be associated with this type of problem and each must be studied and understood in order to predict from physical and numerical tests the temporal evolution of their fronts resulting from this phenomenon, type Dan Break problems, retaining water or rheology complex materials. The development of analytical techniques enabled the understanding the development of these phenomena, however, the difficulty to obtain a reach agreement data with those obtained experimentally, showed the fragility of this type of analysis to the description of complex dynamic systems. But, it was decided by attempt of recreate these phenomena from techniques that use the manipulation of complete government equations. Continuous systems can be analyzed by discrete approximations, leading to realistic values, very close to those obtained experimentally, and current computational capacity, enables to reduce the errors involved significantly, increasing the consistency of these physical methods. This work used the commercial software ANSYSCFX to simulate the phenomena of breaking the barrier, setting the rheology of two materials, the Carbopol 940 representing a material of complex rheology (Herschel-Bulkley) and glycerol (Newtonian), these data were then compared with those obtained experimentally using a model in scale. Fields of velocity, pressure and temporal evolution of the fronts were analyzed. Found very similar values between numerical and experimental simulations, showing the physical consistency of the methods used
Mestre
30
Castillo, Vargas Luis Arturo, and Vargas Italo Boris Castillo. "Generación de mapas de peligro producido por la simulación del vertido de relaves de la rotura de la presa N° 4 en el distrito de Carmen de Atrato en el departamento de Chocó – Colombia." Bachelor's thesis, Universidad Peruana de Ciencias Aplicadas (UPC), 2019. http://hdl.handle.net/10757/652388.
Full textAbstract:
La presente investigación se centra en la generación de mapas de peligro por la simulación del vertido de relaves por rotura de la presa del depósito de relaves en estado pulpa ubicada en el distrito de Chocó, en Colombia mediante un modelo hidrológico – hidráulico, y la posterior clasificación de los mapas de inundación y velocidad en niveles de peligrosidad.
Este tipo de simulaciones requieren de un modelo numérico capaz de analizar y desarrollar el comportamiento de un flujo hiperconcentrado en la llanura de inundación aguas abajo. Las ecuaciones que controlan el movimiento de estos tipos de flujos son las aplicadas para fluidos no newtonianos, los cuales están controlados por los parámetros reológicos, como: viscosidad dinámica, esfuerzo de fluencia y la tasa de corte. Es por ello que se ha escogido el software FLO-2D el cual cuenta con facilidad de ingreso de datos y geometría, estabilidad de rutina computacional y la facilidad de lectura de archivos de salida.
Los resultados obtenidos de la simulación en el distrito de Chocó muestran de manera didáctica la delimitación de zonas de riesgo de acuerdo a la clasificación de peligro en torno a velocidades y tirantes máximos. Eso nos permitió reconocer las estructuras que comprendidas en las zonas de alto riesgo.
Estos mapas de peligro servirán como herramientas para evaluaciones de alcance social, ambiental y económico y la consideración y elección de medidas a corto, mediano y largo plazo, y de carácter tanto estructural, como no estructural.This research focuses on the generation of hazard maps by simulating the discharge of tailings due to breakage of the dam of the pulp tailings deposit located in the Chocó district, in Colombia, using a hydrological-hydraulic model, and the subsequent classification of the flood and speed maps in danger levels. These types of simulations require a numerical model capable of analyzing and developing the behavior of a hyperconcentrated flow in the downstream floodplain. The equations that control the movement of these types of flows are those applied for non-Newtonian fluids, which are controlled by the rheological parameters, such as: dynamic viscosity, creep stress and the shear rate. That is why the FLO-2D software has been chosen which has ease of data entry and geometry, computational routine stability and ease of reading output files. The results obtained from the simulation in the Chocó district didactically show the delimitation of risk areas according to the hazard classification around maximum speeds and braces. This allowed us to recognize the structures included in high risk areas. These hazard maps will serve as tools for evaluations of social, environmental and economic scope and the consideration and choice of short, medium and long-term measures, both structural and non-structural.
Tesis
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Ferla, Rute. "Metodologia simplificada para análise de aspectos hidráulicos em rompimento de barragens." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2018. http://hdl.handle.net/10183/180112.
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O início da construção de estruturas para reserva de água no mundo é conhecido há milhares de anos, e, desde então, as barragens são consideradas alternativas viáveis não apenas para reserva de água para consumo, mas também para as finalidades de geração de energia hidrelétrica, contenção de rejeitos, entre outras. Entretanto, mesmo com os contínuos avanços nas técnicas construtivas e na fiscalização da segurança destas estruturas, a possibilidade de rompimento de barragens é uma realidade constante. Nesta perspectiva, o presente texto objetiva analisar os aspectos hidráulicos de metodologias simplificadas para estimativa de parâmetros de inundação proveniente do rompimento de barragens, a saber, as vazões e respectivas profundidades atingidas no vale a jusante, em um evento de rompimento hipotético. Para tal, analisaram-se os resultados de três metodologias simplificadas existentes, aplicadas em três barragens estudo de caso, com características estruturais e geometria do vale a jusante distintas. Os resultados das metodologias simplificadas foram comparados com os estudos de Dam Break das três barragens estudo de caso, obtidos com o uso do software HEC-RAS unidimensional e cedidos por empreendedores. O presente texto também sugere uma nova equação empírica para previsão da vazão máxima resultante do rompimento de barragens por galgamento, e propõe uma nova metodologia simplificada para análise preliminar de rompimento de barragens, com base nos métodos analisados e nas respectivas conclusões obtidas. Os resultados indicam que o uso de metodologias simplificadas na análise preliminar de rompimento de barragens é uma alternativa viável em vales cuja declividade do talvegue é acentuada e cujas características geométricas são aproximadamente constantes. Identificou-se que pequenas alterações no coeficiente de rugosidade do terreno e na declividade da linha de energia refletiram em diferenças nos resultados de profundidades e larguras máximas de 20%, em média. A proposta de nova equação empírica para previsão de vazão máxima na seção da barragem baseou-se na análise de 39 casos reais envolvendo ruptura de barragens por galgamento e resultou em um coeficiente de determinação (R²) de 0,79. Quando comparada com as principais equações semelhantes indicadas na bibliografia, a equação proposta obteve vazões máximas próximas ou superiores às dos demais pesquisadores analisados sempre que a altura da barragem foi inferior a 30 m. Evidencia-se a importância na estimativa cautelosa da vazão máxima na seção da barragem, uma vez que essa reflete em diferenças significativas nas vazões e respectivas profundidades alcançadas ao longo do vale a jusante da estrutura. Nos casos analisados, diferentes vazões máximas na seção da barragem refletiram em distinções de até 50%, em média, nas profundidades e larguras máximas a jusante. A nova metodologia proposta para definição de características de inundação provenientes do rompimento de barragens pode contribuir em estudos preliminares para tal, especialmente aos empreendedores que possuem número expressivo de barragens. Nesses casos, a metodologia poderá nortear a prioridade a ser dada em estudos detalhados de Dam Break.For thousands of years, water reservoir structures have been built worldwide. Since then, dams have been considered viable alternatives not only for reserving water for consumption but also for the purposes of hydroelectric power generation and sediment retention, among others. Despite the continuous advances in the construction techniques and in the safety inspection of these structures, the possibility of breaking of dams remains a constant reality. Hence, this paper aims to analyze the hydraulic aspects of simplified methodologies for estimating flood parameters on dam ruptures, namely, the flows and respective depths reached in the downstream valley in a hypothetical breach event. Results of three existing simplified methodologies were studied applied in three dams with different structural characteristics and downstream valley geometry. The results of simplified methodologies were compared with dam break studies of three study case dams, obtained with one-dimensional HEC-RAS and provided by entrepreneurs. The present paper suggests also a new empirical equation for predicting the maximum flow resulting from the overtopping dam failure and proposes a new simplified methodology for preliminary analysis of dam rupture, based on the analyzed methods and respective obtained conclusions. The results indicate that the use of simplified methodologies in the preliminary dam break analysis is a viable alternative in valleys with high thalweg declivities and close to constant geometric characteristics. It was identified that small changes in the coefficient of rough terrain and in the energy line slope reflected in differences in the results of depths and maximum widths of 20%, on average. The proposed new empirical equation for maximum flow prediction in the dam section was based on the analysis of 39 actual cases involving overtopping dam failure and resulted in a coefficient of determination (R²) of 0.79. When compared to similar main equations indicated in the bibliography, the proposed equation obtained maximum flows near or higher than those of other researchers analyzed whenever the height of the dam did not exceed 30 m. The importance of a cautious estimation of the maximum flow rate in the dam section is to be highlighted, since it results in significant variations of flow and respective depths along the valley and downstream of the structure. Different maximum flows were found in the dam section, which reflected in distinctions of up to 50%, in average, in the maximum depths and widths downstream. The new proposed methodology for defining dam break characteristics caused by dam rupture may contribute to preliminary studies, especially to entrepreneurs who own a significant number of dams. In these cases, the methodology may guide the priority to be given in detailed studies of dam break.
