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1
Saghebian, Seyed Mahdi, Kiyoumars Roushangar, V. S. Ozgur Kirca, and Roghayeh Ghasempour. "Modeling total resistance and form resistance of movable bed channels via experimental data and a kernel-based approach." Journal of Hydroinformatics 22, no. 3 (February 17, 2020): 528–40. http://dx.doi.org/10.2166/hydro.2020.094.
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Abstract An accurate prediction of roughness coefficient in alluvial channels is of substantial importance for river management. In this study, the total and form resistance in alluvial channels with dune bedform were assessed using experimental data. First, the data of experiments carried out at the Hydraulic Laboratory of University of Tabriz was used to investigate the impact of hydraulic and sediment parameters on roughness coefficient. Then, these data were combined with other laboratory data, and the total and bedform resistance were modeled via a Gaussian Process Regression (GPR) approach. For models, developing different input combinations were considered based on flow and sediment characteristics. The obtained results from the experiments showed that the Reynolds number has a better correlation with flow resistance in comparison with other hydraulic parameters. It was found that the roughness variations due to bedform are almost between 40 and 80% of the total roughness coefficient. Also, the obtained results proved the capability of the GPR method in the modeling process. It was found that the model which took the advantages of both flow and sediment characteristics performed better compared to the other models. The sensitivity analysis results showed that the Reynolds number has the most significant impact in the prediction process.
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Samma, Hamidreza, Amir Khosrojerdi, Masoumeh Rostam-Abadi, Mojtaba Mehraein, and Yovanni Cataño-Lopera. "Numerical simulation of scour and flow field over movable bed induced by a submerged wall jet." Journal of Hydroinformatics 22, no. 2 (January 30, 2020): 385–401. http://dx.doi.org/10.2166/hydro.2020.091.
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Abstract Dam construction continues its rapid expansion around the world primarily for the purpose of hydropower generation. One important consequence of such projects is local scour at the downstream of the dam caused by outflow of excess reservoir water through spillways or bottom outlets that is associated with high velocities. The scour development endangers the dam foundation and river banks and undermines the stability of the hydraulic structures. In this study, a detailed three-dimensional (3D) flow simulation is conducted to investigate the complex fluid–sediment interactions leading to the formation of the scour hole and ridge systems downstream of a near-bottom jet. Three different bed-load equations, including Meyer-Peter–Müller, Nielsen, and Van Rijn formulas, are applied for calculating the bed-load transport rate. Comparison with a series of available experimental data shows that the Meyer-Peter–Müller equation results in better predictions than the two other relations. The performance of different turbulence models to reproduce vertical profiles of velocity and scour characteristic against the experimental data were evaluated. The vertical and horizontal profiles of the scour hole-ridge system are also compared with the corresponding experimental ones. The numerical model satisfactorily reproduces the geometric parameters representing the scour hole. However, the model overestimates the length of the scour hole.
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Gaines, Roger A., and Stephen T. Maynord. "Microscale Loose-Bed Hydraulic Models." Journal of Hydraulic Engineering 127, no. 5 (May 2001): 335–38. http://dx.doi.org/10.1061/(asce)0733-9429(2001)127:5(335).
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Vasquez, Jose A., Robert G. Millar, and Peter M. Steffler. "Two-dimensional finite element river morphology model." Canadian Journal of Civil Engineering 34, no. 6 (June 1, 2007): 752–60. http://dx.doi.org/10.1139/l06-170.
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We report the development and application of a river morphology model based on the two-dimensional depth-averaged hydrodynamic model River2D. This new movable bed version of River2D was applied to simulate the bed elevation changes in four experiments: bed aggradation due to sediment overload, bed degradation by sediment supply shut-off, knickpoint migration, and bar formation in a variable-width channel. Some conditions in these experiments involved quick changes in the upstream boundary conditions, rapidly varied flow, supercritical flow, hydraulic jumps, and secondary flows. The results of the model agreed well with measured data. Notable features of the model are the use of a flexible unstructured mesh based on triangular finite elements to provide higher spatial resolution in areas of interest and transcritical flow capabilities to simulate supercritical flow and hydraulic jumps over movable beds. Key words: numerical modeling, rivers, scour, sedimentation, two-dimensional, finite elements.
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Cui, Xinzhuang, Jiong Zhang, Darhao Chen, Shucai Li, Qing Jin, Yingjie Zheng, and Sheqiang Cui. "Clogging of pervious concrete pile caused by soil piping: an approximate experimental study." Canadian Geotechnical Journal 55, no. 7 (July 2018): 999–1015. http://dx.doi.org/10.1139/cgj-2017-0238.
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Due to their high permeability and high strength, pervious concrete piles (PCPs) can improve ground bearing capacity. However, clogging of pervious concrete in practice is a potential disadvantage. To investigate the clogging mechanism of PCPs due to sand piping, a series of laboratory simulation tests is conducted on a developed hydraulic conductivity test system. This testing demonstrates the effects of pervious concrete porosity, grading of fine movable particles, mix ratio of skeleton particles to movable particles, relative density of soil, and distance between PCPs on PCP clogging. The experimental test results show that the hydraulic conductivity of PCP decreases for approximately 70 min and then becomes relatively stable. In addition, it is observed that PCP clogging rarely occurs in cases of low pervious concrete porosity, small movable sand particle size, high sand relative density, and large pile distance. The results also show that measurement of electrical conductivity can be an alternative method of hydraulic conductivity measurement. Based on the test results, preliminary clogging models are proposed.
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Guimarães, André, Carlos Coelho, Fernando Veloso-Gomes, and Paulo A. Silva. "3D Physical Modeling of an Artificial Beach Nourishment: Laboratory Procedures and Nourishment Performance." Journal of Marine Science and Engineering 9, no. 6 (June 3, 2021): 613. http://dx.doi.org/10.3390/jmse9060613.
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Beach nourishment represents a type of coastal defense intervention, keeping the beach as a natural coastal defense system. Altering the cross-shore profile geometry, due to the introduction of new sediments, induces a non-equilibrium situation regarding the local wave dynamics. This work aims to increase our knowledge concerning 3D movable bed physical modeling and beach nourishment impacts on the hydrodynamics, sediment transport, and morphodynamics. A set of experiments with an artificial beach nourishment movable bed model was prepared. Hydrodynamic, sediment transport, and morphological variations and impacts due to the presence of the nourishment were monitored with specific equipment. Special attention was given to the number and positioning of the monitoring equipment and the inherent constraints of 3D movable beds laboratory tests. The nourishment induced changes in the beach dynamics, leading to an increase in the flow velocities range and suspended sediment concentration, and effectively increasing the emerged beach width. Predicting and anticipating the morphological evolution of the modeled beach has a major impact on data accuracy, since it might influence the monitoring equipment’s correct position. Laboratory results and constraints were characterized to help better define future laboratory procedures and strategies for increasing movable bed models’ accuracy and performance.
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Foley, Patrick M., and Aaron W. Buesing. "Discussion of “Microscale Loose-Bed Hydraulic Models” by Stephen T. Maynord." Journal of Hydraulic Engineering 128, no. 10 (October 2002): 952. http://dx.doi.org/10.1061/(asce)0733-9429(2002)128:10(952).
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Maynord, Stephen T. "Closure to “Microscale Loose-Bed Hydraulic Models” by Stephen T. Maynord." Journal of Hydraulic Engineering 128, no. 10 (October 2002): 952. http://dx.doi.org/10.1061/(asce)0733-9429(2002)128:10(952.2).
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Xiao, B. J., and L. J. Qiu. "Steady state thermal-hydraulic models of pebble bed blankets on hybrid reactors." Fusion Engineering and Design 27 (March 1995): 253–57. http://dx.doi.org/10.1016/0920-3796(95)90135-3.
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Kenfaoui, M., and C. Marche. "Comment évaluer l'érosion d'une vallée sous l'écoulement de rupture d'un barrage." Canadian Journal of Civil Engineering 13, no. 4 (August 1, 1986): 474–84. http://dx.doi.org/10.1139/l86-071.
