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Dissertations / Theses on the topic 'Wind tunnel'
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1
Premnath, S. M. Jason. "A tolerant axisymmetric wind tunnel." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/28511.
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A solution to the current problem of wind tunnel wall interference could be achieved by ventilating the test section and thereby controlling the flow pattern around the model. The motivation for the slotted wall test section arises from the fact that a fully open jet and a fully closed jet introduce corrections of opposite sign to the wind tunnel data. This current work is limited to axisymmetric wind tunnels and solid blockage corrections.
Such a tolerant axisymmetric wind tunnel (TAWT), which does not need any correction to the measured flow quantities and which is also independent of the test model shape and size would find wide application in the field of industrial aerodynamics.
A numerical model based on a surface singularity potential flow method showed that at 70% OAR (open area ratio) for models of size up to 25% blockage and for three different shapes the tunnel design would yield results (coefficient of pressure) with less than 2% error while such models might need up to 75% data correction if tested in a solid wall wind tunnel.
Experiments indicated good agreement with the numerical investigation and at 60% OAR the TAWT gave results close to free air results for all the models tested (up to 25% blockage).Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate
2
Mujica, Fernández Fernando R. (Fernando René). "Lattice gas wind tunnel." Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/13444.
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3
Hickle, Curtis. "Wind Tunnel renovation, flow verification and flapping wing analysis." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2006. http://library.nps.navy.mil/uhtbin/hyperion/06Jun%5FHickle.pdf.
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Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, June 2006.Thesis Advisor(s):Dr. Kevin Jones and Dr. Garth Hobson. "June 2006." Includes bibliographical references (p.79-81). Also available in print.
4
Paul, Matthew G. "Wing Deflection Analysis of 3D Printed Wind Tunnel Models." DigitalCommons@CalPoly, 2017. https://digitalcommons.calpoly.edu/theses/1751.
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This work investigates the feasibility of producing small scale, low aerodynamic loading wind tunnel models, using FDM 3D printing methods, that are both structurally and aerodynamically representative in the wind tunnel. To verify the applicability of this approach, a 2.07% scale model of the NASA CRM was produced, whose wings were manufacturing using a Finite Deposition Modeling 3D printer. Experimental data was compared to numerical simulations to determine percent difference in wake distribution and wingtip deflection for multiple configurations.
Numerical simulation data taken in the form of CFD and FEA was used to validate data taken in the wind tunnel experiments. The experiment utilized a wake rake to measure 3 different spanwise locations of the wing for aerodynamic data, and a videogrammetry method was used to measure the deflection of the wingtips for structural data. Both numerical simulations and experiments were evaluated at Reynolds numbers of 258,000 and 362,000 at 0 degrees angle of attack, and 258,000 at 5 degrees angle of attack.
Results indicate that the wing wake minimum in the wind tunnel test had shifted approximately 8.8mm at the wingtip for the Nylon 910 wing at 258,000 Reynolds number for 0 degrees angle of attack when compared to CFD. Videogrammetry results indicate that the wing deflected 5.9mm, and has an 18.6% difference from observed deflection in FEA. This reveals the potential for small scale wind tunnel models to be more representative of true flight behavior for low loading scenarios.
5
Danis, Reed. "Investigating Forward Flight Multirotor Wind Tunnel Testing in a 3-by 4-foot Wind Tunnel." DigitalCommons@CalPoly, 2018. https://digitalcommons.calpoly.edu/theses/1909.
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Investigation of complex multirotor aerodynamic phenomena via wind tunnel experimentation is becoming extremely important with the rapid progress in advanced distributed propulsion VTOL concepts. Much of this experimentation is being performed in large, highly advanced tunnels. However, the proliferation of this class of vehicles extends to small aircraft used by small businesses, universities, and hobbyists without ready access to this level of test facility. Therefore, there is a need to investigate whether multirotor vehicles can be adequately tested in smaller wind tunnel facilities. A test rig for a 2.82-pound quadcopter was developed to perform powered testing in the Cal Poly Aerospace Department’s Low Speed Wind Tunnel, equipped with a 3-foot tall by 4-foot wide test section. The results were compared to data from similar tests performed in the U.S. Army 7-by 10-ft Wind Tunnel at NASA Ames. The two data sets did not show close agreement in absolute terms but demonstrated similar trends. Due to measurement uncertainties, the contribution of wind tunnel interference effects to this discrepancy in measurements was not able to be properly quantified, but is likely a major contributor. Flow visualization results demonstrated that tunnel interference effects can likely be minimized by testing at high tunnel speeds with the vehicle pitched 10-degrees or more downward. Suggestions towards avoiding the pitfalls inherent to multirotor wind tunnel testing are provided. Additionally, a modified form of the conventional lift-to-drag ratio is presented as a metric of electric multirotor aerodynamic efficiency.