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Minussi, Roberta Brondani [UNESP]. "Rompimento de barreiras: análise experimental e numérica na previsão de velocidades de propagação de frentes de material hiperconcentrado." Universidade Estadual Paulista (UNESP), 2007. http://hdl.handle.net/11449/88874.
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Denominam-se problemas tipo rompimento de barreira os fenômenos nos quais um fluido é liberado de maneira abrupta. Quando o fluido apresenta natureza hiperconcentrada, a relação entre a tensão de cisalhamento e a taxa de deformação pode se tornar não-linear, passando a apresentar reologia não-Newtoniana. Problemas deste tipo podem ser encontrados em muitos fenômenos tanto na natureza quanto em processos industriais. O estudo de tal problema é, geralmente, conduzido usando simplificações, como a aproximação de águas rasas e a separação do escoamento em regimes dominantemente inerciais ou viscosos. O presente trabalho é composto de duas partes, uma experimental e outra, numérica. No campo experimental, duas soluções controladas são usadas: soluções aquosas de açúcar e de Carbopol 940, esta última com várias concentrações volumétricas. O aparato experimental consiste em um canal retangular de acrílico, contendo uma comporta, a montante da qual, o fluido é retido e, pela ruptura (levantamento da comporta), começa a escoar. O escoamento é estudado através de técnicas avançadas de filmagem. No campo numérico, são realizadas simulações usando o programa CFX, no qual é usado um método de rastreamento de interface, o VOF e sem o emprego das simplificações citadas. Os resultados experimentais são comparados com os numéricos e com resultados da literatura que usam tais simplificações. Na comparação a aproximação de águas rasas, apesar de descrever bem a forma da interface, se distancia dos valores reais da posição da frente de onda.
The dam break problem describes a phenomenon in which there is an abrupt release of fluid. When the fluid is hiperconcentrated, the relation between the shear stress and the strain rate can become non-linear, and so present a non-Newtonian rheology. The non-Newtonian dam break problem may be found in many phenomena in nature and industrial process. The study of such a problem is, generally, conducted using simplified hypothesis such as the shallow water approximation and the separation of the flow in inertial and viscous dominated regimes. The present work is composed of two parts, one experimental and other, numerical. In the experimental field, two controlled solutions were used: water solutions of sugar and of Carbopol 940, the last one with a wide range of volume concentrations. These fluids have, respectively, Newtonian and non-Newtonian rheologies. The experimental setup consists of an acrylic rectangular channel, which has a dam and upstream of that the fluid is retained and, by the rupture, it begins to flow. The flow is studied by using advanced filming techniques. In the numerical field, simulations are conducted using the CFX software, which uses an interface tracking method, the VOF, and without the shallow water approximation and the division of the flow. So the experimental, numerical and literature results, that uses such simplifications, are compared and it is showed that the shallow water approximation, however describes very well the shape of the surface, is not accurate in calculate the wave front position.
33
Lee, Haegyun. "Level-set finite element simulation of free-surface flow." Diss., University of Iowa, 2007. http://ir.uiowa.edu/etd/168.
Full text
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Minussi, Roberta Brondani. "Rompimento de barreiras : análise experimental e numérica na previsão de velocidades de propagação de frentes de material hiperconcentrado /." Ilha Solteira : [s.n.], 2007. http://hdl.handle.net/11449/88874.
Full textAbstract:
Orientador: Geraldo de Freitas MacielBanca: Sérgio Said Mansur
Banca: Jean Paul Vila
Resumo: Denominam-se problemas tipo rompimento de barreira os fenômenos nos quais um fluido é liberado de maneira abrupta. Quando o fluido apresenta natureza hiperconcentrada, a relação entre a tensão de cisalhamento e a taxa de deformação pode se tornar não-linear, passando a apresentar reologia não-Newtoniana. Problemas deste tipo podem ser encontrados em muitos fenômenos tanto na natureza quanto em processos industriais. O estudo de tal problema é, geralmente, conduzido usando simplificações, como a aproximação de águas rasas e a separação do escoamento em regimes dominantemente inerciais ou viscosos. O presente trabalho é composto de duas partes, uma experimental e outra, numérica. No campo experimental, duas soluções controladas são usadas: soluções aquosas de açúcar e de Carbopol 940, esta última com várias concentrações volumétricas. O aparato experimental consiste em um canal retangular de acrílico, contendo uma comporta, a montante da qual, o fluido é retido e, pela ruptura (levantamento da comporta), começa a escoar. O escoamento é estudado através de técnicas avançadas de filmagem. No campo numérico, são realizadas simulações usando o programa CFX, no qual é usado um método de rastreamento de interface, o VOF e sem o emprego das simplificações citadas. Os resultados experimentais são comparados com os numéricos e com resultados da literatura que usam tais simplificações. Na comparação a aproximação de águas rasas, apesar de descrever bem a forma da interface, se distancia dos valores reais da posição da frente de onda.