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This laboratory experimental study deals with dam-break flows on movable beds. It demonstrates significant differences between these wave parameters and values of the same parameters estimated on fixed beds. Moreover it is shown that under specific conditions some sediment transport models for steady flows can be applied to estimate bed erosion for this particular type of flow. Key words: dam, dam-break, break flows, erosion, laboratory tests.
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Hou, Jingming, Hao Han, Zhanbin Li, Kaihua Guo, and Yi Qin. "Effects of morphological change on fluvial flood patterns evaluated by a hydro-geomorphological model." Journal of Hydroinformatics 20, no. 3 (February 13, 2018): 633–44. http://dx.doi.org/10.2166/hydro.2018.142.
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Abstract High aggradation and degradation in a river induced by the last flood event will raise and decrease the risk of an upcoming flood event, respectively. To quantitatively investigate this effect, a two-dimensional (2D) hydrodynamic model coupled with a sediment transport the river-bed evolution models is developed. After being validated against two experimental benchmark tests, the model is applied to simulate the effects of the morphological change on flood patterns. It is found in two experimental scale tests that bed evolution may have substantial influence on water level, which is directly related to flood risk extent. In the application of the model computing a realistic flood event in Bayangaole Reach of Yellow River, the results show that the water surface level becomes lower for an upcoming flood event with the same hydrograph, indicating the flood risk considerably decreases in the next flood event. The effect of a perturbed bed therefore could be of significance for fluvial flood over a movable bed and therefore to flood risk management.
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Roushangar, Kiyoumars, and Saman Shahnazi. "Prediction of sediment transport rates in gravel-bed rivers using Gaussian process regression." Journal of Hydroinformatics 22, no. 2 (October 25, 2019): 249–62. http://dx.doi.org/10.2166/hydro.2019.077.
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Abstract Estimating sediment transport rate in rivers has high importance due to the difficulties and costs associated with its measurement, which has drawn the attention of experts in water engineering. In this study, Gaussian process regression (GPR) is applied to predict the sediment transport rate for 19 gravel-bed rivers in the United States. To compare the performance of GPR, the support vector machine (SVM) as a common type of kernel-based models was developed. Model inputs of sediment transport were prepared based on two scenarios: the first scenario considers only hydraulic characteristics and the second scenario was formed using hydraulic and sediment properties. Obtained results revealed that the GPR models present better performance compared to the SVM models and other empirical sediment transport formulas. Also, it was found that incorporating the second scenario as input led to better predictions. In addition, performing sensitivity analysis showed that the ratio of average velocity to shear flow velocity is the most effective parameter in predicting the sediment transport rate of gravel-bed rivers.
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Hui, Ji, Nie Song-Lin, and Bai Xiao-Rong. "Simulation on mechanism of contamination mitigation through Higee and hydrocyclone techniques in fluid power system." Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering 232, no. 1 (December 13, 2016): 77–93. http://dx.doi.org/10.1177/0954408916684161.
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In this study, an innovative Higee hydraulic oil purification device capable of removing the solid particle contaminants and water moisture simultaneously is developed for dealing with the contamination control problem of fluid power systems. The purification device is considered as a combination of two units (hydrocyclone separator and rotating packed bed) according to different separation functions. The mathematical models about the migration regularity and dynamic behavior of different phases have been established, in which discrete phase model model is employed to simulate the solid particles – hydraulic oil separation, and Eulerian model is selected as the multiphase simulation model to simulate the hydraulic oil – water moisture separation. Simulation results demonstrate that the hydrocyclone separator can remove solid particles of 5 to 15 µm, while the rotating packed bed can mitigate water moisture. The results indicate that the developed Higee hydraulic oil purification device can provide an effective and efficient manner for controlling the contamination level of fluid power systems.
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Minor, B., C. D. Rennie, and R. D. Townsend. ""Barbs" for river bend bank protection: application of a three-dimensional numerical model." Canadian Journal of Civil Engineering 34, no. 9 (September 1, 2007): 1087–95. http://dx.doi.org/10.1139/l07-088.
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A three-dimensional numerical model was used to examine the turbulent flow field and associated sediment transport due to a series of barbs (submerged groynes) in a channel bend. Model results were in good agreement with measured laboratory data and adequately simulated the important features of sediment transport. Statistical comparison of the predicted and measured equilibrium bed geometry found average regression coefficients of determination of 0.77 and 0.72 for the 90° and 135° channels, respectively. The predicted velocity data followed expected trends. The capability of a three-dimensional numerical model to simulate sediment transport through bend sections of a channel containing barbs was verified. This included the simulation of the effects of different arrangements of barb groups and an analysis of the data to determine the relation of the flow field to associated scour and deposition in a complex fluvial environment. These novel results are useful for improved analyses of the bank-protection capabilities of these structures and for the development and improvement of design guidelines.Key words: three-dimensional models, numerical models, movable bed models, channel bends, turbulence, secondary flow, scour, barbs, groynes.
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Ahmadi, Sayed Masihullah, Yoshimichi Yamamoto, and Vu Thanh Ca. "Rational Evaluation Methods of Topographical Change and Building Destruction in the Inundation Area by a Huge Tsunami." Journal of Marine Science and Engineering 8, no. 10 (October 7, 2020): 762. http://dx.doi.org/10.3390/jmse8100762.
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In the case of huge tsunamis, such as the 2004 Great Indian Ocean Tsunami and 2011 Great East Japan Tsunami, the damage caused by ground scour is serious. Therefore, it is important to improve prediction models for the topographical change of huge tsunamis. For general models that predict topographical change, the flow velocity distribution of a flood region is calculated by a numerical model based on a nonlinear long wave theory, and the distribution of bed-load rates is calculated using this velocity distribution and an equation for evaluating bed-load rates. This bed-load rate equation usually has a coefficient that can be decided using verification simulations. For the purpose, Ribberink’s formula has high reproducibility within an oscillating flow and was chosen by the authors. Ribberink’s formula needs a bed-load transport coefficient that requires sufficient verification simulations, as it consumes plenty of time and money to decide its value. Therefore, the authors generated diagrams that can define the suitable bed-load coefficient simply using the data acquired from hydraulic experiments on a movable bed. Subsequently, for the verification purpose of the model, the authors performed reproduced simulations of topography changes caused by the 2011 Great East Japan Tsunami at some coasts in Northern Japan using suitable coefficients acquired from the generated diagrams. The results of the simulations were in an acceptable range. The authors presented the preliminary generated diagrams of the same methodology but with insubstantial experimental data at the time at the International Society of Offshore and Polar Engineers (ISOPE), (2018 and 2019). However, in this paper, an adequate amount of data was added to the developed diagrams based on many hydraulic experiments to further raise their reliability and their application extent. Furthermore, by reproducing the tsunami simulation on the Sendai Natori coast of Japan, the authors determined that the impact of total bed-load transport was much bigger than that of suspension loads. Besides, the simulation outputs revealed that the mitigation effect of the cemented sand and gravel (CSG) banks and artificial refuge hills reduced tsunami damage on Japan’s Hamamatsu coast. Since a lot of buildings and structures in the inundation area can be destroyed by tsunamis, building destruction design was presented in this paper through an economy and simplified state. Using the proposed tsunami simulation model, we acquired the inundation depth at any specific time and location within the inundated area. Because the inundation breadth due to a huge tsunami can extend kilometers toward the inland area, the evaluation of building destruction is an important measure to consider. Therefore, the authors in this paper presented useful threshold diagrams to evaluate building destruction with an easy and cost-efficient state. The threshold diagrams of “width of a pillar” for buildings or “width of concrete block walls” not breaking to each inundation height were developed using the data of damages due to the 2011 Great East Japan Tsunami.
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Rowan, Thomas, and Mohammed Seaid. "Efficient computational models for shallow water flows over multilayer erodible beds." Engineering Computations 37, no. 2 (August 23, 2019): 401–29. http://dx.doi.org/10.1108/ec-10-2018-0470.