6
Engel, Mark A. "A wind tunnel investigation of a wing-tip trailing vortex." Thesis, This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-01102009-063459/.
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7
Fitzgerald, Ryan Elizabeth. "Wind tunnel blockage corrections for propellers." College Park, Md.: University of Maryland, 2007. http://hdl.handle.net/1903/7363.
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Thesis (M.S.) -- University of Maryland, College Park, 2007.Thesis research directed by: Dept. of Aerospace Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
8
Lubitz, William David. "Near real time wind energy forecasting incorporating wind tunnel modeling /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2005. http://uclibs.org/PID/11984.
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9
Conan, Boris. "Wind resource accessment in complex terrain by wind tunnel modelling." Phd thesis, Université d'Orléans, 2012. http://tel.archives-ouvertes.fr/tel-00843645.
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To benefit from strong winds, an increasing number of wind turbines are placed in complex terrains. But complex terrains means complex flows and difficult wind resource assessment. This study proposed to use wind tunnel modelling to evaluate the wind in a complex topography. The goal of this study is to evaluate the possibilities of wind resources assessment by wind tunnel modelling and to quantify the important modelling parameters. The lower part of the atmosphere, the atmospheric boundary layer (ABL) is defined by a velocity and a turbulence gradient. The ABL is reproduced in the wind tunnel by placing obstacles and roughness elements of different size representative to the type of terrain desired. The flow produced in the wind tunnel is validated against field data and a wise choice of the obstacles is discussed to reproduce the desired wind profile. The right reproduction of the inflow conditions is found to be the most important parameter to reproduce. The choice of the area to reproduce around a site in usually difficult to make in order to keep a low scaling factor and to account for the surrounding topography. A series of tests on simplified hills helps the experimentalist in this choice by enlightening the longitudinal and vertical extension of the wake downstream different hills shapes. Finally, two complex topographies are studied in two wind tunnels, the Bolund hill in Denmark and the Alaiz mountain in Spain. The results are giving good results, 5 to 10 %, for predicting the wind speed but more scatter is observed for the modelling of the turbulence, up to 100 %. The laboratory simulation of atmospheric flows proves to be a demanding but reliable tool for the prediction of the mean wind speed in complex terrain.
10
Oliveira, Henrique Balona de Sá. "Wind erosion of biochar-amended soil: a wind tunnel experiment." Master's thesis, Universidade de Aveiro, 2014. http://hdl.handle.net/10773/14312.
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Mestrado em Engenharia do AmbienteBiochar application to soils has been reported in the scientific community as a possible means of improving agricultural productivity and, at the same time, as a powerful tool for carbon sequestration and climate change mitigation. However, current knowledge of biochar effects on soil functions and possible environmental threats is still not enough for a full-scale implementation. Erosion is one of the most serious and irreversible threats to soil and there is still no information if biochar may increase or decrease soil erosion rates. Soil erosion by wind is of particular interest for biochar, because of the low particle density and potential human exposure. The purpose of this study was to fill this knowledge gap by investigating the wind erosion potential of biochar-amended soil with a focus on the effect of soil moisture content, using a laboratory wind tunnel. Firstly, experimental tests were implemented in the DAO wind tunnel to define a robust wind erosion methodology in a facility only used for smoke studies. Sediment collecting methods, dust fraction analysis and wind velocity range were the main factors that required investigation. The erosion of biochar-amended soil (10% m m-1) and control soil (sandy soil) was simulated by positioning a tray divided in a sample area and an area for creeping particles, inside the test section of the wind tunnel. To determine the effect of soil moisture content on the erosion potential, four moisture contents were used: 0.2%, 1.7%, 4% and 8% (gravimetric). The wind tunnel simulations were performed with the duration of 15 minutes at a wind velocity of 7 m s-1. The samples of collected sediment were oven-dried and weighed to give the sediment loss as consequence of the erosion event. Results on the erosion simulations for control and biochar-amended soil with the wind flow velocity of 7 m s-1 (small erosion event) indicated that only biochar particles were displaced. Erosion of biochar-amended soil was similar for 0.2%, 1.7% and 4.0% and despite a sediment loss reduction of 50% from 4% MC to the higher MC, 8%, this latter was not identified as the threshold MC for the moment when erosion ceases to exist. As for mineral particles, after 4% MC there was no sediment collected indicating this MC as the threshold, even though a reduced mass of particles eroded for the smaller MCs. Further future tests are needed to build a more comprehensive understanding of wind erosion of biochar-amended soils. Relevant factors to include are: higher wind velocities representative of medium and high erosion events, as well as higher MCs to identify when erosion of biochar particles will stop completely. Secondly, based on the results found in the present study, other soil types and biochar types warrant further investigation. Studies like this contribute for the understanding of the effects of biochar application to soil functions, as well as the behaviour and fate of this material, which are indispensable for the development of adequate biochar regulations and policies.