Abstract: The dam break problem describes a phenomenon in which there is an abrupt release of fluid. When the fluid is hiperconcentrated, the relation between the shear stress and the strain rate can become non-linear, and so present a non-Newtonian rheology. The non-Newtonian dam break problem may be found in many phenomena in nature and industrial process. The study of such a problem is, generally, conducted using simplified hypothesis such as the shallow water approximation and the separation of the flow in inertial and viscous dominated regimes. The present work is composed of two parts, one experimental and other, numerical. In the experimental field, two controlled solutions were used: water solutions of sugar and of Carbopol 940, the last one with a wide range of volume concentrations. These fluids have, respectively, Newtonian and non-Newtonian rheologies. The experimental setup consists of an acrylic rectangular channel, which has a dam and upstream of that the fluid is retained and, by the rupture, it begins to flow. The flow is studied by using advanced filming techniques. In the numerical field, simulations are conducted using the CFX software, which uses an interface tracking method, the VOF, and without the shallow water approximation and the division of the flow. So the experimental, numerical and literature results, that uses such simplifications, are compared and it is showed that the shallow water approximation, however describes very well the shape of the surface, is not accurate in calculate the wave front position.
Mestre
35
Rondon, Loic. "Effondrement granulaire : couplages fluide-grains." Thesis, Aix-Marseille 1, 2011. http://www.theses.fr/2011AIX10209/document.
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Nous étudions expérimentalement l'effondrement d'une colonne granulaire dans un liquide visqueux. Contrairement au cas sec, la morphologie des dépôts n'est principalement plus contrôlée par le rapport d'aspect initial du tas mais par la fraction volumique initiale de la masse granulaire. Deux régimes différents sont identifiés selon l'empilement initial. L'empilement lâche donne lieu à des dépôts minces et longs et la dynamique est rapide. Une surpression du liquide est mesurée sous de la colonne. Pour l'empilement dense, l'étalement final est deux fois moindre, le mouvement est lent et une dépression interstitielle est mesurée. Ces observations suggèrent que la dynamique de l'effondrement granulaire dans un fluide est fortement affectée par le comportement de la dilatance du milieu granulaire.Nous développons ensuite un modèle théorique basé sur des équations diphasiques moyennées dans l’épaisseur prenant en compte les mécanismes de dilatance. L’étude dimensionnelle de notre modèle permet de montrer que l’effondrement d’une colonne est contrôlé par trois paramètres sans dimension : le rapport d’aspect de la colonne, la fraction volumique initiale, et le nombre de grains dans l’épaisseur. On montre également que le temps caractéristique met en compétition le frottement visqueux et la gravité.De ce modèle, nous développons un algorithme de résolution lagrangien. Cette approche, grossière mais robuste, permet d’implanter s sans trop de difficulté. Le code est validé sur des configurations simples sur plan incliné avant de simuler l’effondrement de colonnes granulaires immergées dans la même gamme de paramètres que nos expériencesNous étudions expérimentalement l'effondrement d'une colonne granulaire dans un liquide visqueux. Contrairement au cas sec, la morphologie des dépôts n'est principalement plus contrôlée par le rapport d'aspect initial du tas mais par la fraction volumique initiale de la masse granulaire. Deux régimes différents sont identifiés selon l'empilement initial. L'empilement lâche donne lieu à des dépôts minces et longs et la dynamique est rapide. Une surpression du liquide est mesurée sous de la colonne. Pour l'empilement dense, l'étalement final est deux fois moindre, le mouvement est lent et une dépression interstitielle est mesurée. Ces observations suggèrent que la dynamique de l'effondrement granulaire dans un fluide est fortement affectée par le comportement de la dilatance du milieu granulaire.Nous développons ensuite un modèle théorique basé sur des équations diphasiques moyennées dans l’épaisseur prenant en compte les mécanismes de dilatance. L’étude dimensionnelle de notre modèle permet de montrer que l’effondrement d’une colonne est contrôlé par trois paramètres sans dimension : le rapport d’aspect de la colonne, la fraction volumique initiale, et le nombre de grains dans l’épaisseur. On montre également que le temps caractéristique met en compétition le frottement visqueux et la gravité.De ce modèle, nous développons un algorithme de résolution lagrangien. Cette approche, grossière mais robuste, permet d’implanter s sans trop de difficulté. Le code est validé sur des configurations simples sur plan incliné avant de simuler l’effondrement de colonnes granulaires immergées dans la même gamme de paramètres que nos expériences
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Gonzalez-Ramirez, Noemi. "Simulating Flood Propagation in Urban Areas using a Two-Dimensional Numerical Model." Scholarly Repository, 2010. http://scholarlyrepository.miami.edu/oa_dissertations/648.
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A two-dimensional numerical model (RiverFLO-2D) has been enhanced to simulate flooding of urban areas by developing an innovative wet and dry surface algorithm, accounting for variable rainfall, and recoding the model computer program for parallel computing. The model formulation is based on the shallow water equations solved with an explicit time-stepping element-by-element finite element method. The dry-wet surface algorithm is based on a local approximation of the continuity and momentum equations for elements that are completely dry. This algorithm achieves global volume conservation in the finite element, even for flows over complex topographic surfaces. A new module was implemented to account for variable rainfall in space and time using NEXRAD precipitation estimates. The resulting computer code was parallelized using OpenMP Application Program Interface, which allows the model to run up to 5 times faster on multiple core computers. The model was verified with analytical solutions and validated with laboratory and field data. Model application to the Malpasset dam break and Sumacarcel flooding event show that the model accurately predicts flood wave travel times and water depths for these numerically demanding real cases. To illustrate the predictive capability of the enhanced model, an application was made of the city of Sweetwater flooding in Miami-Dade County, FL caused by the Hurricane Irene. The simulation starts with dry bed and rainfall is provided by NEXRAD estimates. Integrating NEXRAD rainfall estimates, developing a novel dry-wet area algorithm and parallelizing RiverFLO-2D code, this dissertation presents a proof of concept to accurately and efficiently predict floods in urban areas, identifying future improvements along this line of research.
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Bonnet, Félix. "Déstabilisation gravitaire d'un matériau granulaire immergé." Thesis, Grenoble, 2012. http://www.theses.fr/2012GRENI026/document.