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Purpose The purpose of this paper is to present a new numerical model for shallow water flows over heterogeneous sedimentary layers. It is already several years since the single-layered models have been used to model shallow water flows over erodible beds. Although such models present a real opportunity for shallow water flows over movable beds, this paper is the first to propose a multilayered solver for this class of flow problems. Design/methodology/approach Multilayered beds formed with different erodible soils are considered in this study. The governing equations consist of the well-established shallow water equations for the flow, a transport equation for the suspended sediments, an Exner-type equation for the bed load and a set of empirical equations for erosion and deposition terms. For the numerical solution of the coupled system, the authors consider a non-homogeneous Riemann solver equipped with interface-tracking tools to resolve discontinuous soil properties in the multilayered bed. The solver consists of a predictor stage for the discretization of gradient terms and a corrector stage for the treatment of source terms. Findings This paper reveals that modeling shallow water flows over multilayered sedimentary topography can be achieved by using a coupled system of partial differential equations governing sediment transport. The obtained results demonstrate that the proposed numerical model preserves the conservation property, and it provides accurate results, avoiding numerical oscillations and numerical dissipation in the approximated solutions. Originality/value A novel implementation of sediment handling is presented where both averaged and separate values for sediment species are used to ensure speed and precision in the simulations.
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Willis, David H., and B. G. Krishnappan. "Numerical modelling of cohesive sediment transport in rivers." Canadian Journal of Civil Engineering 31, no. 5 (October 1, 2004): 749–58. http://dx.doi.org/10.1139/l04-043.
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Techniques available to practicing civil engineers for numerically modelling cohesive mud in rivers and estuaries are reviewed. Coupled models, treating water and sediment as a single process, remain research tools but are usually not three-dimensional. The decoupled approach, which separates water and sediment computations at each model time step, allows the three-dimensional representation of at least the bed and the use of well-proven, commercial, numerical, hydrodynamic models. Most hydrodynamic models compute sediment transport in suspension but may require modification of the dispersion coefficients to account for the presence of sediment. The sediment model deals with the sediment exchange between the water column and the bed using existing equations for erosion and deposition. Both equations relate the sediment exchange rates to the shear stress in the bottom boundary layer. In real rivers and estuaries, a depositional bed layer is associated with a period of low flow and shear, at slack tide for example, whereas in numerical models a layer is defined by the model time step. The sediment model keeps track of the uppermost layers at each model grid point, including consolidation and strengthening. Although numerical hydrodynamic models are based strongly on physics, sediment models are only numerical frameworks for interpolating and extrapolating full-scale field or laboratory measurements of "hydraulic sediment parameters," such as threshold shear stresses. Calibration and verification of models against measurement are therefore of prime importance.Key words: cohesive sediment, mathematical modelling, settling velocity, erosion, resuspension, deposition, fluid mud, bed layers.
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Al-Fatlawi, Thair, Nassrin Al-Mansori, and Nariman Othman. "Laboratory study of stilling basin using trapezoidal bed elements." Przegląd Naukowy Inżynieria i Kształtowanie Środowiska 29, no. 4 (December 26, 2020): 409–20. http://dx.doi.org/10.22630/pniks.2020.29.4.35.
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When designing dam spillway structures, the most significant consideration is the energy dissipation arrangements. Different varieties of baffle blocks and stilling basins have been used in this context. However, the hydraulic jump form of stilling basin is considered to be the most suitable. The main objective of this research was to introduce four different baffle block shapes (models arranged from A to D, installed at slopes 0.00, 0.04, 0.06 and 0.08 in the stilling basins). To illustrate the consequences for the qualities of pressure-driven bounce, each model was attempted in the bowl. The trials applied Froude numbers between 6.5 and 9.2. The puzzle square model D provided the best outcomes compared to the models A, B, C and smooth. Model D with different models at inclines 0.00, 0.04, 0.06 and 0.08 was used to consider the impacts of perplex hinders on water driven-bounce when bed slants were changed. When the model D baffle used instead of a smooth bed at 0.08 slope, the reduction in y2 / y1 reached 12.8%, and Lj / y1 was 18.9%. Among the different bed slopes, a normal decrease in y2 / y1 ranged from approximately 10.3%, whereas the normal decrease in Lj / y1 was about 13.8% when the model D baffle was used instead of the model A baffle with a horizontal slope bed of 0.00. The results show that the new shapes led to a decrease in sequent profundity proportion and length of jump proportion; however, the energy dissipation proportion increased.
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Safari, Mir Jafar Sadegh. "Decision tree (DT), generalized regression neural network (GR) and multivariate adaptive regression splines (MARS) models for sediment transport in sewer pipes." Water Science and Technology 79, no. 6 (March 15, 2019): 1113–22. http://dx.doi.org/10.2166/wst.2019.106.
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Abstract Sediment deposition in sewers and urban drainage systems has great effect on the hydraulic capacity of the channel. In this respect, the self-cleansing concept has been widely used for sewers and urban drainage systems design. This study investigates the bed load sediment transport in sewer pipes with particular reference to the non-deposition condition in clean bed channels. Four data sets available in the literature covering wide ranges of pipe size, sediment size and sediment volumetric concentration have been utilized through applying decision tree (DT), generalized regression neural network (GR) and multivariate adaptive regression splines (MARS) techniques for modeling. The developed models have been compared with conventional regression models available in the literature. The model performance indicators, showed that DT, GR and MARS models outperform conventional regression models. Result shows that GR and MARS models are comparable in terms of calculating particle Froude number and performing better than DT. It is concluded that conventional regression models generally overestimate particle Froude number for the non-deposition condition of sediment transport, while DT, GR and MARS outputs are close to their measured counterparts.
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Avramova, M., A. Velazquez-Lozada, and A. Rubin. "Comparative Analysis of CTF and Trace Thermal-Hydraulic Codes Using OECD/NRC PSBT Benchmark Void Distribution Database." Science and Technology of Nuclear Installations 2013 (2013): 1–12. http://dx.doi.org/10.1155/2013/725687.
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The international OECD/NRC PSBT benchmark has been established to provide a test bed for assessing the capabilities of thermal-hydraulic codes and to encourage advancement in the analysis of fluid flow in rod bundles. The benchmark was based on one of the most valuable databases identified for the thermal-hydraulics modeling developed by NUPEC, Japan. The database includes void fraction and departure from nucleate boiling measurements in a representative PWR fuel assembly. On behalf of the benchmark team, PSU in collaboration with US NRC has performed supporting calculations using the PSU in-house advanced thermal-hydraulic subchannel code CTF and the US NRC system code TRACE. CTF is a version of COBRA-TF whose models have been continuously improved and validated by the RDFMG group at PSU. TRACE is a reactor systems code developed by US NRC to analyze transient and steady-state thermal-hydraulic behavior in LWRs and it has been designed to perform best-estimate analyses of LOCA, operational transients, and other accident scenarios in PWRs and BWRs. The paper presents CTF and TRACE models for the PSBT void distribution exercises. Code-to-code and code-to-data comparisons are provided along with a discussion of the void generation and void distribution models available in the two codes.
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Asheghi, Reza, Seyed Abbas Hosseini, Mojtaba Saneie, and Abbas Abbaszadeh Shahri. "Updating the neural network sediment load models using different sensitivity analysis methods: a regional application." Journal of Hydroinformatics 22, no. 3 (March 2, 2020): 562–77. http://dx.doi.org/10.2166/hydro.2020.098.
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Abstract The amount of transported sediment load by streams is a vital but high nonlinear dynamic process in water resources management. In the current paper, two optimum predictive models subjected to artificial neural network (ANN) were developed. The employed inputs were then prioritized using diverse sensitivity analysis (SA) methods to address new updated but more efficient ANN structures. The models were found through the 263 processed datasets of three rivers in Idaho, USA using nine different measured flow and sediment variables (e.g., channel geometry, geomorphology, hydraulic) for a period of 11 years. The used parameters were selected based on the prior knowledge of the conventional analyses in which the effect of suspended load on bed load was also investigated. Analyzed accuracy performances using different criteria exhibited improved predictability in updated models which can lead to an advanced understanding of used parameters. Despite different SA methods being employed in evaluating model parameters, almost similar results were observed and then verified using relevant sensitivity indices. It was demonstrated that the ranked parameters using SA due to covering more uncertainties can be more reliable. Evaluated models using sensitivity indices showed that contribution of suspended load on predicted bed load is not significant.