A aplicação de biochar no solo tem sido referida na comunidade científica como um possível meio para melhorar a produtividade agrícola e, ao mesmo tempo, como um instrumento para sequestro de carbono e mitigação de alterações climáticas. Contudo, o conhecimento actual sobre os efeitos do biochar nas funções do solo e possíveis ameaças ambientais não é, ainda, suficiente para uma implementação em larga escala. A erosão é uma das mais sérias e irreversíveis ameaças ao solo e não existe, ainda, informação se o biochar pode aumentar ou reduzir os níveis de erosão. A erosão do solo pelo vento é de particular interesse para o biochar, devido à reduzida densidade das partículas e à potencial exposição humana. O objectivo deste trabalho foi preencher esta falha ao investigar o potencial de erosão do solo melhorado com biochar com enfoque no efeito do teor de humidade, usando um túnel de vento. Primeiramente, testes experimentais foram implementados no túnel de vento do DAO para definir uma metodologia robusta de erosão eólica numa estrutura, até então, apenas usada para estudos de dispersão de poluentes. A colecta do sedimento, análise de fracção de poeiras e a gama de velocidades foram os factores principais que necessitaram de investigação. A erosão de solo com biochar (10% m m-1) e de solo de controle (solo arenoso) foi simulada posicionando um tabuleiro dividido em área de amostra e área para partículas de rolamento, dentro da secção de teste do túnel de vento. Para determinar o efeito do teor de humidade do solo no potencial de erosão, quatro teores de humidade foram usados: 0.2%, 1.7%, 4% and 8% (gravimétricos). As simulações no túnel de vento foram realizadas com a duração de 15 minutos a uma velocidade do vento de 7 m s-1. As amostras de sedimento colectado foram secas e pesadas para fornecerem a perda de sedimento como consequência do evento de erosão. Os resultados das simulações de erosão para o controle e o solo melhorado com biochar, com a velocidade de 7 m s-1 (reduzido evento de erosão) indicaram que apenas partículas de biochar foram movidas. Erosão de solo com biochar foi semelhante para 0.2%, 1.7% and 4.0% e, apesar da redução da perda de sedimento em 50% do teor de 4% para para o teor mais alto, 8%, este último não foi identificado como sendo o limiar para o momento em que a erosão deixa de existir. Relativamente às partículas minerais, após o teor de 4% não houve sedimento colectado indicando este teor de humidade como o limiar, ainda que uma massa reduzida de partículas tenha sofrido erosão para teores mais reduzidos. Testes futuros são necessários para gerar um melhor conhecimento acerca de erosão de solo com biochar pelo vento. Factores relevantes a incluir são: maiores velocidades do vento, representativas de eventos de erosão médios e elevados, tal como maiores teores de humidade para identificar quando a erosão de partículas de biochar pára por completo. Em segundo lugar, com base nos resultados observados neste estudo, outro tipos de solo e biochar impõe mais investigação.Estudos como este contribuem para perceber os efeitos da aplicação de biochar nos solos, bem como o comportamento e destino deste material, que são indispensáveis para o desenvolvimento de regulamentos e políticas adequadas sobre biochar.