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La stabilité gravitaire des ouvrages hydrauliques (digues fluviales, barrage en remblai, ...) est un problème complexifié par la présence d'infiltration d'eau au sein même de l'ouvrage et de ses fondations. Le territoire national compte près de 10000 km de digues, d'où un enjeu important en terme de risque d'inondation. Les déstabilisations gravitaires observées sur les ouvrages hydrauliques se distinguent par leur brièveté et par leur faible emprise spatiale. L'objectif de ce travail de thèse est d'étudier spécifiquement ces instabilités brèves et de faible déplacement cumulé le long de la pente dans le cas de matériaux granulaires saturés. Dans un premier temps, une campagne expérimentale a été effectuée sur la base d'un protocole de chargement progressif dans lequel un échantillon de sol est lentement incliné jusqu'à obtenir une déstabilisation massive. Il en ressort une phénoménologie complexe composée d'un nombre de précurseurs d'avalanche dépendant de la fraction volumique de l'échantillon. Une forte influence de la fraction volumique du sol sur le seuil de stabilité est également mise en avant. Une deuxième campagne expérimentale basée sur un protocole d'effondrement contrôlé, à inclinaison imposée, a été menée dans le but d'amplifier la cinématique de déstabilisation observée en chargement progressif. Mis à part les échantillons les plus denses qui produisent de simples avalanches de surface, on observe dans les autres cas un ou plusieurs événements successifs, d'allure circulaire, mobilisant des profondeurs très importantes contrairement aux avalanches de surface.. Outre l'inclinaison, on voit bien que, là encore, la fraction volumique est un paramètre clé dans le contrôle de la cinématique de déstabilisation. Des essais préliminaires laissent cependant entendre que, au-delà de la fraction volumique, c'est la microstructure qui semble être le vrai paramètre de contrôle à travers notamment la forme des grains et leur enchevêtrementGravitational stability of hydraulic structures (river dykes, embankment dam,...) is a problem complicated by the presence of water infiltration within the structure and its foundations. Our country has about 10,000 km of dikes and gravitational failure is a major challenge in terms of flood risk. In hydraulic structures, these destabilizations are characterized by their brevity and their small spatial extent. The objective of this thesis is to study specifically this type of brief instabilities in the case of a saturated granular material. A first series of experiments was carried out on the basis of a progressive loading protocol in which a soil sample is tilted slowly until a massive destabilization is triggered. It shows a phenomenology complex consisting of a number of precursory events prior final avalanching, dependent on the solid volume fraction of the sample. A strong impact of the solid volume fraction of the soil on the stability threshold is also highlighted. A second series of experiments based on a protocol of collapse controlled at imposed slope was conducted to amplify the kinematics of destabilization observed by progressive loading. Apart from the denser samples that produce simple surface avalanches, one or more successive events are observed in other cases. Unlike surface avalanches, these events mobilize grains much deeper, in an almost semi-circular area. In addition to slope angle, solid volume fraction is once again a key parameter in controlling the kinematics of destabilization. Preliminary tests suggest, however, that, beyond solid volume fraction, microstructure appears to be the true control parameter, particularly through grain shape and texture
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Bougouin, Alexis. "Etude expérimentale de l'effondrement d'une colonne fluide-grains." Thesis, Toulouse, INPT, 2017. http://www.theses.fr/2017INPT0113/document.
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Autour de nous, les systèmes granulaires sont omniprésents et rarement dissociés d'une phase liquide ou gazeuse. L'interaction entre les deux phases (solide et fluide) implique une dynamique d'écoulement complexe de ces systèmes couplés. Cette thèse expérimentale a pour but de caractériser la dynamique d'effondrement gravitaire instationnaire d'une colonne fluide-grains dans différentes configurations de mélange diphasique. Considérant uniquement l'effet des grains au sein du fluide, la dynamique d'écoulement d'une suspension isodense dans l'air est d'abord abordée avec une description macroscopique. En particulier, La rhéologie du fluide apparent est extraite à partir de l'évolution temporelle du front en utilisant des solutions auto-similaires, modèles de la dynamique de propagation aux temps longs. Sur la gamme du nombre de Reynolds étudiée, la dynamique d'écoulement de la suspension est décrite comme celle d'un fluide apparent Newtonien ou non-Newtonien (rhéofluidifiant, rhéoépaississant, viscoplastique) dépendant des paramètres considérés (fraction volumique, viscosité du fluide interstitiel, diamètre des grains, protocole de préparation). Afin de décrire la configuration opposée d'un massif sédimentaire pour lequel les interactions entre particules solides deviennent dominantes, la configuration d'une colonne granulaire dense saturée en fluide, i.e. où les grains sont plus lourds que le fluide porteur, est ensuite étudiée. Un travail préliminaire est consacré à la caractérisation de l'effondrement d'une colonne granulaire totalement immergée dans un fluide. Le rôle dissipatif de ce dernier sur le milieu granulaire est mis en évidence par une analyse de la dynamique d'effondrement et des caractéristiques du dépôt final. Cette caractérisation permet de classifier les régimes d'effondrement en fonction de la viscosité et de la masse volumique du fluide environnant, i.e. du nombre de Stokes et du rapport de masse volumique entre le fluide et les grains. Dans le cas triphasique, i.e. lorsque la colonne fluide-grains s'effondre dans l'air, la dynamique peut être fortement affectée par les effets capillaires à travers le nombre de Bond qui contrôle alors la mise en mouvement de la colonne initiale. Quand ces effets deviennent négligeables à l'échelle de la colonne et à celle du grain, le fluide interstitiel peut jouer un rôle moteur ou dissipatif vis-à-vis dumilieu granulaire conduisant à une longueur d'étalement plus ou moins importante en comparaison au cas sec. Le rôle du fluide interstitiel dépend essentiellement de sa viscosité modifiant, par la même occasion, la dynamique d'effondrement. Enfin, une étude préliminaire sur la dynamique d'écoulement d'une suspension non-isodense, initialement homogène, est réalisée. Cette configuration, à la transition des situations décrites précédemment, permet d'aborder le couplage de la dynamique de sédimentation des grains et celle du courant. En particulier, nous observons que la vitesse de sédimentation décroît avec l'augmentation de la fraction volumiqueinitiale en particulesOn the Earth's surface, granular medias are ubiquitous and they are rarely dissociated from a liquid or a gas. The fluid-solid interaction leads to a complex flow dynamics of these coupled systems. This experimental work aims at characterizing the dynamics of the unsteady gravitydrivencollapse of a granular-fluid column within different configurations of the diphasic mixture. First, the flow dynamics of a neutrally buoyant suspension in air are characterized based on a macroscopic description of the flow. In particular, the rheological parameters of the apparent fluid have been extracted using the temporal evolution of the propagating front and self-similar solutions, models of the propagating dynamics at long times. In the considered range of the Reynolds number, the flow dynamics are described as an apparent Newtonian or non-Newtonian (shear-thinning/-thickening, viscoplastic) fluid depending on the various parameters (volume fraction, viscosity of the interstitial fluid, particle diameter, mixing protocol). In order to describe the opposite case of a sedimentary environment where particle-particle interaction becomes dominant, a second part of this work investigates the case of a fluid-saturated granular collapse, i.e. for which particles are heavier than the carrier fluid, in a dense packing configuration. For this purpose, a first part of the study is dedicated to characterize the collapse of an immersed granular column. The dissipative role of the fluid on the granular media is highlighted by an analysis of the collapse dynamics and the characteristics of the final deposit. This characterization allows to classify the regimes of the collapse depending on the viscosity and the density of the surrounding fluid, i.e. the Stokes number and the fluid-grain density ratio. In the triphasic case, i.e. when the granular-fluid column collapses in air, the dynamics may be strongly affected by capillary effects through the Bond number which controls the initial dynamics of the column. When these effects can be neglected (large Bond number) at the column and grain scales, the interstitial fluid can have a driven or a dissipative role on the granular media leading to a runout length more or less extended in comparison to the dry case. The role of the interstitial fluid depends mainly on its viscosity which also modifies the collapse dynamics. Finally, a preliminary study is realized on the flow dynamics of an initially homogeneous negative buoyant suspension column. This case, which makes the transition between the above mentioned configurations, allows to study the coupling between the settling dynamics of particles and this of the current. In particular, we observe that the settling velocity decreases with the increase of the initial volume fraction of particles
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Drui, Florence. "Modélisation et simulation Eulériennes des écoulements diphasiques à phases séparées et dispersées : développement d’une modélisation unifiée et de méthodes numériques adaptées au calcul massivement parallèle." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLC033/document.
