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1
Mesrobian, Chris Eden. "Concept Study of a High-Speed, Vertical Take-Off and Landing Aircraft." Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/35574.
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The purpose of the study was to evaluate the merits of the DiscRotor concept that combine the features of a retractable rotor system for vertical take-off and landing (VTOL) with an integral, circular wing for high-speed flight. Tests were conducted to generate basic aerodynamic characteristics of the DiscRotor in hover and in fixed-wing flight. To assess the DiscRotor during hover, small scale tests were conducted on a 3ft diameter rotor without the presence of a fuselage. A â hover rigâ was constructed capable of rotating the model rotor at speeds up to 3,500 RPM to reach tip speeds of 500fps. Thrust and torque generated by the rotating model were measured via a two-component load cell, and time averaged values were obtained for various speeds and pitch angles. It has been shown that the DiscRotor will perform well in hover. Ground Effects in hover were examined by simulating the ground with a movable, solid wall. The thrust was found to increase by 50% compared to the ground-independent case. Pressure distributions were measured on the ground and disc surfaces. Velocity measurements examined the flow field downstream of the rotor by traversing a seven hole velocity probe. A wake behind the rotor was shown to contract due to a low pressure region that develops downstream of the disc.
Wind tunnel experimentation was also performed to examine the fixed wing flight of the DiscRotor. These experiments were performed in the VA Tech 6â X6â Stability Tunnel. A model of the fuselage and a circular wing was fabricated based upon an initial sizing study completed by our partners at Boeing. Forces were directly measured via a six degree of freedom load cell, or balance, for free stream velocities up to 200fps. Reynolds numbers of 2 and 0.5 million have been investigated for multiple angles of attack. Low lift-to-drag ratios were found placing high power requirements for the DiscRotor during fixed-wing flight. By traversing a seven-hole velocity probe, velocities in a 2-D grid perpendicular to the flow were measured on the model. The strengths of shed vortices from the model were calculated. A method to improve fixed-wing performance was considered where two blades were extended from the disc. An increase of 0.17 in the CL was measured due to the interaction between the disc and blades.
This research utilized a wide range of experiments, with the aim of generating basic aerodynamic characteristics of the DiscRotor. A substantial amount of quantitative data was collected that could not be included in this document. Results aided in the initial designs of this aircraft for the purpose of evaluating the merit of the DiscRotor concept.
Master of Science
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Guerrero, Reyes Lizbeth. "Circular business opportunities : exploring a win-win-win situation from a design thinking perspective." Thesis, Mälardalens högskola, Innovation och produktrealisering, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-52706.
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The transport sector is one of the main contributors to greenhouse gas emissions worldwide. A current solution to this problem is the introduction of electric vehicles into our transport fleets. However, this solution comes with its challenges; for instance, the environmental impact of batteries once they reach their end-of-life. The circular economy is an approach to manage ecological electromobility issues while providing economic and societal wellbeing. A starting point for the implementation of a circular economy can be found in the implementation of circular business models. Because the circular economy requires its actors to think in systems, the collaboration between multiple stakeholders is essential. However, most circular business model frameworks are focusing on the focal firm, which is not sufficient to encourage cross-collaboration between organizations. Therefore, this study outlines the development of a new framework that focuses on a multi-stakeholder perspective. I propose the “framework for multi-stakeholder circular business model innovation” to explore win-win-win scenarios for the management of 2LB. I conducted a study in collaboration with Svealandstrafiken, Mälarenergi and Västerås Stad. The organizations were involved in data collection via a series of interviews and the validation of the framework through a workshop. The proposed framework consists of a process of four phases subdivided into eight steps that meant to address key challenges organizations are facing to achieve circularity. Within these four phases, the framework encourages discussions on shared values and visions between all stakeholders at an early stage. As a consequence, better collaborations and relationships are formed, which positively benefits the development of circular business models.
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Christopoulos, George P. "Oscillating-flow wind tunnel studies for a circulation control circular cylinder." Thesis, Monterey, California. Naval Postgraduate School, 1991. http://hdl.handle.net/10945/28435.
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Nguyen-Sy, Lam. "The theoretical modelling of circular shallow foundation for offshore wind turbines." Thesis, University of Oxford, 2005. http://ora.ox.ac.uk/objects/uuid:fa4000fb-8de6-4093-b528-3e60d774dea0.