11
Allan, Mark. "A CFD investigation of wind tunnel interference on delta wing aerodynamics." Thesis, University of Glasgow, 2002. http://theses.gla.ac.uk/4081/.
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To explore the influence of wind tunnel test facilities on delta wing aerodynamics, the interference has been separated into two distinct types, wall interference and support structure interference. The wall interference effects have been split into three further components, tunnel blockage, side wall interference, and roof and floor interference. Splitting the tunnel influence in this way allows us to determine the most detrimental interference effects, thus allowing the wind tunnel engineer to design experiments accordingly. Euler and more realistic RANS simulations of tunnel interference have been conducted. To reduce the question of grid dependence when comparing solutions, a common "farfield grid" was created and tunnel grids were extracted. Before doing RANS simulations an analysis of various turbulence models was conducted. It was found that turbulence models have difficulty in predicting turbulence levels in leading edge vortices. As such modifications have been applied to the models which improve predictions. Despite vortex breakdown being widely regarded as an inviscid phenomenon, dependence on turbulence modelling has been exhibited. This is due to the vortex properties being altered with turbulent diffusion of vorticity when turbulence levels are too high. Both 1- and 2-equation models were assessed and it was concluded that a modified 2-equation k-w model was the most suitable of the models available (when compared against experimental results), and was therefore used in all subsequent simulations. From both Euler and RANS simulations it has been concluded that the effect of sidewall proximity significantly promotes vortex breakdown. Side wall induced velocity components increase the mean effective incidence of the wing, the helix angle and the strength of the vortices. The combination of these effects promotes vortex breakdown. Roof and floor proximity has little effect on vortex breakdown as does the frontal area blockage. Pitching simulations have shown that the promotion of vortex breakdown is not consistent on both the upstroke and downstroke. Break-down was observed to be prompted furthest at the higher incidence of the upstroke and on the downstroke. This highlights the dependency of tunnel interference on vortex strength.
12
Ross, Ian J. "Wind tunnel blockage corrections : an application to vertical-axis wind turbines /." Dayton, Ohio : University of Dayton, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1271306622.
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Thesis (M.S. in Aerospace Engineering) -- University of Dayton.Title from PDF t.p. (viewed 06/22/10). Advisor: Aaron Altman. Includes bibliographical references (p. 101-104). Available online via the OhioLINK ETD Center.
13
Kayisoglu, Bengi. "Investigation Of Wind Effects On Tall Buildings Through Wind Tunnel Testing." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613324/index.pdf.
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In recent years, especially in the crowded city-centers where land prizes have become extremely high, tall buildings with more than 30 floors have started to be designed and constructed in Turkey. On the other hand, the technical improvements have provided the opportunity of design and construction of more slender structures which are influenced by the wind actions more. If the building is flexible, wind can interact with it so the wind induced oscillations can be significantly magnified. In order to analyze the response of such buildings under wind effects, wind tunnel tests are accepted to be the most powerful tool all over the world. In this study, a series of tests were performed in Ankara Wind Tunnel on a model building in the shape of a rectangular prism. For the similitude of flow conditions, passive devices were designed. The response of the model building was measured through a high frequency base balance which was designed specifically for this case study. Through the tests, the effects of turbulence intensity, vortex shedding and wind angle of attack on the response of the building were questioned. Finally, the results were compared with the results of various technical specifications about wind.
14
Ross, Ian Jonathan. "Wind Tunnel Blockage Corrections: An Application to Vertical-Axis Wind Turbines." University of Dayton / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1271306622.
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Katirci, Argun. "Automation And Verification Of Ankara Wind Tunnel." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/12607692/index.pdf.
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All the operational and measurement systems of Ankara Wind Tunnel was modified to
operate automatically under the control of a central computer system programmed using
the Lab View programming language.
A cruciform air-to-air missile with triangular canard control and a trapezoidal wing
model was tested by a 35mm diameter internal balance at Mach 0.2 and data was
compared with the test data of the same model&rsquos test that was performed at NASA Langley Research Center.
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Abrahamsen, Ida Sinnes. "Wind tunnel model testing of offshore platforms." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for energi- og prosessteknikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18627.