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Gyr and, Albert, and Wolfgang Kinzelbach. "Bed forms in turbulent channel flow." Applied Mechanics Reviews 57, no. 1 (January 1, 2004): 77–93. http://dx.doi.org/10.1115/1.1584063.
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Bed forms in channels result from the interaction between sediment transport, turbulence and gravitational settling. They document mechanisms of self-organization between flow structures and the developing structure of the bed. It is shown that these mechanisms can be characterized by length scales of the sediment, the bed form and the flow structure. Three types of interaction can be distinguished: 1) The first type of mechanisms can be observed at beds of sediment with grain diameter smaller than the typical structural dimension of turbulence. It is shown how with increasing hydraulic loading of the bed a hydraulically smooth surface develops structures, which turn from “orange peel” to stripe and arrowhead patterns and finally into ripples. This group of bed forms is limited to a grain diameter of d+=12.5 in viscous units. In the regime of the stripe structures drag reduction occurs. 2) If grains or bed forms reach a height, which leads to separation, a completely different regime prevails, which is determined by the self-organization of separation zones. A prominent example for these bed forms are dunes. 3) Demixing processes, secondary flows and roughness contrasts finally lead to the development of longitudinal and transverse banks. All three mechanisms are explained on the basis of kinematic models and documented by experimental data. Emphasis is put on the two-dimensionalization of bed forms in a highly 3-dimensional (3D) turbulent flow, which is traced back to the self organization of vortex systems. This review article contains 55 references.
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Jahadi, Mahsa, Hossein Afzalimehr, and Paweł M. Rowinski. "Flow structure within a vegetation patch in a gravel-bed river." Journal of Hydrology and Hydromechanics 67, no. 2 (June 1, 2019): 154–62. http://dx.doi.org/10.2478/johh-2019-0001.
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Abstract Investigation of the interactions between submerged vegetation patch and flow structure is of crucial importance for river engineering. Most of hydraulic models have been presented for fully developed flows over uniform vegetation in the laboratory conditions; however, the mentioned interactions are complex in river flows where the flow is not developed along small patch. This reveals a gap between developed and non-developed flow along the vegetation patch. This study was conducted in a gravel-bed river in the central Iran. The results reveal that the flow structure in evolving flow (non-developed flow) along the patch resembles that in shallow mixing layer. Accordingly, a shallow mixing layer model and modified equations are combined to quantify evolving area along the patch. The evolving shallow mixing layer equations for the flow along a non-uniform vegetation patch reach a reasonable agreement with field data. However, the spreading coefficient of this model less than one was reported in literature, 0.06 and 0.12. In addition, the flow immediately downstream the vegetation patch behaves similar to a jet and is parameterized by two conventional models, conventional logarithmic law and mixing layer theory. These models present a reasonable agreement with the measured velocity profiles immediately downstream the patch.
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Khosronejad, Ali, and C. D. Rennie. "Three-dimensional numerical modeling of unconfined and confined wall-jet flow with two different turbulence models." Canadian Journal of Civil Engineering 37, no. 4 (April 2010): 576–87. http://dx.doi.org/10.1139/l09-172.
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Wall-jet flow is an important flow field in hydraulic engineering, and its applications include flow from the bottom outlet of dams and sluice gates. An in-house three-dimensional (3-D) finite-volume Reynolds-averaged-Navier-Stokes (RANS) numerical model predicts the hydrodynamic characteristics of wall jets with square and rectangular source geometry. Either the low-turbulence Reynolds number k–ω or the standard k–ε turbulence closure models are applied. The calculated results for velocity profile and bed shear stress in both longitudinal and vertical directions compare favourably with both the published experimental results and the FLUENT® finite volume model. The two closure models are compared with the k–ω model, displaying 4% greater average accuracy than the k–ε model. Finally, the influence of lateral confinement of the receiving channel on wall-jet hydrodynamics is investigated, with decreased longitudinal deceleration and decreased bed shear stress observed in a confined jet. This has important implications for sediment transport in the receiving channels downstream of sluice gates.
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Chi, Yanbing, Peiling Yang, Zixuan Ma, Haiying Wang, Yuxuan Liu, Bingbing Jiang, and Zongguang Hu. "The Study on Internal Flow Characteristics of Disc Filter under Different Working Condition." Applied Sciences 11, no. 16 (August 22, 2021): 7715. http://dx.doi.org/10.3390/app11167715.
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A disc filter (DF) is an important component in a micro irrigation system. However, it has a high head loss and low filtration efficiency, which can lead to the inoperability of micro irrigation systems. To improve the filtration ability and to decrease the pressure loss of the irrigation system, it is necessary to internalize the hydraulic characteristics of DFs. In this study, the filter bed of a DF was divided into three parts, i.e., upper, middle, and lower, which were wrapped with a transparent film. The wrapped part was completely blocked. The purpose was to analyze the hydraulic characteristics of different clogged conditions in three types of filters under four types of flows. In addition, we attempted to simulate the filter operation process with computational fluid dynamics, based on two aspects—a macroscopic model and a simplified model. The results showed that the patterns of head loss among all of the DFs was consistent, and the macroscopic model that treated filter bed as a porous medium could express the measured results. The macroscopic models observed that there was a circular flow in the DF, and the flow velocity presented a symmetrical distribution in a horizontal direction. The middle of the filter element appeared in a high-pressure area and demonstrated the highest head loss, which may be the main flow area of the DF, and the inner flow characteristics of the DF were consistent under different conditions. The simplified models showed that the main flow area is near the filter bed in the inner DF, and the flow is tangent to the filter bed between 45 and 90 degrees in a horizontal direction. The uneven distribution of velocity and pressure on the filter bed might be necessary factors to impact filter efficiency.
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Smaga, Agnieszka. "Analysis of Prognosis of Lowland River Bed Erosion Based on Geotechnical Parameters." Studia Geotechnica et Mechanica 37, no. 4 (December 1, 2015): 57–63. http://dx.doi.org/10.1515/sgem-2015-0045.
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Abstract The river erosion is a complex process, the dynamics of which is very difficult to predict. Its intensity largely depends on hydraulic conditions of the river channel. However, it is also thought that natural resistance of the subsoil has a great influence on the scale of the erosion process. Predicting the effects of this process is extremely important in the case of constructing a piling structure (for example, artificial reservoirs). The partition of the river channel causes significant lowering of the river channel bed downstream the dam which threatens the stability of hydro technical and engineering (bridges) buildings. To stop this unwanted phenomenon, stabilizing thresholds are built. However, random location of thresholds significantly reduces their effectiveness. Therefore, taking under consideration natural geotechnical conditions of the subsoil appears to be extremely important. In the light of the current development of in-situ tests in geotechnics, an attempt to use results from these tests to predict the bed erosion rate was made. The analysis includes results from CPTU and DPL tests, which were carried out in the Warta River valley downstream the Jeziorsko reservoir. In the paper, the general diagrams for the procedure of obtaining and processing the data are shown. As a result, the author presents two multidimensional bed erosion rate models built based on hydraulic data and results from CPTU or DPL tests. These models allow taking more effective actions, leading to the neutralization of the effects of the intensive bed erosion process.
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Hu, Xiaodong, Kan Wu, Xianzhi Song, Wei Yu, Lihua Zuo, Gensheng Li, and Zhonghou Shen. "Development of a New Mathematical Model To Quantitatively Evaluate Equilibrium Height of Proppant Bed in Hydraulic Fractures for Slickwater Treatment." SPE Journal 23, no. 06 (August 23, 2018): 2158–74. http://dx.doi.org/10.2118/191360-pa.