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Dans un contexte industriel, l’utilisation de modèles diphasiques d’ordre réduit est nécessaire pour pouvoir effectuer des simulations numériques prédictives d’injection de combustible liquide dans les chambres de combustion automobiles et aéronautiques, afin de concevoir des équipements plus performants et moins polluants. Le processus d’atomisation du combustible, depuis sa sortie de l’injecteur sous un régime de phases séparées, jusqu’au brouillard de gouttelettes dispersées, est l’un des facteurs clés d’une combustion de bonne qualité. Aujourd’hui cependant, la prise en compte de toutes les échelles physiques impliquées dans ce processus nécessite une avancée majeure en termes de modélisation, de méthodes numériques et de calcul haute performance (HPC). Ces trois aspects sont abordés dans cette thèse. Premièrement, des modèles de mélange, dérivés par le principe variationnel de Hamilton et le second principe de la thermodynamique sont étudiés. Ils sont alors enrichis afin de pouvoir décrire des pulsations des interfaces au niveau de la sous-échelle. Des comparaisons avec des données expérimentales dans un contexte de milieux à bulles permettent de vérifier la cohérence physique des modèles et de valider la méthodologie. Deuxièmement, une stratégie de discrétisation est développée, basée sur une séparation d’opérateur, permettant la résolution indépendante de la partie convective des systèmes à l’aide de solveurs de Riemann approchés standards et les termes sources à l’aide d’intégrateurs d’équations différentielles ordinaires. Ces différentes méthodes répondent aux particularités des systèmes diphasiques compressibles, ainsi qu’au choix de l’utilisation de maillages adaptatifs (AMR). Pour ces derniers, une stratégie spécifique est développée : il s’agit du choix de critères de raffinement et de la projection de la solution d’une grille à une autre (plus fine ou plus grossière). Enfin, l’utilisation de l’AMR dans un cadre HPC est rendue possible grâce à la bibliothèque AMR p4est, laquelle a montré une excellente scalabilité jusqu’à plusieurs milliers de coeurs de calcul. Un code applicatif, CanoP, a été développé et permet de simuler des écoulements fluides avec des méthodes de volumes finis sur des maillages AMR. CanoP pourra être utilisé pour des futures simulations d’atomisation liquideIn an industrial context, reduced-order two-phase models are used in predictive simulations of the liquid fuel injection in combustion chambers and help designing more efficient and less polluting devices. The combustion quality strongly depends on the atomization process, starting from the separated phase flow at the exit of the nozzle down to the cloud of fuel droplets characterized by a disperse-phase flow. Today, simulating all the physical scales involved in this process requires a major breakthrough in terms of modeling, numerical methods and high performance computing (HPC). These three aspects are addressed in this thesis. First, we are interested in mixture models, derived through Hamilton’s variational principle and the second principle of thermodynamics. We enrich these models, so that they can describe sub-scale pulsations mechanisms. Comparisons with experimental data in a context of bubbly flows enables to assess the models and the methodology. Based on a geometrical study of the interface evolution, new tracks are then proposed for further enriching the mixture models using the same methodology. Second, we propose a numerical strategy based on finite volume methods composed of an operator splitting strategy, approximate Riemann solvers for the resolution of the convective part and specific ODE solvers for the source terms. These methods have been adapted so as to handle several difficulties related to two-phase flows, like the large acoustic impedance ratio, the stiffness of the source terms and low-Mach issues. Moreover, a cell-based Adaptive Mesh Refinement (AMR) strategy is considered. This involves to develop refinement criteria, the setting of the solution values on the new grids and to adapt the standard methods for regular structured grids to non-conforming grids. Finally, the scalability of this AMR tool relies on the p4est AMR library, that shows excellent scalability on several thousands cores. A code named CanoP has been developed and enables to solve fluid dynamics equations on AMR grids. We show that CanoP can be used for future simulations of the liquid atomization
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Moreno, E. (Elvira). "Elementos finitos mixtos estabilizados para flujos viscoplásticos." Doctoral thesis, Universitat Politècnica de Catalunya, 2014. http://hdl.handle.net/10803/246119.
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The objective of this thesis is to develop and evaluate a methodology for the solution of the Navier-Stokes equations for Bingham Herschel-Bulkley viscoplastic fluids using stabilized mixed velocity/pressure finite elements. The theoretical formulation is developed and implemented in a computer code. Numerical solutions for these viscoplastic flows are presented and assessed.
Viscoplastic fluids are characterized by minimum shear stress called yield stress. Above this yield stress, the fluid is able to flow. Below this yield stress, the fluid behaves as a quasi-rigid body, with zero strain-rate.
First, the Navier-Stokes equations for incompressible fluid and two immiscible fluids considering free surface are presented. A review of the Newtonian and non-Newtonian rheological models is included, with a detailed description of the viscoplastic models. The regularized viscoplastic models due to Papanastasiou are described. Double viscosity regularized models are proposed.
The analytical solutions for parallel flows are deduced for Newtonian, Bingham, and Herschel-Bulkley, pseudoplastic and dilatant fluids.
The discrete model is developed, and the Algebraic SubGrid Scale (ASGS) stabilization method, the Orthogonal Subgrid scale (OSS) method and the split orthogonal subscales method are introduced. For the cases of flows with a free surface, the simplified Eulerian method is employed, with the level set method to solve the motion of the free.
A convergence study is performed to compare the ASGS and OSS stabilization methods in parallel flows with Bingham and Herschel-Bulkley fluids. The double viscosity regularized models show lower convergence error convergence than the regularized models used commonly.
Numerical solutions developed in this thesis are applied to a broad set of benchmark problems. They can be divided into three groups: Bingham flows, Herschel-Bulkley flows and free surface flows.
The solutions obtained validate the methodology proposed in this research and com-pare well with the analytical and numerical solutions, experimental and field data.