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The purpose of this thesis is to highlight some of the areas of interest when it comes to wind tunnel experimenting of offshore platforms regarding stability concerns such as critical angles and wind overturning moment. Some important factors include design of tower geometry, the effect of surface roughness on drag, methods of calculating blockage corrections of wall interference and the generation of an atmospheric boundary layer to resemble full-scale conditions. Data obtained from wind tunnel experiments with two different models have been compared and discussed according to the areas of interest as mentioned above. Testing of platforms was done at NTNU with a six-component balance, measuring forces of drag, side and lift and moment of pitch, roll and yaw with increments of 10° the whole 360° to account for wind coming from all directions. Two geometries were tested for the tower members, one with a circular cross-section which was smaller than scale and another with a square cross-section in correct scale. There was noticeable change in both global forces and moments. Blockage corrections caused by wall interference were researched from different sources and reviewed, and it was apparent that it is still an area with lots of uncertainty. Consensus was that and area ratio of maximum 0.10 should be abided in any case and that the simplified method of Pope is widely used. An atmospheric boundary layer was simulated at NTNU using trial-and-error and the validity of this was confirmed by comparing experimental data with theoretical data regarding the velocity profile, turbulence intensity and energy spectrum. For the experiments of surface roughness on an individual circular cylinder and the corresponding change in drag, a simple three-component balance was used. The cylinder represents the platform legs. Two types of surface roughness were tested, first a plain wooden surface and then with a layer of coarse sand applied to the whole surface. It was seen that the rougher surface provoked an earlier transition to a turbulent boundary layer, causing an earlier drop in drag which is a better fit to estimated full-scale characteristics.Finally, the element that contributes most to the inaccuracy of the experiments is shown to be the difficulty of geometric similarity. Further investigation is needed.
17
Crawley, Damian M. "A wind-tunnel investigation of drag partition." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ55665.pdf.
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Harvey, Scott A. "Low-speed wind tunnel flow quality determination." Thesis, Monterey, California. Naval Postgraduate School, 2011. http://hdl.handle.net/10945/5584.
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Approved for public release; distribution is unlimited.lected points. Incorporated instrumentation includes pressure transducers attached to a pitot-static tube, wall static pressure taps, and a pressure rake; a hotwire anemometry system, and a linear traverse system. These were integrated with a data acquisition (DAQ) processor with analog to digital conversion and digital I/O boards, and controlled using in-house developed LabVIEW software. Testing showed a maximum axial velocity of 38 m/s, which is 84% of the tunnel?s rated speed. The 2-D flow uniformity was within ±7% by pressure rake, and ±3% with a turbulence intensity ?0.11% at full speed using a CTA, affirming the tunnel?s viability as a demonstration platform. Spectral density plots in the boundary layer exhibit typical behavior of fully developed equilibrium turbulent flow with an intertial sub-range present. Future testing of a flat-plate wake for drag modification is planned.
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Roberts, E. C. "Energy simulation of climatic wind tunnel plant." Thesis, Loughborough University, 2000. https://dspace.lboro.ac.uk/2134/7250.
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The Climatic Wind Tunnel (CWT) is a facility used by the motor industry to test vehicles under climatic extremes without the need for expensive overseas test programs. This work focuses on the application of computer simulation to the Heating Ventilation and Air Conditioning (HVAC) plant that makes up a CWT facility. The objective being to reduce its operational costs through the identification of energy saving operational strategies. When in operation the CWT has a peak power consumption of 3MW. The implementation of any measures that would reduce this peak load would give rise to considerable savings in the operating costs of the facility. Computer simulation is an accepted technique for the study of systems operating under varying load conditions. Simulation allows rapid analysis of different strategies for operating plant and the effectiveness of achieving the desired effect without compromising the buildings performance. Models for the components of the CWT have been developed and coded in Neutral Model Format. These models have then been linked together in a modular simulation environment to give a model of the complete plant. The CWT plant naturally decomposesin to four major subsystems these being the test chamber, the soakroom, air make-up and refrigeration system. Models of all the primary and secondary HVAC plant are described as is how they constitute the systems that make up the CWT. Validation tests for individual components as well as for the systems have been carried out. To illustrate the potential of the application of computer simulation into finding improved modes of operation that would reduce the energy consumption of the facility, four studies have been carried out. The studies involve the possibility of scheduling the operation of condenser fans as a function of refrigeration load and outside ambient temperature, methods for the pre-test conditioning of a vehicle, a reduction in the secondary refrigerant flow temperature and an increase in the thickness of the insulated panels from which the facility is constructed. The studies carried out showed that there was potential for moderate energy savings to be made in the operation of the facility and that extended simulation runs would allow for the in-depth assessment of a large range of possible modes of plant operation in order to identify the areas where the greatest savings are possible.