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Summary The proppant bed develops and its height grows until it reaches the critical velocity and equilibrium height. This paper proposes a comprehensive mathematical model to evaluate the equilibrium height for slickwater treatment. We use well-accepted published experimental data and models from other groups to validate our model. After that, we investigate the effects of proppant properties and fluid properties on the equilibrium height. This work can provide critical insights to optimize the design of proppant parameters in a hydraulic fracture. Meanwhile, this model can be incorporated into fracture-propagation simulators for simulating proppant transport.
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Roushangar, Kiyoumars, and Roghayeh Ghasempour. "Evaluation of the impact of channel geometry and rough elements arrangement in hydraulic jump energy dissipation via SVM." Journal of Hydroinformatics 21, no. 1 (November 26, 2018): 92–103. http://dx.doi.org/10.2166/hydro.2018.028.
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Abstract Rough bed channels are one of the appurtenances used to dissipate the extra energy of the flow through hydraulic jump. The aim of this paper is to assess the effects of channel geometry and rough boundary conditions (i.e., rectangular, trapezoidal, and expanding channels with different rough elements) in predicting the hydraulic jump energy dissipation using support vector machine (SVM) as a meta-model approach. Using different experimental data series, different models were developed with and without considering dimensional analysis. The results approved capability of the SVM model in predicting the relative energy dissipation. It was found that the developed models for expanding channel with central sill performed more successfully and, for this case, superior performance was obtained for the model with parameters Fr1 and h1/B. Considering the rectangular and trapezoidal channels, the model with parameters Fr1, (h2−h1)/h1, W/Z led to better predictions. It was observed that between two types of strip and staggered rough elements, strip type led to more accurate results. The obtained results showed that the developed models for the case of simulation based on dimensional analysis yielded better predictions. The sensitivity analysis results showed that Froude number had the most significant impact on the modeling.
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Henry, Pierre-Yves, Jochen Aberle, Christy Ushanth Navaratnam, and Nils Ruther. "Hydraulic physical model production with Computer Numerically Controlled (CNC) manufacturing techniques." E3S Web of Conferences 40 (2018): 05065. http://dx.doi.org/10.1051/e3sconf/20184005065.
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Physical models are a well-accepted tool in hydraulic engineering, allowing for the detailed characterisation of flow processes and the validation of structure designs with complex boundary conditions. The methods used to construct physical models typically produce a surface roughness which does not necessarily scale with the surface roughness of the prototype. In this context, this paper discusses novel construction methods allowing a detailed reproduction of roughness elements in scaled models, such as Computer Numerically Controlled (CNC) manufacturing techniques and bed casting techniques. In particular, the present paper details the protocols developed to mill out a correct representation of the complex rock-fractured geometry of a closed channel which was obtained from Terrestrial Laser Scanners. The novelty of this scaled model production is the implementation of optical accesses in a closed (pressurized) hydraulic model, to allow for Particle Image Velocimetry measurements with a minimum impact on the reproduced roughness elements. The effectiveness of this production protocol is discussed in the context of modelling the roughness effects on the flow regime.
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Sun, Shiyan, Youjie Zhang, and Yanhua Zheng. "Research on Influence of Different Simulation Methods of Bypass Flow in Thermal Hydraulic Analysis on Temperature Distribution in HTR-10." Science and Technology of Nuclear Installations 2020 (June 26, 2020): 1–8. http://dx.doi.org/10.1155/2020/4754589.
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In pebble-bed high temperature gas-cooled reactor, gaps widely exist between graphite blocks and carbon bricks in the reactor core vessel. The bypass helium flowing through the gaps affects the flow distribution of the core and weakens the effective cooling of the core by helium, which in turn affects the temperature distribution and the safety features of the reactor. In this paper, the thermal hydraulic analysis models of HTR-10 with bypass flow channels simulated at different positions are designed based on the flow distribution scheme of the original core models and combined with the actual position of the core bypass flow. The results show that the bypass coolant flowing through the reflectors enhances the heat transfer of the nearby components efficiently. The temperature of the side reflectors and the carbon bricks is much lower with more side bypass coolant. The temperature distribution of the central region in the pebble bed is affected by the bypass flow positions slightly, while that of the peripheral area is affected significantly. The maximum temperature of the helium, the surface, and center of the fuel elements rises as the bypass flow ratio becomes larger, while the temperature difference between them almost keeps constant. When the flow ratio of each part keeps constant, the maximum temperature almost does not change with different bypass flow positions.
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Miedema, Sape A., and Robert C. Ramsdell. "The Limit Deposit Velocity model, a new approach." Journal of Hydrology and Hydromechanics 63, no. 4 (December 1, 2015): 273–86. http://dx.doi.org/10.1515/johh-2015-0034.
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Abstract In slurry transport of settling slurries in Newtonian fluids, it is often stated that one should apply a line speed above a critical velocity, because blow this critical velocity there is the danger of plugging the line. There are many definitions and names for this critical velocity. It is referred to as the velocity where a bed starts sliding or the velocity above which there is no stationary bed or sliding bed. Others use the velocity where the hydraulic gradient is at a minimum, because of the minimum energy consumption. Most models from literature are one term one equation models, based on the idea that the critical velocity can be explained that way. Here the following definition is used: The critical velocity is the line speed below which there may be either a stationary bed or a sliding bed, depending on the particle diameter and the pipe diameter, but above which no bed (stationary or sliding) exists, the Limit Deposit Velocity (LDV). The way of determining the LDV depends on the particle size, where 5 regions are distinguished. These regions for sand and gravel are roughly; very small particles up to 0.014–0.040 mm (d < δv), small particles from δv–0.2 mm, medium particles in a transition region from 0.2–2.00 mm, large particles > 2 mm and very large particles > 0.015·Dp. The lower limit of the LDV is the transition between a sliding bed and heterogeneous transport. The new model is partly based on physics and correlates well with experiments from literature.
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Roushangar, Kiyoumars, Mohammad Taghi Alami, Vahid Nourani, and Aida Nouri. "A cost model with several hydraulic constraints for optimizing in practice a trapezoidal cross section." Journal of Hydroinformatics 19, no. 3 (March 6, 2017): 456–68. http://dx.doi.org/10.2166/hydro.2017.081.
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Open channel structures are essential to infrastructure networks and expensive to manufacture. Optimizing the design of channel structures can reduce the total cost of a channel's length, including costs of lining, earthwork, and water lost through seepage and evaporation. The present research aims to present various optimization models towards the design of trapezoidal channel cross section. First, a general resistance equation was applied as a constraint. Next, a genetic algorithm (GA) was used to determine the optimal geometry of a trapezoidal channel section based on several parameters, i.e., depth, bottom width, and side slope. Eight different models were proposed and evaluated with no other constraint besides financial cost as well as with a normal depth, flow velocity, Froude number, top width, and by ignoring the cost of seepage. Numerical outcomes obtained by the GA are compared to previous studies in order to determine the most efficient model. Results from a single application indicate that the restriction of depth, velocity, and Froude number can increase the total cost, while restriction of the top width can decrease the cost of the construction. Also, the solution for various example problems incorporating different discharge values and bed slopes caused increase and decrease in cost, respectively.
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Koncsos, L., and G. Fonyó. "Analysis of the transport of cyanide spill on the Tisza River." Water Science and Technology 50, no. 5 (September 1, 2004): 101–7. http://dx.doi.org/10.2166/wst.2004.0315.
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The present paper deals with the wastewater pond accident in Nagybánya (Romania) in 2000 of which the result was an about 100 tons of highly toxic cyanide spill into the River Tisza. Measurements and laboratory tests were performed during the toxic wave transport. On the basis of this data set mass balance calculations were performed by hydraulic and transport models to investigate and better understand the effect of the accident and to calculate the possible heavy metal sedimentation process in Tisza River bed. This paper deals with calculations for cyanide and copper which are mostly associated to cyanide pollution.
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Mutel, Cornelia F. "From Wind to Water." Mechanical Engineering 122, no. 01 (January 1, 2000): 44–47. http://dx.doi.org/10.1115/1.2000-jan-1.