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Currently, much research is being directed at alternative energy sources to supply power for modern life of today and the future. One of the most promising sources is wind energy which can provide electrical power using wind turbines. The increase in the use of this type of energy requires greater consideration of design, installation and especially the cost of offshore wind turbines. This thesis will discuss the modelling of a novel type of shallow foundation for wind turbines under combined loads. The footing considered in this research is a circular caisson, which can be installed by the suction technique. The combined loads applied to this footing will be in three-dimensional space, with six degrees of freedom of external forces due to environmental conditions. At the same time, during the process of building up the model for a caisson, the theoretical analyses for shallow circular flat footing and spudcans also are established with the same principle. The responses of the soil will be considered in both elastic and plastic stages of behaviour, by using the framework of continuous plasticity based on thermodynamic principles. During this investigation, it is necessary to compare the numerical results with available experimental data to estimate suitable values of factors required to model each type of soil. There are five main goals of development of the model. Firstly, a new expression for plasticity theory which includes an experimentally determined single yield function is used to model the effects of combined cyclic loading of a circular footing on the behaviour of both sand and clay. This formulation based on thermodynamics allows the derivation of plastic solutions which automatically obey the laws of thermodynamics without any further assumptions. A result of this advantage is that non-associate plasticity, which is known to be a proper approximation for geotechnical material behaviour, is obtained logically and naturally. A FORTRAN source code called ISIS has been written as a tool for numerical analysis. Secondly, since there are some characteristics of the geometric shape and installation method which are quite different from that of spudcans and circular flat footing, another objective of this study is to adapt the current model which has been developed in ISIS for spudcans to the specific needs of caissons. The third goal of this research is the simulation of continuous loading history and a smooth transition in the stress-strain relationship from elastic to plastic behaviour. The model is developed from a single-yield-surface model to a continuous plasticity model (with an infinite number of yield surfaces) and then is discretized to a multiple-yield-surface model which can be implemented by numerical calculation to be able to capture with reasonable precision the hysteretic response of a foundation under cyclic loading. This can not be described by a conventional single-yield-surface model. Fourthly, as a method to simplify the numerical difficulties arising from the calculation process, a rate-dependent solution will be introduced. This modification is implemented by changing the dissipation function derived from the second law of thermodynamics. Finally, in order to control the model to capture the real behaviour, many parameters are proposed. A parametric study will be implemented to show the effects of these parameters on the solution.
5
Miranda, Sergio. "Active Control of Separated Flow over a Circular-Arc Airfoil." Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/34411.
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An experimental study of active control of fully separated flow over a symmetrical circular-arc airfoil at high angles of attack was performed. The experiments were carried out in a low-speed, open circuit wind tunnel. Angles of attack from 10 to 40 degrees were tested. Low-power input, unsteady excitation was applied to the leading or trailing edge shear layers. The actuation was provided by the periodic oscillation of a 4-percent-chord flap placed on the suction side of the airfoil and facing the sharp edge. Vortex-shedding frequencies were measured and harmonic combinations selected as the applied actuator frequencies.
Pressure measurements over the airfoil show that the control increased the normal force coefficient by up to 70%. This supports the idea of vortex capture in the time-averaged sense, enhancing the lift on the airfoil by managing the shear layer roll up.
The results indicate the viability of the control of large-scale flow fields by exploiting the natural amplification of disturbances triggered by small-scale actuators.
The application of flow control on sharp-edged aircraft wings could lead to improved maneuverability, innovative flight control and weight reduction. These can be achieved by inexpensive, low-power, rugged actuators.Master of Science
6
Zurell, Cory. "Aerodynamics of a circular cylinder inclined to airflow and wind-induced vibrations of dry, inclined cables at high wind speeds." Thesis, University of Ottawa (Canada), 2004. http://hdl.handle.net/10393/29184.
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Cable-stayed bridges are an efficient and elegant solution to bridging long spans. Though a widely used structural system, several significant issues are still unresolved regarding a cable-stayed bridge's performance, particularly with respect to the response of the cables to wind.
As tension members, stay cables have a very low diameter-to-span ratio such that the effect of bending stiffness on a cable's vibration characteristics is inconsequential. Coupled with this, stay cables have very little internal mechanical damping, thus they are quite susceptible to dynamic excitation. Several vibration mechanisms have been identified, however for some, including the potentially more damaging mechanisms, the required conditions and generating mechanisms are not completely understood.
Aerodynamically, a stay cable is simply a circular cylinder exposed to wind. A circular cylinder positioned normal to airflow is a touchstone topic in the fields of aerodynamics and fluid mechanics. A circular cylinder inclined to airflow, from a fundamental viewpoint, has been given very little attention considering the body of work concerning the former case.