The methodology proposed in this thesis provides a computational tool to study con-fined viscoplastic flows, common in industry, and debris viscoplastic flows with free surface.El objetivo de esta tesis es formular y evaluar una metodología para la resolución de las ecuaciones de Navier-Stokes para los fluidos viscoplásticos de Bingham y de Herschel-Bulkley mediante el método de los elementos finitos mixtos estabilizados velocidad/presión. Se desarrolla una formulación teórica, se realiza la implementación computacional y se presentan y evalúan soluciones numéricas para estos fluidos viscoplásticos. Los fluidos viscoplásticos se caracterizan por presentar una tensión de corte mínima, denominada tensión de fluencia. Por encima de esta tensión de corte mínima el fluido comienza a moverse. En caso de no superarse esta tensión de fluencia, el fluido se comporta como un cuerpo rígido o quasi-rígido, con velocidad de deformación nula. Se presentan inicialmente las ecuaciones de Navier-Stokes para un fluido y dos fluidos incompresibles e inmiscibles considerando superficie libre. Se presenta una revisión de los modelos reológicos Newtonianos y los modelos no-Newtonianos. Se hace una descripción detallada de los modelos viscoplásticos. Se describen los modelos viscoplásticos regularizados de Papanastasiou. Se proponen modelos regualarizados de doble viscosidad como alternativa a los comúnmente usados. Se deducen las soluciones analítica en flujos paralelos para el fluido Newtoniano, el fluido de Bingham, de Herschel-Bulkley, el fluido pseudoplástico y dilatante. Se desarrolla el modelo discreto, así como la formulación estabilizada con los métodos de subescalas algebraica (Algebraic subgrid scale, ASGS), de subescalas ortogonales (Orthogonal subgrid scale, OSS) y de subescalas ortogonales con la presión y el termino convectivo desacoplados, split-OSS. En el caso del fluido con superficie libre se presenta el método euleriano simplificado, el cual usa el método de superficie de nivel level set para resolver el movimiento de esta superficie libre. Se presenta un estudio de convergencia con los métodos de estabilización OSS y ASGS en los flujos paralelos de Bingham y de Herschel-Bulkley. Los modelos regularizados de doble viscosidad muestran menor error de convergencia que los usados regularmente. Se presentan las soluciones numéricas desarrolladas en esta tesis para un amplio conjunto de problemas benchmark. Pueden dividirse en tres grupos: flujos de Bingham, flujos de Herschel-Bulkley y flujos con superficie libre. Las soluciones obtenidas validan la metodología propuesta en este trabajo de investigación comparándose muy bien con las soluciones analíticas, numéricas, con resultados experimentales y datos de campo. La metodología propuesta en esta tesis proporciona una herramienta computacional para estudiar flujos viscoplásticos confinados, muy comunes en la industria, y los flujos detríticos viscoplásticos con superficie libre.
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May, Lea Lita. "The effects of recess on kindergarten student behavior /." Read thesis online, 2010. http://library.uco.edu/UCOthesis/MayLL2010.pdf.
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Gruber, Jakub. "Využití podnikových dat k zabezpečování kvality výrobku." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-442862.
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The task of the thesis is a theoretical analysis and description of the use of company data. Emphasis is placed on the system analysis of the problem. The specific production process and the data available from it are evaluated, which help to find a technical and economic evaluation.
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Botelho, Fabiana de Souza. "Efeito das gomas xantana e/ou guar na textura de pães isentos de glúten elaborados com farinhas de arroz e de milho." Master's thesis, ISA/UTL, 2012. http://hdl.handle.net/10400.5/5324.
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Mestrado em Ciências Gastronómicas - Instituto Superior de Agronomia / Faculdade de Ciências e Tecnologia. Universidade Nova de LisboaThe production of gluten-free bread poses a technological challenge that involves the creation of viscoelastic dough without the support of the gluten network (present on bread from wheat). For that purpose the, industry usually uses hydrocolloids. However the resulting bread is pricy and less accessible. The objective of this study is to adapt this technique to the home production of gluten-free bread. The effects of xanthan and guar gums in bread doughs, as well as in the final texture of such bread, were studied. Gluten free doughs were evaluated regarding their rheologic properties and texture parameters. Bread was evaluated in terms of texture and colour. Different gum proportions were studied in a total concentration of 1% (w/w). The proportion of 1:1 mixture originated a dough with an improved technological characteristic and a bread less firm than the control. For this proportion, a reduction of the total gum concentration to 0.5% was evaluated, resulting in an improvement of the characteristics of the bread. Previous hydration of gums was also evaluated (30 and 60 min) showing no significant effect on final bread characteristics. Aging curves showed that bread firmness significantly increases with time, but gums effects are sustained
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MacDougall, Audrey Anne [Verfasser], and Jochen [Akademischer Betreuer] Dahm-Daphi. "The Influence of Cadmium on the Repair of DNA Double-Strand Breaks / Audrey Anne MacDougall. Betreuer: Jochen Dahm-Daphi." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2014. http://d-nb.info/1057001732/34.
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Ponte, João André Moniz. "A cadeia de abastecimento da broa de milho em Portugal e a aplicação das leis de coexistência." Master's thesis, ISA, 2014. http://hdl.handle.net/10400.5/6981.
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Mestrado em Engenharia Agronómica - Instituto Superior de AgronomiaThis paper/study has been carried out within the scope of the PRICE Project (Practical Implementation of Coexistence in Europe) and seeks to line out a pattern or characterization of the supply chain for maize bread in Portugal as well as to verify the good segregation between the two types of maize. Surveys were held aiming producers, storers, retailers and wholesalers, and mills that work with yellow maize and white maize, but also bakeries that have an output of yellow or white maize bread. Questionnaires were carried out mostly in the Districts of Viana do Castelo, Braga, Porto, Coimbra and Leiria during the months of July / August 2013 and December 2013 / January 2014. It was established that the risk of adventitious presence on GM maize is real and thus there is the possibility of maize bread being traded with percentages of GMO’s exceeding (in excess of) 0.9% without being labelled. A lot of shortcomings in the traceability of maize batches along the supply chain were detected. Only a minority of firms have screening tests for the presence of GMO’s performed and many a time there is no appropriate documentation / certification regarding the presence of GMO’s which should accompany the maize batches.
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CAVALCANTI, Mônica Tejo. "Utilização das sementes da faveleira (Cnidoscolus phyllacanthus (Mart.) Pax et K. Hoffm. ) em produtos alimentícios." Universidade Federal de Campina Grande, 2011. http://dspace.sti.ufcg.edu.br:8080/jspui/handle/riufcg/1812.