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A small-scale physical model of a hydropower turbine and its water flow is under study at the University of Iowa’s Institute of Hydraulic Research. The Institute of Hydraulic Research at the University of Iowa has developed a numerical code that accurately predicts the three-dimensional flow of water over the variable bed of a dam’s forebay and into a hydropower plant’s intakes. In addition, fisheries biologists working independently have identified basic behavioral patterns of salmonids. Once computational fluid dynamics models that merge water’s flow with fish behavior patterns are perfected, the effects of flow characteristics at countless points can be measured rapidly and economically, and design decisions can be made accordingly. The code thus promises to become a formidable planning tool that will save power utilities major amounts of both time and money. The codes eventually will allow the results of minute changes in hull or propeller structure to be realized with a few keyboard strokes. Iowa researchers are investigating the flow of moisture through the air as well as over land and through the sea.
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Reis, Guilherme da Cruz dos, Tatiane Souza Rodrigues Pereira, Geovanne Silva Faria, and Klebber Teodomiro Martins Formiga. "Analysis of the Uncertainty in Estimates of Manning’s Roughness Coefficient and Bed Slope Using GLUE and DREAM." Water 12, no. 11 (November 21, 2020): 3270. http://dx.doi.org/10.3390/w12113270.
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River discharge data are critical to elaborating on engineering projects and water resources management. Discharge data must be precise and collected with good temporal resolution. To elaborate on a more accurate database, this paper aims to quantify the uncertainty generated while applying Bayesian inference through the GLUE and DREAM methods. Both methods were used to estimate hydraulic parameters and compare between them with Manning’s equation. Throughout the statistical analysis, the uncertainties in the application of the models are used to determine the parameters of Manning’s roughness coefficient and bed slope. The validation was made via a comparison of the calculated maximum and minimum discharges, and the observed flow available at HidroWeb. In conclusion, both methods estimated the hydraulic parameters well, but a higher relative deviation was seen in the intervals with smaller calculated discharges; DREAM appears to be more accurate than GLUE, once the relative deviation in GLUE became greater.
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Ye, Chen, Wang Kelin, Sun Xiaofeng, Qu Jingyu, and Cao lihu. "Simulation on Incipient Particle Motion in Highly-Inclined Annulus." Recent Patents on Engineering 14, no. 1 (June 21, 2020): 103–12. http://dx.doi.org/10.2174/1872212113666190329234115.
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Background: Highly-inclined and horizontal wells have been widely used for the development of mature oilfield, marine oilfield, and low permeable oilfield. During drilling operations, cutting particles will accumulate in the low side of wellbore and cuttings bed may be formed, which may lead to high drag and torque, stuck pipe, and other drilling problems. We reviewed the patents about cutting bed cleaning tool. Objective: The goal of this work is to determine the incipient motion velocity or rate to re-suspend and remove the cutting particles. Methods: In this study, the random distribution function of particles is introduced to determine the percentage of incipient particle motion, and the mechanical models for rolling and lifting method considering the net gravity, drag force, lift force, additional mass force, adhesive force and flow pressure gradient force are developed to predict the incipient motion velocity or rate. Also, the model has been verified by published experimental data. Results: The critical particle size of incipient motion rate is approximately 1 mm. The incipient motion rate decreases as the height of cuttings bed decreases, and the minimum flow rate that prevents the bed formation may be estimated when bed height is small enough. Also, increasing wellbore inclination or fluid density has a positive effect on incipient motion rate, but increasing particle density or percentage of incipient particle motion has an adverse effect. Conclusion: This study may provide a guideline for designing hydraulic parameters and sand washing in the highly-inclined and horizontal wells, thereby contributingin economic production.
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Karolinczak, Beata, and Wojciech Dąbrowski. "Effectiveness of septage pre-treatment in vertical flow constructed wetlands." Water Science and Technology 76, no. 9 (July 20, 2017): 2544–53. http://dx.doi.org/10.2166/wst.2017.398.
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Abstract Septage is wastewater stored temporarily in cesspools. A periodic supply of its significant quantities to small municipal wastewater treatment plants (WWTPs) may cause many operational problems. In the frame of the research, it has been proposed to utilize vertical flow constructed wetlands for pre-treatment of septage prior to its input to the biological stage of a WWTP. The aim of the work was to assess the effectiveness of pre-treatment in relation to factors such as: seasonality, hydraulic load, pollutants load of the VF bed and interactions between these factors. The results proved that application of a VF bed to septage pre-treatment can significantly reduce the concentration of pollutants (biochemical oxygen demand (BOD5): 82%, chemical oxygen demand (COD): 82%, total suspended solids (TSS): 91%, total nitrogen (TN): 47%, ammonia nitrogen (NH4-N): 70%), and thus decrease the loading of the biological stage of a WWTP. The mathematical models of mass removal process were created. They indicate that in case of all analysed parameters, removed load goes up with the increase of load in the influent. However, with the increase of hydraulic load, a decrease of the removed BOD5, COD, TSS and total phosphorus, and in vegetation period an increase of TN, can be observed in terms of load. There are no statistically significant effects of seasonality.
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Liao, Chung-Ta, Keh-Chia Yeh, Yin-Chi Lan, Ren-Kai Jhong, and Yafei Jia. "Improving the 2D Numerical Simulations on Local Scour Hole around Spur Dikes." Water 13, no. 11 (May 23, 2021): 1462. http://dx.doi.org/10.3390/w13111462.
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Local scour is a common threat to structures such as bridge piers, abutments, and dikes that are constructed on natural rivers. To reduce the risk of foundation failure, the understanding of local scour phenomenon around hydraulic structures is important. The well-predicted scour depth can be used as a reference for structural foundation design and river management. Numerical simulation is relatively efficient at studying these issues. Currently, two-dimensional (2D) mobile-bed models are widely used for river engineering. However, a common 2D model is inadequate for solving the three-dimensional (3D) flow field and local scour phenomenon because of the depth-averaged hypothesis. This causes the predicted scour depth to often be underestimated. In this study, a repose angle formula and bed geometry adjustment mechanism are integrated into a 2D mobile-bed model to improve the numerical simulation of local scour holes around structures. Comparison of the calculated and measured bed variation data reveals that a numerical model involving the improvement technique can predict the geometry of a local scour hole around spur dikes with reasonable accuracy and reliability.
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Das, B. S., K. Devi, J. R. Khuntia, and K. K. Khatua. "Discharge estimation in converging and diverging compound open channels by using adaptive neuro-fuzzy inference system." Canadian Journal of Civil Engineering 47, no. 12 (December 2020): 1327–44. http://dx.doi.org/10.1139/cjce-2018-0038.
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The computation of total flow in a flooded river is very crucial work in designing economical flood defense schemes and drainage systems. Further, under non-uniform flow conditions like in converging and diverging compound channel, the traditional methods provide poor results with high errors. The analytical methods require the system of nonlinear equations to be solved, which is very complex. So, mathematical models that prompt in taking care of a complex system of problems are solved here through an artificial neural network (ANN) and adaptive neuro-fuzzy inference system (ANFIS). By utilizing ANN and ANFIS, an attempt is made to predict the discharge in converging and diverging compound channels. In the analysis, the most influencing dimensionless parameters such as friction factor ratio, area ratio, hydraulic radius ratio, bed slope, width ratio, relative flow depth, angle of converging or diverging, relative longitudinal distance, and flow aspect ratio are taken into consideration for computation of discharge. Gamma test and M-test have been performed to achieve the best combinations of input parameters and training length respectively. The significant input parameters that influence the discharge are found to be friction factor ratio, hydraulic radius ratio, relative flow depth, and bed slope. A suitable performance is achieved by the ANFIS model as compared to ANN model with a high coefficient of determination of 0.86 and low root mean square error of 0.005 in predicting the discharge of non-prismatic compound channels taken under consideration.
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Kanso, A., G. Chebbo, and B. Tassin. "Bayesian analysis for erosion modelling of sediments in combined sewer systems." Water Science and Technology 52, no. 5 (September 1, 2005): 135–42. http://dx.doi.org/10.2166/wst.2005.0126.