The objective of this study was to determine the characteristics of the airflow about an inclined circular cylinder, and to determine and clarify necessary conditions for the generation of galloping vibrations and high-speed vortex vibrations in dry, inclined stay cables. A wind tunnel study was conducted in which a static circular cylinder was exposed, at varying relative wind-cylinder angles, to wind speeds corresponding to a Reynolds number range of 1 x 105 to 6 x 105 Surface pressure data was recorded to determine both the instantaneous and time-averaged pressures and forces on the section. Using the matrix computation software Matlab, programs were written to evaluate and analyse lift and drag forces, and pressure, lift, and drag coefficients. From the extensive data compiled, several significant conclusions concerning flow about an inclined or yawed cylinder and about the galloping and high-speed vortex vibration phenomena result.
Concerning flow about an inclined circular cylinder, the drag force coefficient is generally lower for lower relative inclination angles. This trend reverses over a small range of speeds within the critical Reynolds number range. Note that this and the following findings are based on the minimum inclination angle tested of 54.7°. (Abstract shortened by UMI.)
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Chen, Lei. "Buckling of circular steel cylindrical shells under different loading conditions." Thesis, University of Edinburgh, 2011. http://hdl.handle.net/1842/9435.
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Cylindrical shells are widely used in civil engineering. Examples include cooling towers, pipelines, nuclear containment vessels, steel silos and tanks for storage of bulk solids and liquids, and pressure vessels. The loading condition for these shells is quite varied depending on the function of the shell. Axial compression, global bending, external or internal pressure and wind loading are some of the most common loading forms for realistic structures. The failure of these cylindrical shell structures is often controlled by elastic or elastic-plastic buckling failure. Yield failure may occur in thick cylinders in some situations. A cylindrical shell under different loading conditions may display quite different buckling behaviour. The objective of this thesis is to investigate the characteristics of different buckling behaviours of cylindrical shell structures under axial compression, global bending, uniform external pressure and wind pressure. Some challenging practical problems in the design of these shell structures are explored. This thesis is expected to have some far-reaching impacts in defining how to design cylindrical shell structures to give them adequate strength to resist extreme events. Many aspects will be based on the latest Eurocode (EN 1993-1-6, 2007) and Recommendations (ECCS EDR5, 2008). The results show both some strength and some weaknesses in the Eurocode in design of shell structures. New methods are proposed for some practical problems. Some new conclusions and suggestions are derived and are expected to provide some useful knowledge for the improvement of the Eurocode in cylindrical shell design in general.
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Carrera, Fernando Henrique. "Estudo numérico para a determinação das pressões devidas a ação do vento em torres metálicas de seção circular /." Ilha Solteira : [s.n.], 2007. http://hdl.handle.net/11449/91496.
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Orientador: Renato Bertolino JúniorBanca: Haroldo de Mayo Bernardes
Banca: João Alberto Venegas Requena
Resumo: O presente trabalho tem por objetivo obter numericamente os valores das distribuições de pressões devidas a ação do vento e seus respectivos coeficientes de pressões de formas externos em torres de seção circular. As distribuições de pressões nas torres são determinadas através da simulação numérica, utilizando-se o programa ANSYS 9.0, considerando-se a interação fluido-estrutura. Para a simulação numérica, a geometria da torre foi modelada tridimensionalmente, considerando como fluido o ar no qual a edificação está inserida. As distribuições de pressão foram determinadas para relações geométricas em planta da torre, entre a altura e o diâmetro (h/d), para valores menores ou iguais a 10. Posteriormente, comparam-se os resultados numéricos obtidos na simulação através do ANSYS com os valores apresentados pela norma NBR-6123:1988, a fim de verificar a viabilidade da utilização da simulação numérica na obtenção das distribuições de pressão em outras estruturas.
Abstract: The present work has for objective to obtain the distributions pressures values the wind actions in tower with circular section. The values of the distributions pressures are obtained to the numeric simulation, using the ANSYS 9.0 software and considering the flow structure interaction. In the numeric simulation, the tower geometry was considered in 3D dimension, and the flowed it is the air. The distributions pressures were certain for geometry relationships between the height and the diameter (h/d), for values smaller or equal than 10. Later, the ANSYS numeric results are compared with the presents values by the NBR 6123:1998, in order to verify the viability numeric simulation used for obtaining the pressures distributions in other structures.
Mestre
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Fisher, David T. "Wind tunnel performance comparative test results of a circular cylinder and 50% ellipse tailboom for circulation control antitorque applications." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1994. http://handle.dtic.mil/100.2/ADA283335.
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Carrera, Fernando Henrique [UNESP]. "Estudo numérico para a determinação das pressões devidas a ação do vento em torres metálicas de seção circular." Universidade Estadual Paulista (UNESP), 2007. http://hdl.handle.net/11449/91496.