20
Lyu, Zhipeng. "Aerodynamic Wind Tunnel in Passenger Car Application." Thesis, KTH, Mekanik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-203971.
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The thesis aims to provide an evaluation on the Volvo 1/5th scaled wind tunnel regarding its potentials and capabilities in aerodynamic study. The flow quality in the test section was evaluated. The experiments were performed included measurements of airspeed stability, tunnel-wall boundary layer profile and horizontal buoyancy. A numerical model was developed to predict the boundary layer thickness on the test floor. Repeatability tests were also conducted to establish the appropriate operating regime.A correlation study between the 1/5th scaled wind tunnel (MWT) and full scale wind tunnel (PVT) was performed using steady force and unsteady pressure measurements. The Volvo Aero 2020 concept car was selected to be the test model.The Reynolds effect and the tunnel-wall boundary layer interference were identified in the steady force measurements. Unsteady near-wake phenomena such as wake pumping and wake flapping were discussed in the unsteady base pressure measurements.
21
Hurst, Daryl John. "Wind tunnel experiments in fractal induced turbulence." Thesis, Imperial College London, 2007. http://hdl.handle.net/10044/1/7991.
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Inghels, Pieter. "Wind tunnel blockage corrections forwind turbine measurements." Thesis, KTH, Mekanik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-202632.
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Wind-tunnel measurements are an important step during the windturbinedesign process. The goal of wind-tunnel tests is to estimate theoperational performance of the wind turbine, for example by measuringthe power and thrust coecients. Depending on the sizes of both thewind turbine and the test section, the eect of blockage can be substantial.Correction schemes for the power and thrust coecients havebeen proposed in the literature, but for high blockage and highly loadedrotors these correction schemes become less accurate.A new method is proposed here to calculate the eect a cylindricalwind-tunnel test section has on the performance of the wind turbine.The wind turbine is modeled with a simplied vortex model. Usingvortices of constant circulation to model the wake vortices, the performancecharacteristics are estimated. The test section is modeled witha panel method, adapted for this specic situation. It uses irrotationalaxisymmetric source panels to enforce the solid-wall boundary condition.Combining both models in an iterative scheme allows for thesimulation of the eect of the presence of the test-section walls on windturbines performace.Based on the proposed wind-tunnel model, a more general empirical correlationscheme is proposed to estimate the performance characteristicsof a wind turbine operating under unconned conditions by correctingthe performance measured in the conned wind-tunnel conguration.The proposed correction scheme performs better than the existing correctionschemes, including cases with high blockage and highly loadedrotors.
23
Al-Qahtani, Turki Haif. "An improved design of wind towers for wind induced natural ventilation." Thesis, University of Bath, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323566.
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Huff, Michael R. "A LabVIEW- based wind tunnel data acquisition system." Thesis, Monterey, California. Naval Postgraduate School, 1998. http://hdl.handle.net/10945/8605.
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Approved for public release; distribution is unlimitedThe NPS Aerolab Low Speed Wind Tunnel located in Halligan Hall of the Navy Postgraduate School has been in operation since 1953. Although the tunnel is well maintained, its data acquisition system has not kept pace with modem technology. An effective but affordable solution for acquiring data was needed. It was determined that a software package known as LabVIEW would provide a low cost, data acquisition solution that will enhance the capabilities of the wind tunnel, while at the same time making it more user friendly to faculty and students. The focus of this thesis is the design of a VI that will collect and plot force and moment data from a six component strain gauge balance and yield real time, non-dimensional, force and oment coefficients in six degrees of freedom. Wind tunnel tests consisting of angle-of-attack sweeps in the NPS aerolab low-speed wind tunnel were conducted t6 verify (IiD)Isp optimized, M=6, conical-flow waverider data obtained in 1994 using a different data acquisition system. Results of current testing substantiate the LabVIEW code and the validity of the 1994 test data. Analysis of the current wind tunnel test data resolved pitching moment concerns related to the 1994 data.