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A faveleira (Cnidosculus phyllacanthus Pax. et K. Hoffm.) é uma Euforbiácea que possui amêndoas com grande potencial para exploração, sendo rica em óleos e proteínas alimentares, é encontrada em todos os estados do Nordeste Brasileiro até o norte de Minas Gerais, principalmente na região do semi-árido. Objetivando a sua aplicação como uma alternativa para a alimentação humana, nesse trabalho foi estudado o uso das sementes da faveleira em formulados alimentícios (pão de forma e bebida láctea fermentada) visando melhorar suas características funcionais. As sementes da faveleira apresentaram amêndoas com peso de 55,85% do peso total da semente. As farinhas das sementes e das amêndoas apresentaram elevado conteúdo de lipídio (22,10 e 40,96%) e de proteína (26,25 e 35,52%) e depois de desengordurada, a farinha das amêndoas apresentou 56,18% de proteínas com presença de todos os aminoácidos essenciais, sendo a leucina o aminoácido essencial com maior concentração por grama de proteína (34,35 mg de aminoácido/g de proteína). O isolado protéico obtido apresentou coloração amarelo claro e inodoro, sendo 85,42% das proteínas extraídas. Quando aplicada como ingrediente em pão de forma, a farinha da faveleira e o seu isolado protéico proporcionaram um produto com maior teor de proteínas, variando entre os experimentos de 9,96 a 11,02% e de lipídios, variando de 2,36 a 5,80%, sendo dependentes da concentração da farinha das amêndoas da faveleira. Os pães elaborados não diferenciaram sensorialmente do pão padrão, isto indica que o produto não variou o seu aspecto gera. As sementes da faveleira foram maceradas em diferentes condições a fim de se obter o extrato solúvel e o experimento que obteve maior absorção de água pelas sementes foi com solução de bicarbonato de sódio a 0,5% a temperatura de 60ºC, uma vez que no final de 6 horas de maceração, as sementes passaram de 6,30 para 33,85% de umidade. O extrato apresentou 2,61% de proteínas, 2,01% de lipídios e pH de 6,23. A bebida láctea enriquecida com o extrato solúvel das sementes da faveleira apresentou visualmente coloração branco-amarelada, com textura e odor característicos deste tipo de produto, porém sobressaindo um aroma amendoado. Em 6 horas de fermentação a formulação com 20% do extrato da faveleira e 7,5% de inóculo contendo os micro-organismos Streptococcus termophilus e Lactobacillus delbruekii bulgaricus observou-se acidez de 74,67 °D, pH de 4,31 e 0,11 g de biomassa. A bebida láctea elaborada teve teor de umidade de 82,77%, 0,65% de cinzas, 0,01% de lipídios diferindo estatisticamente da bebida láctea padrão com 84,15% de umidade, 0,50% de cinzas e 1,74% de lipídios. Na bebida láctea adicionada do extrato das sementes da faveleira obtém-se melhor produto visual, melhor plasticidade, homogeneidade, textura, com formulação base de menor custo, melhor qualidade nutricional e ainda sem a adição de aditivo. As sementes da faveleira apresentam potencial para uso em formulados alimentícios, melhorando a sua qualidade nutricional e obtendo-se produtos com alegação funcional.
The “faveleira” (Cnidosculus phyllacanthus Pax. et K. Hoffm.) is a Euforbiácea that has almond like a food oils and proteins potencial exploration and it’s found in all the states of Brazilian Northeast even in the North of Minas Gerais, mainly in semi-arido regions. Having like a point of its application as a alternative to the human alimentation, in this paper has been studied its use in food formulation. (bread bun dairy fermented) with the point to improve its functional characteristics. The seeds of “faveleira” presented almond with weight of 55.85% of seed’s total weight. The almond float presented high content of lipids (22.10 to 40.96%) and of protein (26.5 to 35.52%), after defatted, the float presented 56.18% of proteins with the presence of all the essential aminoacids, being the leucin the essential aminoacid with the highest concentration per gram of protein (34.35 mg of aminoacids /g of protein). The protein isolated obtained presented 85.42% of soluble proteins with yellow color and odorless . When applied as ingredient on bread bun, the float of “faveleira” and its protein isolated gave into the product higher of protein and lipids quantity without differentiate sensorialy of the bread standard on the seven experiments analyzed. The seeds of “faveleira” were macerated in different conditions with the objective to obtain the soluble extract and the experiment that had higher water absorption through the seeds was the one with sodium bicarbonate 0.5% on the temperature of 60ºC, because about 6 hours of maceration, the seeds passed of 6.30 to 33.85% of humid. The extract presented presented 2.61% of proteins, 2.01% of lipids on pH of 6.23. A dairy fermented added with the soluble extract of seeds of “faveleira” presented visually coloration white-yellowed, with characteristic texture and smell sort of this product, however protruding an almonded flavor. About 6 hours of fermentation the formulation with 20% of the extract of “faveleira” and 7.5% of inoculus containing the microorganisms Streptococcus termophilus and Lactobacillus delbruekii bulgaricus presented acidity of 74.67 ºD, pH of 4.31 and 0.11g of biomass. The dairy fermented elaborated presented quantity of humid of 82.77%, 0.65% of grays, 0.01% of lipids differing statistically of the standard dairy fermented that presented 84.15% of humid, 0.50% of grays and 1.74% of lipids. In the dairy fermented added in the extract of seeds of “faveleira” the result’s a better visual product, better plasticity, homogenization, texture and with base formulation in low costs and better nutritional quality and even without no addictive addiction. The seeds of faveleira have potential for use in formulated food, improving the nutritional quality and obtaining products with functional claimming.
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Krause, Jakob. "Kontextsensitive Prognoseverfahren für das Abnutzungsverhalten von technischen Systemen." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-130908.
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Technische Systeme nutzen sich ab. Dadurch bedingt kommt es zu Ausfällen. Um die Funktionstüchtigkeit von abgenutzten technischen Systemen wiederherzustellen, werden Instandsetzungsmaßnahmen durchgeführt. Da die Folgen eines unerwartet eintretenden Ausfalls drastisch sein können, ist es sinnvoll, das Abnutzungsverhalten eines technischen Systems vorherzusagen und so den Zeitpunkt von Instandsetzungsmaßnahmen zielgerichtet zu planen. Die Erstellung von Abnutzungsprognosen wird dadurch erschwert, dass sich technische Systeme oft variabel, in Abhängigkeit von auf sie einwirkenden Beanspruchungen, abnutzen. Außerdem wird diese Abnutzungsvariabilität von betriebsbedingten Einflüssen überlagert, was deren Modellierung erschwert. Im Rahmen dieser Arbeit wurden deshalb Lösungsansätze entwickelt, die es ermöglichen, die Abnutzungsvariabilität eines technischen Systems in Abnutzungsprognosen zu integrieren und dabei betriebsbedingte Einflüsse zu berücksichtigen. Somit können Instandsetzungsmaßnahmen präziser geplant, Ressourcen geschont sowie Kosten reduziert werdenTechnical systems are prone to deterioration. This leads to negative consequences like break-downs. Maintenance actions are executed in order to transfer technical systems back into healthy states. If break downs occur suddenly, the consequences can be dramatic. Therefore, it is reasonable to schedule maintenance actions based on health-state predictions. Thereby, health state predictions are impeded by the fact that technical systems often deteriorate variably, depending on certain stress factors. Furthermore, the effects of variable deterioration behavior can be hidden by system specific behavior. Thus, approaches are shown which integrate variable deterioration behavior into healthstate predictions while influences caused by the system specific behavior are considered. Consequently, maintenance actions can be scheduled more efficiently which spares resources and reduces costs
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Matuda, Tatiana Guinoza. "Estudo do congelamento da massa de pão: determinação experimental das propriedades termofísicas e desempenho de panificação." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/3/3137/tde-17112008-114317/.