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O presente trabalho tem por objetivo obter numericamente os valores das distribuições de pressões devidas a ação do vento e seus respectivos coeficientes de pressões de formas externos em torres de seção circular. As distribuições de pressões nas torres são determinadas através da simulação numérica, utilizando-se o programa ANSYS 9.0, considerando-se a interação fluido-estrutura. Para a simulação numérica, a geometria da torre foi modelada tridimensionalmente, considerando como fluido o ar no qual a edificação está inserida. As distribuições de pressão foram determinadas para relações geométricas em planta da torre, entre a altura e o diâmetro (h/d), para valores menores ou iguais a 10. Posteriormente, comparam-se os resultados numéricos obtidos na simulação através do ANSYS com os valores apresentados pela norma NBR-6123:1988, a fim de verificar a viabilidade da utilização da simulação numérica na obtenção das distribuições de pressão em outras estruturas.
The present work has for objective to obtain the distributions pressures values the wind actions in tower with circular section. The values of the distributions pressures are obtained to the numeric simulation, using the ANSYS 9.0 software and considering the flow structure interaction. In the numeric simulation, the tower geometry was considered in 3D dimension, and the flowed it is the air. The distributions pressures were certain for geometry relationships between the height and the diameter (h/d), for values smaller or equal than 10. Later, the ANSYS numeric results are compared with the presents values by the NBR 6123:1998, in order to verify the viability numeric simulation used for obtaining the pressures distributions in other structures.
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Tuling, S. "An engineering method for modeling the interaction of circular bodies and very low aspect ratio cruciform wings at supersonic speeds." Thesis, University of the West of England, Bristol, 2013. http://eprints.uwe.ac.uk/20056/.
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An engineering method using a 2D unsteady potential formulation (called the free vortex model or FVM) has been developed to predict the normal force, centre-of-pressure and vortex position for cruciform wing-body combinations in the “plus” orientation, at supersonic speeds and cross flow Mach numbers less than or equal to 0.55 up to angles of attack 20◦. The wings are of very low aspect ratio ( ≤ 0.1), have taper ratios greater than 0.85 (or significant side edges) and have low span to body diameter ratios ( ≤ 1.5). The method predicts the position and subsequent loads imposed by the vortex along the length on the wing-body combination by determining the shed vorticity using Jorgensen’s modified Newtonian impact method. The vortex position is well predicted for angles of attack from 4◦ until symmetric vortex shedding occurs, whilst the normal force is well predicted from 0◦. The centre-of-pressure is predicted further aft at the low angles and further forward at the high angles of attack. If this method is used in combination with the single concentrated vortex of Bryson applied to cruciform wing-body combinations the vortex positions prediction limitations at angles of attack less than 4◦ can be overcome. An investigation of the lee side flow field of cruciform wing-body configurations was also performed, and revealed that the vortex position is dependent upon the lee side secondary vortex separation characteristics. Other features revealed that symmetric vortex shedding occurs when both the region of flow outside the shed vortex sheet and reverse flow region are supersonic and a termination shock exists. The thesis also investigated the applica- tion of the discrete vortex model (DVM) method to cruciform wing-body combinations and found that the potential only formulation overpredicts the normal force, whilst the inclusion of boundary layer separation (and therefore modeling the secondary separation vortex) predicted the normal force very well. The application of the concentrated vortex method of Bryson was also investigated and found to be only applicable at low angles of attack (< 4◦).
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Adibi, Naeem. "Développement d’un indicateur d’évaluation d’impacts de la consommation des ressources : cas d'application à une extraction des matériaux versus un recyclage." Thesis, Ecole centrale de Lille, 2016. http://www.theses.fr/2016ECLI0013/document.
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L’augmentation de la consommation de ressources suscite des préoccupations quant à leur disponibilité. Ces dernières années, les organisations nationales et internationales ont défini l’approvisionnement durable des ressources et la mise en place d’une économie circulaire comme des objectifs centraux de leurs stratégies à court et long termes.Dans ce contexte, différentes approches méthodologiques relevant de l’Analyse du Cycle de Vie (ACV) sont utilisées pour caractériser l'impact de l'épuisement des ressources. Les approches actuelles fournissent néanmoins des visions partielles, car dépendantes de données disponibles limitées, et ne reflètent pas les défis de la société en lien avec cette question des ressources.La méthode et les facteurs nouvellement développés fournissent une vision plus exhaustive de la disponibilité des ressources et peuvent être utilisés dans des analyses du cycle de vie ou dans des approches d'économie circulaire. Ce travail fut produit en partenariat avec le cd2e et le pôle de compétitivité Team². Il a également été réalisé en collaboration avec le bureau d’études et d’expertise en ACV, CyclecoIncrease in resource demand raises concerns over their availability. In the recent years, national and international institutions have targeted sustainable resource supply and new economy models (e.g. circular economy, etc.) as a goal of their short- and long-term strategies. In this context, different methodological approaches under Life Cycle Assessment (LCA) framework are used to address the impact of resource depletion. However, they provide partial visions, based on limited available data, and do not reflect society challenges related to the resources. The newly developed factors and the LCIA method provide a more exhaustive vision through the availability of resources and may be used in Life Cycle Assessment or circular economy approaches. This work is done in partnership with the cd2e and Team2 cluster. It is also carried out in collaboration with CYCLeco Life Cycle Assessment Experts
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Masterson, Vanessa Anne. "Sense of place and culture in the landscape of home : Understanding social-ecological dynamics on the Wild Coast, South Africa." Doctoral thesis, Stockholms universitet, Stockholm Resilience Centre, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-135280.