25
Sheng, Wanan. "CFD simulations in support of wind tunnel testing." Thesis, University of Glasgow, 2003. http://theses.gla.ac.uk/5393/.
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CFD and wind tunnel simulations are complementary due to their inherent limitations. Wind tunnel tests apply to any hypothesis, but are limited by the tunnel wall interference/blockage, the model details, and even the distortion of the model. CFD are not limited in any of these ways, but limited in speed and memory and the lack of determinate set of equations. Theoretically, CFD can provide an assessment of any problem in fluid dynamics (Direct Numerical Simulation), but the requirements of speed and memory are far from being met presently, or even in the foreseeable future. Of necessity, present CFD applications, however, employ a turbulence model, which limits its application due to the problems in accuracy and reliability. Given the power of CFD however, the work contained herein makes use of the advantages of CFD and also the wind tunnel, to form a powerful facility for aerodynamic test, i.e., CFD was used to complement and enhance the wind tunnel test, so producing an integrated test facility. A very important aspect in this work is that CFD was used to investigate the blockage correction for wind tunnel tests. By using CFD, the blockage correction could be made directly, in terms of representing the test model and tunnel walls in high fidelity. Meanwhile, the effect of support system on the test model was also investigated by CFD. The numerical results showed significant effect of the strut on the test model in the Argyll Wind Tunnel (Glasgow University), and an interesting result showed that different positions of support system had different effects. This research aimed to utilise CFD to support wind tunnel testing, and its ultimate purpose is to form a powerful facility for aerodynamic test by combining CFD and wind tunnel. The contributions are summarised as follows: The calibrations of wind tunnel by CFD simulations; A proposed improvement for moving belt system by CFD tools; Blockage correction of wind tunnel by CFD method; and The confirmation of CFD results by wind tunnel model test.
26
Persson, Tobias. "Wind Tunnel Effects on Truck Aerodynamica and Soiling." Thesis, KTH, Mekanik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-203972.
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27
Abudaram, Yaakov Jack. "Wind tunnel testing of load-alleviating membrane wings." [Gainesville, Fla.] : University of Florida, 2009. http://purl.fcla.edu/fcla/etd/UFE0041340.
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28
Noor, Izham Muhammad Ibrahim Afif. "Wind tunnel project for teaching and researching purposes." Thesis, Noor Izham, Muhammad Ibrahim Afif (2017) Wind tunnel project for teaching and researching purposes. Honours thesis, Murdoch University, 2017. https://researchrepository.murdoch.edu.au/id/eprint/41914/.
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This project is concerned with the modelling and redesign of a small wind tunnel system. In the beginning of the project, a used wind tunnel is acquired by the Murdoch University from a company. The wind tunnel is expected to be used for the teaching purposes and it is also anticipated that the wind tunnel system will be used for research. First, an early research and literature review is carried out to obtain knowledge of the wind tunnel and the working principle and equations involved. This research helps to develop a basic understanding on the wind tunnel system and the required specification of the wind tunnel, which requires the wind speed of at least 20m/s. Therefore, an initial study is carry out to investigate and analyse the functionality and the limitations of the existing wind tunnel. The analysis centres around the study to determine whether the existing wind tunnel can be used as it is, or does it require any changes to improve the existing wind tunnel system. Based on the analysis, necessary modelling and redesigns are proposed to get the wind tunnel to achieve its aim. The modelling consists of calculation that are based from the equation acquire from the literature review. Two designs are used in the modelling which is the presented in the thesis and the findings on the modelling are discussed to decide which is the best design to achieve the required wind speed.
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Zhang, Haoran. "Wind tunnel project for teaching and researching purposes." Thesis, Zhang, Haoran (2019) Wind tunnel project for teaching and researching purposes. Honours thesis, Murdoch University, 2019. https://researchrepository.murdoch.edu.au/id/eprint/52714/.
Full textAbstract:
Wind tunnels are test devices used in aerodynamic experiments to understand the effects of air moving through solid objects. Wind tunnels are often used to provide a steady and controlled flow of wind to replace natural winds and to test new models of spacecraft, aircraft and vehicles, and some wind tunnels have enough room to inspect full-size cars.
A small wind tunnel system has been acquired and requires re-design and testing. These works follow on the ENG470 work by Mr Ibrahim Noor Izham, who undertook the initial study that analysed the functionality and limitations of the existing wind tunnel. However, the conclusion of the works shows the current wind tunnel does not have the capability to meet the requirements of Murdoch University.