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Previous research has confirmed that the sediments at the bed of combined sewer systems are the main source of particulate and organic pollution during rain events contributing to combined sewer overflows. However, existing urban stormwater models utilize inappropriate sediment transport formulas initially developed from alluvial hydrodynamics. Recently, a model has been formulated and profoundly assessed based on laboratory experiments to simulate the erosion of sediments in sewer pipes taking into account the increase in strength with depth in the weak layer of deposits. In order to objectively evaluate this model, this paper presents a Bayesian analysis of the model using field data collected in sewer pipes in Paris under known hydraulic conditions. The test has been performed using a MCMC sampling method for calibration and uncertainty assessment. Results demonstrate the capacity of the model to reproduce erosion as a direct response to the increase in bed shear stress. This is due to the model description of the erosional strength in the deposits and to the shape of the measured bed shear stress. However, large uncertainties in some of the model parameters suggest that the model could be over-parameterised and necessitates a large amount of informative data for its calibration.
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Ashour, Mohamed A., Tarek Sayed, and Salah El-Attar. "Impact of curved shaped energy dissipaters downstream of head structures on both water energy dissipation and irrigation water quality." Limnological Review 15, no. 1 (March 1, 2015): 3–14. http://dx.doi.org/10.2478/limre-2015-0001.
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Abstract Using energy dissipaters on the soled aprons downstream of head structures is the main technique for accelerating hydraulic jump formation and dissipating a great amount of the residual harmful kinetic energy occurring downstream of head structures. In this paper, an experimental study was conducted to investigate some untested shapes of curved dissipaters with different angles of curvature and arrangements from two points of view. The first is to examine its efficiency in dissipating the kinetic water energy. The second is to examine the most effective shape and arrangement obtained from the aforementioned step in enriching the flow with dissolved oxygen for enhancement of the irrigation water quality. The study was held in the irrigation and hydraulic laboratory of the Civil Department, Faculty of Engineering, Assiut University, using a movable bed tilting channel 20 m long, 30 cm wide, and 50 cm high, using 21 types of curved dissipaters with different arrangements. A total of 660 runs were carried out. Results were analysed, tabulated and graphically presented, and new formulas were introduced to estimate the energy dissipation ratio, as well as the DO concentrations. Results in general showed that the dissipater performance is more tangible in dissipating the residual energy when the curvature is in the opposite direction to that of the flow. Also, the energy loss ratio increases with an increase in curvature angle (θ), until it reaches (θ = 120°), then it decreases again. The study also showed that using three rows of dissipaters give nearly the same effect as using four rows, concerning both the relative energy dissipation and dissolved oxygen content. So, it is recommended to use three rows of the curved dissipater with the angle of curvature (θ = 120°) in the opposite direction to that of the flow to obtain the maximum percentage of water energy dissipation downstream of head structures, and maximum dissolved oxygen content too
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Skipworth, Peter J., Simon J. Tait, and Adrian J. Saul. "Laboratory investigations into cohesive sediment transport in pipes." Water Science and Technology 33, no. 9 (April 1, 1996): 187–93. http://dx.doi.org/10.2166/wst.1996.0208.
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In the UK many sewers are laid to shallow gradients and as a consequence, suffer from recurrent sediment deposition. The loss in conveyance due to these deposits may contribute to hydraulic overloading problems and the wash-out of in-sewer sediment deposits may result in a rain induced “foul flush” of pollution which may subsequently be discharged via a CSO to the receiving water course. This paper reports the results of a series of controlled experiments in the laboratory in an attempt to better understand the factors which influence the erosion of cohesive sediment beds. Apparatus, formerly used for fixed bed work, was modified to assess the erosion characteristics of movable beds. Samples were taken from the flow during computer generated hydrographs and these were later assessed for the concentration of suspended sediment using a spectrophotometer. Whilst other studies have been concerned with the erodability of different sediments, this study has been limited to one cohesive sediment type and has concentrated on two aspects of the relationship between the properties of the flow hydrograph and the erosion and transport of cohesive sediment beds. Specifically, the effect of the rate of increase of the rising limb of the hydrograph and of the ultimate flowrate on the pollutograph have been examined. This series of experiments has produced evidence that the measured suspended sediment transport rate of cohesive-like materials exposed to a variable flowrate, is dependent both on the values of the final flowrate and on the rate of the initial temporal change of the flowrate, and is not solely dependent on the “steady state” flow variables.
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Faraj, Samara Saad, Rasha Salah Alkizwini, and Maad F. Al Juboury. "Simulate permeable reactive barrier by using a COMSOL model and comparison with the Thomas, Yoon–Nelson and Clark models for CR dye remediation by composite adsorbent (sewage and waterworks sludge)." Water Science and Technology 82, no. 12 (October 16, 2020): 2902–19. http://dx.doi.org/10.2166/wst.2020.500.
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Abstract The remediation of Congo Red (CR) dye by the synthetic sorbent composited from sewage and waterworks sludge was studied in batch and continuous experiments. The continuous experiments studied the composite synthetic after mixing with composite synthetic sorbent filter (CSF) glass waste to increase the hydraulic conductivity of the permeable reactive barrier (PRB). The synthetic composite sorbent was characterised by the nitrogen adsorption–desorption tests, field emission-scanning electron microscopy and X-ray diffraction. For evaluating the batch tests, the variable conditions of initial concentration, solution pH, agitation time and agitation speed were studied. The synthetic sorbent showed a high ability to remove the CR from a contaminated water, with maximum sorbent uptake equal to 9,469.211 mg/g and composite adsorbent-filter CSF equal to 4,415.946 mg/g. Pseudo-second-order kinetic model and Langmuir isotherm model governed the adsorption process. The column tests showed the highest reactivity, with 50:50 weight ratios of the adsorbent to filter glass waste. The experiments were done with different concentrations of CR and different bed heights of CSF as the PRB for 90 days. There was a delay in the breakthrough time when decreasing the contaminant concentrations and when increasing the composite adsorbent-filter CSF bed height. The breakthrough curves were well represented by the COMSOL model.
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Ashour, Mohamed A., Tarek Sayed, and Salah El-Attar. "A new water energy dissipater for efficient energy dissipation and enriching the flow with dissolved oxygen content." Limnological Review 14, no. 1 (March 1, 2014): 3–11. http://dx.doi.org/10.2478/limre-2014-0001.
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Abstract One of the most important problems Egypt is facing nowadays is saving and controlling the limited available quantity of water and its quality for irrigation and other purposes. Such goals may be achieved through different types of diversion head structures across the river and in the entrance of other carrying canals. The construction of diversion head structures, which usually causes many technical problems, should have the objective of solving and overcoming to protect the structure from failure. The main problem occurs downstream. Such structures have the harmful effect of converting the potential energy gained in the upstream side to a kinetic energy in the downstream side. This energy must be dissipated shortly and safely as near as possible to the head structure to avoid its destructive effect. The hydraulic jump is the most effective tool for the dissipation of water energy, accelerating the forming of the hydraulic jump downstream such structures became essential for achieving our main goal. Using energy dissipaters on the soled apron in the downstream side of the structures was the main technique for accelerating the hydraulic jump formation and dissipating great amount of the residual harmful kinetic energy occurring downstream head structures. So early, many researchers investigated different types, shapes, and arrangements of such dissipaters to evaluate its efficiency in dissipating the water energy and accelerating the forming of the hydraulic jump. In fact, in our present study we will try to investigate some other shapes of energy dissipaters, which have not been studied enough, by evaluating its positive technical impact on: (i) percentage value of dissipating kinetic water energy; (ii) percentage value of increasing the dissolved oxygen (DO) content in the irrigation water, and improving its quality. The study is proposed to be held in the irrigation and hydraulic laboratory of the Civil department, Faculty of Engineering, Assiut University, using a movable bed tilting channel 20 m long, 30 cm wide, and 50 cm high, using fourteen types of curved dissipaters with different arrangements as shown in Table 2. It is worth mentioning that, in this first part of our paper, we will introduce a comparative analysis for the efficiency of different types of energy dissipaters available in the literature review. The most effective types of the previously studied dissipaters will be put in a comparison with our new dissipaters from the two above mentioned points of view, and the results will be presented in the second part of this paper later.