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Development for sustainable poverty alleviation requires engagement with the values and cultural frames that enable or constrain communities to steward ecosystems and maintain their capacity to support human well-being. Rooted in a social-ecological systems (SES) perspective, this thesis explores the concept of sense of place to understand how emotional and cultural connections to place mediate human responses to change and influence interventions for development. Sense of place is both the attachments to place, as well as the descriptive meanings to which one is attached. Paper I presents an approach and agenda for studying sense of place in SES that emphasizes place attachment and meaning underlying stewardship actions and responses to change. This is empirically explored through a case study on the Wild Coast, South Africa - an area with multiple contested meanings. In this former Bantustan (an area set aside for black South Africans), Apartheid created interdependence between small-holder agriculture and labour migration, where rural homesteads relied on remittances from migrant household members. Today, the contribution of agriculture to livelihoods has declined and many households rely on income from social grants. Interacting social and ecological factors in this region have resulted in social-ecological trap conditions and circular migration continues to be the pattern. Community conservation and ecotourism is one strategy for local socio-economic development. Papers II and III explore community tensions around a proposed nature reserve declaration. In Paper II, a focus on the meanings of locally-defined ecotopes (e.g. forest and abandoned fields) illuminates the interpretations of underlying social-ecological processes. Paper III examines the use of place meanings in narratives of change to show tensions in the discourse of win-win conservation. The stalling of this particular intervention indicates the importance of engaging with multiple meanings of place and the cultural importance of nature. Papers IV and V focus on declining agriculture and continued labour migration. From a theoretical model of people’s abilities, desires and opportunities, Paper IV develops a typology of responses that may contribute to maintaining or resolving social-ecological traps. For this case study, the model identifies the mismatch between i) cultural expectations that frame the desire to farm, and ii) the decline in opportunities for off-farm income to support agriculture. Paper V demonstrates that these expectations are expressed in the idea of emakhaya (the rural landscape of home) as well as reinforced through cultural rituals. The paper identifies a place-based social contract between the living and the ancestors that helps to maintain circular migration and agricultural practices. This suggests that sense of place contributes to system inertia but may also offer opportunities for stewardship. Sense of place is socially constructed as well as produced through experience in ecosystems, and thus constitutes an emergent property of SES. The thesis demonstrates the use of participatory methods to produce an inclusive understanding of place and SES dynamics. The application of place meanings through these methods facilitates critical engagement with imposed interventions. Finally, the thesis shows that sense of place and culture are key for understanding inertia in SES and the capacity for transformation towards stewardship.At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Manuscript. Paper 2: Manuscript. Paper 3: Manuscript. Paper 5: Manuscript.
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Kumar, Bhunesh. "Design of Harmonic Filters for Renewable Energy Applications." Thesis, Högskolan på Gotland, Institutionen för kultur, energi och miljö, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:hgo:diva-1862.