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O conhecimento de propriedades termofísicas é importante na modelagem, na otimização e no projeto de equipamentos para processos como a fabricação de massa de pão congelada. Neste trabalho, as propriedades termofísicas condutividade térmica, difusividade térmica e calor específico foram determinadas experimentalmente ao longo do processo de congelamento da massa de pão, pois influenciam diretamente a cinética do processo que, por sua vez, determina a qualidade do pão produzido. Os resultados obtidos mostraram que algumas destas propriedades variaram em função do conteúdo inicial de água e principalmente devido à mudança da temperatura. O valor médio encontrado através da atividade de água das massas (aw = 0,950), para temperatura inicial de congelamento, pode explicar alguns desvios no ajuste dos dados experimentais a modelos disponíveis na literatura baseados na lei de Raoult, que são estritamente relacionados à fração de gelo formada. O uso combinado de goma guar e xantana reduziu a entalpia de fusão ao longo do tempo de armazenamento congelado (87,4 J.g-1 e 81,2 J.g-1 para a formulação sem gomas, não congelada e após 28 dias de armazenamento congelado; 84,4 J.g-1 e 76,9 J.g-1 para a formulação com 0,25% de goma guar e 0,25% de goma xantana na massa não congelada e após 28 dias de armazenamento congelado), indicando uma interação entre as gomas na capacidade de ligar água ao longo do tempo de congelamento. Porém, apesar do tempo de congelamento ter reduzido a entalpia de fusão, o processo de congelamento foi o principal fator na queda da taxa de fermentação e da produção de gás pelas leveduras independentemente do tempo de armazenamento congelado.The knowledge of thermophysical properties is important to model and optimize equipment design for frozen food processes. In this work, the thermophysical bread dough properties, such as, thermal conductivity, thermal diffusivity and specific heat were experimentally determined during freezing process, due to their influence on the kinetics process, and therefore on bread quality. The results showed that some properties varied according to the initial water content and mainly due to temperature changes. The average value of initial freezing temperature found by water activity (aw = 0.950) explains the deviations between experimental data and available models in the literature based on Raoults law, which is related to the ice mass fraction. The combined use of guar and xanthan gums reduced the fusion enthalpy along frozen storage time (87.4 J.g-1 and 81.2 J.g-1 for formulation without gum, non-frozen and after 28 frozen storage days; 84.4 J.g-1 and 76.9 J.g-1 for formulation with 0.25 % of guar gum and 0.25 % of xanthan gum in non-frozen and after 28 frozen storage days). It indicated the interaction between gums and their ability to hold water along frozen storage. Despite frozen storage reduced the fusion enthalpy, the freezing process itself was the main factor in the decrease in proofing rate and gas production by yeast cells.
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Carneiro, Samuel Ricardo Carvalho. "Caracterização mecânica e hidrogeológica dos maciços das cavas de Alegria Centro e Sul, Samarco Mineração S.A." Universidade Federal de Viçosa, 2013. http://locus.ufv.br/handle/123456789/3818.
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Previous issue date: 2013-08-01This paper presents a slope stability and groundwater flow analysis of rock masses of Alegria Centro and Alegria Sul pits, Samarco Mineração S.A., located in the Iron Quadrangle region, Minas Gerais State, Brazil. The main purpose was to characterize the mechanical properties - throughout GSI and RMR geomechanics classification methods, and hydrogeological characterization, of all rock and soil masses in the studied area, in order to produce data to support the preparation of a suitable pit design covering local particularities. This study included geological-geotechnical mapping, geotechnical drillhole logging, sampling of 45 undisturbed highly weathered block samples (classes V and VI) and drillhole core sampling. Physical and strength tests performed comprised geotechnical characterization tests, direct shear tests, uniaxial and triaxial strength tests and point load tests. To characterize the hydrogeological properties, in addition to the monitoring of groundwater level, field and laboratory experiments were carried out to determine the hydraulic conductivity and frequency fractures analyzes through the Cubic Law relation. In this study slope stability analyzes were performed by limit equilibrium and analyzes of flows by the finite element method, using the software SLIDE Rocscience Inc., with the determination of the critical safety factors before and after the drawdown.
Este trabalho apresenta uma avaliação da estabilidade e do fluxo subterrâneo dos maciços das cavas de expansão da Samarco Mineração S.A., denominadas Alegria Centro e Sul, localizadas na região do Quadrilátero Ferrífero, Minas Gerais, Brasil. O principal objetivo foi realizar uma caracterização das propriedades mecânicas para as quais combinaram-se os métodos de classificação geomecânica RMR e GSI, e hidrogeológicas, dos maciços rochosos e solos existentes na área de estudo, de maneira a produzir dados que permitissem a elaboração de um projeto de cava adequado à essas características. Este estudo contou com mapeamento geológico-geotécnico, descrição geotécnica de testemunhos de sondagens rotativas, amostragem de 45 blocos indeformados de rochas de alto grau de alteração (classes V e VI) e amostragem de testemunhos de furos de sondagens. Para caracterização das propriedades de resistência foram realizados ensaios de caracterização física, ensaios de cisalhamento direto, ensaios de compressão uniaxial e triaxial e ensaios de resistência à compressão puntiforme. Para caracterização das propriedades hidrogeológicas, além do monitoramento do nível d água subterrânea, foram conduzidos ensaios para determinação da condutividade hidráulica em campo, em laboratório e análises de frequência de fraturas através da relação conhecida como Lei Cúbica. No presente estudo foram realizadas análises de estabilidades por equilíbrio limite e análises de fluxos pelo método de elementos finitos, utilizando o software SLIDE da Rocscience Inc., com a determinação dos fatores de segurança críticos antes e após o rebaixamento do nível d água.
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Qiu, Ting-Yao, and 邱庭嶢. "Residue dam-Discharge Relationshipat Dam-Break Site." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/58290991031520792424.
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碩士淡江大學
水資源及環境工程學系碩士班
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This research applies model tests and numerical simulation to analyze, at dam failure, the relationship between flow rate and the residual dam body. The dam failure test model is located downstream of a linear channel with a bed slope S0 of 0.01, length of 12.00 m and width of 0.775 m. The shape of the breach is rectangular. The dam consists of three tiers, first of which is in the shape of the breach; the second tier is a horizontally symmetric double-door panels wider than the maximum width of the breach. A removable divider that can be pulled up makes the third tier. Removal of the divider separates it from the water body, which reduces the upward shear stress imposed by the divider on the water body. Simulation of a partial dam failure is done by setting the residual dam height to 0.250, 0.175, 0.125, 0.100, and 0.000 m tall and by modifying the residual dam body to make the breach width equal to 1.0, 0.9, 0.8 and 0.7 times of the channel width. This research also utilizes FLUENT simulation software with a three-dimensional model to generate a dam failure simulation under non-steady flow and turbulent flow modes. The simulation criteria are the same as those of the physical model tests, and the simulation results are compared and analyzed with the physical test results.