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Karami, Hojat, Abdollah Ardeshir, Mojtaba Saneie, and S. Amin Salamatian. "Prediction of time variation of scour depth around spur dikes using neural networks." Journal of Hydroinformatics 14, no. 1 (April 23, 2011): 180–91. http://dx.doi.org/10.2166/hydro.2011.106.
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The maximum depth of scouring around spur dikes plays an important role in the hydraulic design process. There have been many studies on the maximum depth of scouring, but there is little information available on the time variation of scour depth. In this paper, the time variation of scouring around the first spur dike in a series was investigated experimentally. Experiments were carried out in four different bed materials under different flow intensities (U/Ucr). To achieve a time development of scouring around the first spur dike, more than 750 sets of experimental data were collected. The results showed that 70–90% of the equilibrium scour depths were occurring during the initial 20% of the overall time of scouring. Based on the data analysis, a regression model and artificial neural networks (ANNs) were developed. The models were compared with other empirical equations in the literature. However, the results showed that the developed regression model is quite accurate and more practical, but the ANN models by feed forward back propagation and radial basis function provide a better prediction of observation. Finally, by sensitivity analysis, the most and the least effective parameters, which affected time variation of scouring, were determined.
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Hamilton, A. S., and R. D. Moore. "Winter streamflow variability in two groundwater-fed sub-Arctic rivers, Yukon Territory, Canada." Canadian Journal of Civil Engineering 23, no. 6 (December 1, 1996): 1249–59. http://dx.doi.org/10.1139/l96-934.
Full textAbstract:
Frequent discharge measurements were made during the winter of 1994–1995 in two groundwater-fed streams near Whitehorse, Yukon Territory, to evaluate the nature and causes of winter discharge variability in sub-Arctic rivers. Observations were also made of near-stream hydraulic head, snowmelt percolation, and water quality. A linear reservoir model provided a poor fit to the streamflow recessions at both rivers, whereas three relatively complex models provided good fits to the data used for calibration. A pronounced discharge depression occurred at M'Clintock River associated with an increase in stage at freeze-up. The volume of water represented by the depression was about three times the maximum amount that could be accounted for by channel storage. This discrepancy could have been caused by stream–aquifer interactions. Piezometric observations were consistent with a reversal of hydraulic gradient across the stream bed, which would block or reduce groundwater inflow, as well as cause water to go into bank storage. A sustained discharge depression did not occur at Ibex River, probably because the volume of channel storage is small with respect to discharge and could be satisfied over the period of freeze-up without measurable deviation from the recession trend, and because the near-stream hydraulic gradients were strong enough not to be influenced by stage increases. Discharge at Ibex River was uncorrelated with air temperature. At M'Clintock River, residuals from the layered linear reservoir model appeared to be weakly correlated with air temperature. Key words: baseflow, river ice, winter, Yukon Territory, streamflow, stream–aquifer interactions.
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Li, Shicheng, Qiulin Li, and James Yang. "CFD Modelling of a Stepped Spillway with Various Step Layouts." Mathematical Problems in Engineering 2019 (November 28, 2019): 1–11. http://dx.doi.org/10.1155/2019/6215739.
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A traditional stepped spillway is prone to cavitation risks. To improve its hydraulic behaviors, distorted step faces and pool weirs are devised. By numerical modelling, comparative studies are conducted to look into the flow features. The pressures on step surfaces of the unconventional layouts exhibit 3D distributions. Pool weirs are essential in increasing both the min. and max. pressure loads. Pressures on the downstream bed show a unique pattern for V- and inverted V-shaped models, with the extreme pressures at the sidewalls for the former and at the central plane for the latter. Symmetrical secondary flows are formed in V- and inverted V-shaped cases with different patterns. Distributions of turbulent kinetic energy suggest differences in flow motions in all cases. Furthermore, the relative energy loss of flat setups is ∼5.4% lower than that of the pooled ones with the same step face angle; inverting the face angle does not give rise to noticeable change. The results provide reference for relevant projects.
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Tallent, James R., Takao Yamashita, and Yoshito Tsuchiya. "FIELD CALCULATIONS OF WAVE ENERGY DISSIPATION AND RELATED BEACH PROFILE." Coastal Engineering Proceedings 1, no. 21 (January 29, 1988): 135. http://dx.doi.org/10.9753/icce.v21.135.
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The process by which wave energy dissipates across the surf zone and its affect on the bed profile is, of course, a topic of immediate concern and debate. Various concepts of the wave energy dissipation process have been modeled, however, additional research is needed before confidence can be placed in a particular calculation scheme. In addition to the problems associated with proper model derivation a method of application and result interpretation of actual surf zone field data must be devised and understood. This is, of course, prerequisite to any realistic use of a wave energy dissipation model in an engineering project. The following study was therefore conducted in order to examine the applicability of surf zone field data to wave energy dissipation models and to investigate the bed profile relationship. Two wave energy dissipation models were selected for comparison in this study, the 'Undertow Model'(UM) which is based on the conservation of wave energy flux across the surf zone (3), and the 'Turbulent Bore Model'(TBM) which is based on hydraulic jump theory (2). Individual waves were identified in the wave record by employing the zero up-crossing method, and wave energy calculations were based on small amplitude wave theory, Svendsen's nonlinearity parameter Bo (4), and the 1/3 Significant Wave classification.
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Vidal, Jean-Philippe, Sabine Moisan, Jean-Baptiste Faure, and Denis Dartus. "Towards a reasoned 1D river model calibration." Journal of Hydroinformatics 7, no. 2 (March 1, 2005): 91–104. http://dx.doi.org/10.2166/hydro.2005.0009.
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Model calibration remains a critical step in numerical modelling. After many attempts to automate this task in water-related domains, questions about the actual need for calibrating physics-based models are still open. This paper proposes a framework for good model calibration practice for end-users of 1D hydraulic simulation codes. This framework includes a formalisation of objects used in 1D river hydraulics along with a generic conceptual description of the model calibration process. It was implemented within a knowledge-based system integrating a simulation code and expert knowledge about model calibration. A prototype calibration support system was then built up with a specific simulation code solving subcritical unsteady flow equations for fixed-bed rivers. The framework for model calibration is composed of three independent levels related, respectively, to the generic task, to the application domain and to the simulation code itself. The first two knowledge levels can thus easily be reused to build calibration support systems for other application domains, like 2D hydrodynamics or physics-based rainfall–runoff modelling.
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Fortunato, V. A., F. L. Caneppele, R. Ribeiro, and J. A. Rabi. "Development of in-house lattice-Boltzmann simulator of bioreactors for wastewater treatment: basic concepts and initial results." Water Science and Technology 77, no. 3 (November 24, 2017): 838–47. http://dx.doi.org/10.2166/wst.2017.597.
Full textAbstract:
Abstract While computational modelling has increasingly supported wastewater bioreactor engineering, novel numerical techniques have been developed such as the lattice-Boltzmann method (LBM). With vinasse treatment as case study, this work is a first step towards a comprehensive LBM simulator of a continuous-flow anaerobic packed-bed reactor. Extensions from typical models comprise one-dimensional (besides time) dependence, species transport via convection and diffusion, and imposition of either Dirichlet or Danckwerts condition at inlet. The LBM simulator proved to be operational when simulating the bioreactor at different hydraulic retention times (HRTs). Simulated profiles show that stepwise feeding concentrations are smoothed as they are transported towards the bioreactor exit while concentrations increase or decrease in response to generation or degradation kinetics. Good fitting was observed for concentrations of acetic acid (2.1 kg-COD/m3 for HRT = 24 h) and butyric acid (1.3 kg-COD/m3 for HRT = 16 h) at the exit whereas other concentrations were numerically simulated at proper order of magnitude.