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Harmonics are created by non-linear devices connected to the power system. Power system harmonics are multiples of the fundamental power system frequency and these harmonic frequencies can create distorted voltages and currents. Distortion of voltages and currents can affect the power system adversely causing power quality problems. Therefore, estimation of harmonics is of high importance for efficiency of the power system network. The problem of harmonic loss evaluation is of growing importance for renewable power system industry by impacting the operating costs and the useful life of the system components. Non-linear devices such as power electronics converters can inject harmonics alternating currents (AC) in the electrical power system. The number of sensitive loads that require ideal sinusoidal supply voltage for their proper operation has been increasing. To maintain the quality limits proposed by standards to protect the sensitive loads, it is necessary to include some form of filtering device to the power system. Harmonics also increases overall reactive power demanded by equivalent load. Filters have been devised to achieve an optimal control strategy for harmonic alleviation problems. To achieve an acceptable distortion, increase the power quality and to reduce the harmonics hence several three phase filter banks are used and connected in parallel. In this thesis, high order harmonics cases have been suppressed by employing variants of Butterworth, Chebyshev and Cauer filters. MATLAB/SIMULINK wind farm model was used to generate and analyze the different harmonics magnitude and frequency. High voltage direct current (HVDC) lines for an electrical grid that is more than50km far away wind farm generation plant was investigated for harmonics. These HVDC lines are also used in offshore wind farm plant. Investigated three-phase harmonics filters are shunt elements that are used in power systems for decreasing voltage distortion and for correcting the power factor. Renewable energy sources are not the stable source of energy generation like wind, solar and tidal e.t.c. Though they are secondary sources of generation and hard to connect with electrical grid. In near future the technique is to use the wave digital filter (WDF) or circulator-tree wave digital filter (CTWDF) for the renewable energy application can be employed to mitigate the harmonics. These WDF and CTWDF can b eused in HVDC lines and smart grid applications. A preliminary analysis is conducted for such a study.
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Lin, Tan-Yi, and 林坦誼. "Experimental Study of Wind Pressure on Semi-circular Greenhouses." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/11069946378526634409.
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碩士國立中央大學
土木工程學系
104
Abstract Taiwan is located in the west Pacific typhoon-prone area, and the strong wind during typhoons could bring severe damages to the farm houses and greenhouses. This research uses wind tunnel experiments to study the pressure distribution on semi-circular greenhouses. The instantaneous pressures on the surface of the greenhouse are measured by a multi-channel pressure scanner under different wind directions and arrangements. The experimental results reveal that the time-averaged pressure coefficient of oblique wind (wind direction 22.5o) is larger than that of wind direction normal to the ridge line (wind direction 0o). In addition, although the time-averaged pressure coefficients are within the values suggested by the Wind Code of Taiwan, but the peak pressure is several times larger than the time-average pressure. The gust response factor of the Wind Code is not sufficient to protect the semi-circular greenhouses against the peak pressure on the greenhouse roof. Based on the measured data and the quasi-steady theory, a peak pressure factor, g, was used to predict the peak pressure coefficient Cpeak. The experimental results validate the capability of the peak pressure factor to predict Cpeak. However, the peak pressure factor is dependent on the method to calculate the peak pressure. The peak pressure factor g = 3.81, regardless using moving average or not. But the peak pressure factors Gp is dependent on the turbulence intensity Iu. The results of this study not only provide the needed information for the structural design of the arch-roof greenhouse but also to facilitate a better understanding of the separation phenomenon and peak pressure around circular-bodies.
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Berndt, Roland Gunther. "Adaptive wall wind tunnel investigation of a circulation controlled circular cylinder." Thesis, 2016. http://hdl.handle.net/10539/20664.
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Yang, Win Chung, and 楊文忠. "Critical Wind Velocity of a Circular Curved Beam by Finite Element Method." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/14677454604645547204.
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Mu-YaoChen and 陳慕堯. "Wind Sensor Design based on Vortex Shedding Phenomena from a Circular Cylinder." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/70201282550692385808.
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碩士國立成功大學
航空太空工程學系
103
Flow over a bluff body has been studied extensively for the past century and the well-known Kármán vortex street phenomena is widely used in practice. This thesis presents the principle and description of the new, entirely static device for measurement of wind speed using the vortex shedding phenomena behind a circular cylinder, furthermore an anemometer which can catch the instantaneous wind speed and acclimate to the wind direction variations excellently. In this research the development of wind sensor based on vortex shedding phenomena from a circular cylinder can break into three parts including CFD numerical simulation, wind tunnel experiment, and on-site measurement respectively. A simple wind speed signal analysis algorithm based on the Hilbert-Huang transform (HHT) is first presented. However due to empirical difficulties from turbulence effects in wind tunnel experiments and wind gust fluctuations during on-site measurement, a new modified wind speed signal analysis algorithm is developed to deal with signal noises issues. By using band-pass filtering process and data binning average process, the vortex anemometer can result the wind speed with an accuracy below 1% if the coming flow wind speed is more than 10 m/sec in this research. This vortex anemometer has the advantages of long-term stability, well repeatability, low maintenance costs, and absence of moving parts; moreover an excellent accuracy with high dynamic frequency response which provides a new revolution and choice of measuring the wind speed in turbulent flow.
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Barrera, Emilia Ayres de la. "Exploring Circular Economy as an Innovative Approach Through a Wine Tourism Itinerary." Master's thesis, 2019. https://hdl.handle.net/10216/126700.
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Wen, Horng Shen, and 溫宏盛. "The Application of Expert System in Wind Resistant Design of Circular Cylinder Structures." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/87644778402749445946.
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碩士淡江大學
土木工程學系
88
Taiwan is located in the West Pacific area that typhoons attack. Therefore, the wind effect on high structures is an important issue. Especially, chimneys are a kind of static determined structure. Once a local structural failure occurs, it will lead to the lost of its whole function. Hence, sensibly analyzing the wind load condition in order to design economic and safe chimneys is the main topic of the research. Besides, an excellent design is not only based on strict structural theory but also accompanied by accumulated design experience. So the goal of the research is to develop an expert system in wind resistant design of circular cylinder structures, which incorporate both the theory of wind engineering, code of structural design and the experience-based knowledge of design experts. Through the system users can get preliminary structural design suggestion, then progress to more detailed work of design. The behavior of structures subjected to wind loads is calculated by static forces and empirical formula in domestic codes, which cannot fully describe the random characteristics of wind loads. Therefore, the theoretical analysis part of our research considered the aerodynamic damping and aeroelastic lock-in phenomena between a structure and oncoming flow. Mathematical models can be used to accurately predict along-wind response. Therefore, we can use structural dynamics and random vibration theories to make a reasonable analysis. As for across-wind response, we adopt the aerodynamic damping analysis model brought out by Vickery and Basu in 1983. In the aspect of structural design, this system refers to the most common standards: Standard practice for the design and construction of cast-in-place reinforced concrete chimneys ACI 307-98. Kappa-PC, an expert system construction tool developed by IntelliCorp., was used to build the system architecture. Based on the characters of the knowledge to be represented, rule-based reasoning and object-oriented programming were used accordingly to build the system. Besides, the system integrates necessary numerical and structural analysis programs accompanied with a friendly user interface to perform the design and analysis of chimneys. Finally, documented cases from literature were used to test the accuracy of the system.
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Jen, Chou Li, and 周立人. "The Application of Web-Based Expert System in Structural Engineering─Wind Resistant Design of Circular Cylinder Structures." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/57385187213512968178.
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碩士淡江大學
土木工程學系
89
Over the past years, Internet is expanding all over the world. Moreover, with the process of high-speed network and the development of WWW, it is a trend to cybernate computer programs. On the other hand, knowledge management using expert systems in structural engineering become an issue recently. Although expert systems provide simple and convenient working environment for users, yet limited by the needs of advanced hardware and compatible runtime environment prevent the popularity of standalone expert systems today. The aim of the thesis is to build a web-based expert system model for structural design using WWW technologies. The client-server and cross-platform approach resolves analysis program integration, hardware compatibility, program maintenance and runtime license fee problems. Users can operate the expert system on the server with standard WWW browsers without installing expert system and/or any supporting software. Knowledge base and programs can be centrally maintained and updated. Because the system is on the Internet, it supports multiple sessions of different users performing wind resistant design of circular cylinder structure at the same time. As to the theories of this research, we consider Aerodynamic damping and Aeroelastic lock-in phenomena between a structure and oncoming flow. We use Davenport’s method of along-wind analysis combining structure dynamics and random vibration theories on along-wind responses. As for across-wind responses, we adopt the aerodynamic damping analysis model brought out by Vickery and Basu in 1983. This system refers to the most common standards: Standard practice for the design and construction of cast-in-place reinforced concrete chimneys ACI307-98 on structural design. WebExpert developed by Wise Web Ware, was used to implement the system. In addition, the system integrates numerical and structural analysis programs together with a friendly user interface implemented in HTML, JavaScript, etc.
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Chang, Wen-Cheng, and 張文誠. "Wind tunnel study on the dispersion of the airborne discharge interacting with semi-circular type of windbreak." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/70935009565593401217.
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Wu, Yi-Ching, and 吳宜青. "Wind tunnel study on the dispersion of continuously spilled heavy gas interacting with semi-circular type of windbreak." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/63088385313394083628.
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LIN, SHANG-AN, and 林上安. "The wind-tunnel testing of flow field in a duct transition from a circular to a rectangular cross-section." Thesis, 1987. http://ndltd.ncl.edu.tw/handle/63107250958298851220.
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Lin, Ming-Hung, and 林明泓. "The wind tunnel investigates the pressure distribution on the surface of three-dimensional circular cylinder in a uniform flow." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/09037853384983128196.
Full textAbstract:
碩士國立中央大學
土木工程研究所
91
This study experimentally investigates the pressure distribution on the surface of three-dimensional circular cylinder in a uniform flow. The experiments were carried out in a wind tunnel. The flow conditions include three different kinds of surface roughness. Instantaneous fluctuating wind pressures were measured by an electronic pressure scanner. Based on the pressure measurement, the distributions of mean pressure coefficient Cp, rms Cprms, and peak pressure Cpp were calculated. Also, the separation point and the location of minimum negative pressure will move toward upstream direction as surface roughness increase. Compared to the results of Lee (2002), the moving range of separation point will decrease as surface roughness increase. The experimental results also revealed that the probability of pressure fluctuations for positive pressure is close to the Gaussian distribution function. On the other hand, negative pressure side was skewed and did not necessary follow Gaussian distribution.
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Schutte, Willem Daniël. "Nonparametric estimation of the off-pulse interval(s) of a pulsar light curve / Willem Daniël Schutte." Thesis, 2014. http://hdl.handle.net/10394/12199.
Full textAbstract:
The main objective of this thesis is the development of a nonparametric sequential estimation
technique for the off-pulse interval(s) of a source function originating from a pulsar. It is important
to identify the off-pulse interval of each pulsar accurately, since the properties of the off-pulse
emissions are further researched by astrophysicists in an attempt to detect potential emissions
from the associated pulsar wind nebula (PWN). The identification technique currently used in the
literature is subjective in nature, since it is based on the visual inspection of the histogram estimate
of the pulsar light curve. The developed nonparametric estimation technique is not only objective
in nature, but also accurate in the estimation of the off-pulse interval of a pulsar, as evident from
the simulation study and the application of the developed technique to observed pulsar data.
The first two chapters of this thesis are devoted to a literature study that provides background
information on the pulsar environment and -ray astronomy, together with an explanation of the
on-pulse and off-pulse interval of a pulsar and the importance thereof for the present study. This
is followed by a discussion on some fundamental circular statistical ideas, as well as an overview
of kernel density estimation techniques. These two statistical topics are then united in order to
illustrate kernel density estimation techniques applied to circular data, since this concept is the
starting point of the developed nonparametric sequential estimation technique.
Once the basic theoretical background of the pulsar environment and circular kernel density
estimation has been established, the new sequential off-pulse interval estimator is formulated. The
estimation technique will be referred to as `SOPIE'. A number of tuning parameters form part
of SOPIE, and therefore the performed simulation study not only serves as an evaluation of the
performance of SOPIE, but also as a mechanism to establish which tuning parameter configurations
consistently perform better than some other configurations.
In conclusion, the optimal parameter configurations are utilised in the application of SOPIE to
pulsar data. For several pulsars, the sequential off-pulse interval estimators are compared to the
off-pulse intervals published in research papers, which were identified with the subjective \eye-ball"
technique. It is found that the sequential off-pulse interval estimators are closely related to the
off-pulse intervals identified with subjective visual inspection, with the benefit that the estimated
intervals are objectively obtained with a nonparametric estimation technique.PhD (Statistics), North-West University, Potchefstroom Campus, 2014
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Zingan, Valentin Nikolaevich. "Discontinuous Galerkin Finite Element Method for the Nonlinear Hyperbolic Problems with Entropy-Based Artificial Viscosity Stabilization." Thesis, 2012. http://hdl.handle.net/1969.1/ETD-TAMU-2012-05-10845.
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This work develops a discontinuous Galerkin finite element discretization of non- linear hyperbolic conservation equations with efficient and robust high order stabilization built on an entropy-based artificial viscosity approximation.
The solutions of equations are represented by elementwise polynomials of an arbitrary degree p > 0 which are continuous within each element but discontinuous on the boundaries. The discretization of equations in time is done by means of high order explicit Runge-Kutta methods identified with respective Butcher tableaux.
To stabilize a numerical solution in the vicinity of shock waves and simultaneously preserve the smooth parts from smearing, we add some reasonable amount of artificial viscosity in accordance with the physical principle of entropy production in the interior of shock waves. The viscosity coefficient is proportional to the local size of the residual of an entropy equation and is bounded from above by the first-order artificial viscosity defined by a local wave speed. Since the residual of an entropy equation is supposed to be vanishingly small in smooth regions (of the order of the Local Truncation Error) and arbitrarily large in shocks, the entropy viscosity is almost zero everywhere except the shocks, where it reaches the first-order upper bound.
One- and two-dimensional benchmark test cases are presented for nonlinear hyperbolic scalar conservation laws and the system of compressible Euler equations. These tests demonstrate the satisfactory stability properties of the method and optimal convergence rates as well. All numerical solutions to the test problems agree well with the reference solutions found in the literature.
We conclude that the new method developed in the present work is a valuable alternative to currently existing techniques of viscous stabilization.