Therefore, this project aims to design and construct a new open return wind tunnel system for Murdoch University, which has been designed to achieve 20m / s in the test section with expected low turbulence intensity level. Making it available for Murdoch University research and education purposes, for example, research particular emission from biochar-amended soil, low-speed aerodynamics experiments (ENG 339: Wind and Hydro Power Systems: testing aerofoil and wind turbine models). In order to implement these goals, a very detail design was carried on using theoretical modelling and CFD simulations. Moreover, flow stabilization and control are also performed by using a honeycomb and screens; all of these are optimized to produce low turbulence levels in the test section. Furthermore, the axial fan with a VFD for this wind tunnel project was delivered at the end of March 2019, to assist the subsequent wind tunnel project, an experiment was conducted on 25th May 2019 to study the relationship between wind flow speed generated by the axial fan with different fan speed in RPM.
The report has addressed the dimension of the new wind tunnel design by theoretical modelling method. Base on this dimension of the wind tunnel design, an AutoCAD modelling and a CFD simulation is conducted to investigate the turbulence intensity level in the test section. The results show that when the wind tunnel is operated at a wind speed of 20 m / s, the turbulence intensity of the test section is less than 3%. The fan test results show that the maximum wind speed produced by the axial fan is 12.97 m / s, which is much lower than the expected speed of the fan section of 15.405 m / s. The reason is that the vibrations of the fan test structure affect the wind speed measurement of the Pitot tube. In addition, after completing the construction of the entire wind tunnel, the contraction cone will accelerate the flow through the wind tunnel to meet the expected speed.
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BACCHINI, ALESSANDRO. "Electric VTOL preliminary design and wind tunnel tests." Doctoral thesis, Politecnico di Torino, 2020. http://hdl.handle.net/11583/2847140.
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Saddington, Alistair J. "Mutual Interference Between Jets and Intakes in STOVL Aircraft." Thesis, Department of Aerospace, Power and Sensors, 2009. http://hdl.handle.net/1826/3895.
Full textAbstract:
During wind tunnel testing of jet-lift, short take-off and vertical landing (STOVL)
aircraft it is usual to simulate the jet efflux but not the intake flows. The intakes,
which are commonly faired over or are unpowered, are generally tested in separate
wind tunnel experiments. The forces acting on the wind tunnel model are determined
by the linear addition of the forces obtained from the two separate tests.
There is some doubt as to whether this is a valid approach.
A systematic experimental investigation was, therefore, conducted to determine the
magnitude of any jet/intake interference effects on a generic jet-lift STOVL aircraft
in transitional flight, out of ground effect. Comparisons made between separate and
simultaneous jet and intake testing concluded that a mutual jet/intake interference
effect does exist. The existence of this interference means that the aerodynamic wing
lift loss in transitional flight deduced from isolated jet and intake testing is less than
the lift loss obtained from simultaneous jet and intake testing.
The experimental research was supplemented by some simplified computational
fluid dynamics (CFD) studies of elements of the flow-field about the aircraft using
the k-e turbulence model. The numerical modelling enabled aspects of the flow-field
around the aircraft to be visualised which could not easily be done using the experimental
apparatus.
It is a requirement of the Eng]) programme that part of this thesis must address a
management topic linked to the research. In this case the management aspects of
wind tunnel project work were examined. A scenario was developed which established
a requirement for a large-scale, low-speed wind tunnel with a Reynolds number
capability of 20 million. A study was performed on the decision-making process
and investment appraisal methods used in the procurement of such a wind tunnel.
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Kong, Lingzhe. "Experimental investigation of the tolerant wind tunnel for unsteady airfoil motion testing." Thesis, University of British Columbia, 1991. http://hdl.handle.net/2429/29992.
Full textAbstract:
Previously, the concept of the tolerant wind tunnel, developed in the Department of Mechanical Engineering, U. B. C., was tested only for stationary models. In the present study, the concept is investigated for unsteady airfoil motion. The new wind tunnel test section, using the opposite effects of solid and open boundaries, is a new approach to reduce wall blockage effects. Consisting of vertical airfoil slats uniformly spaced on both side walls in the test section, it is designed to produce a nearly free-air test environment for the test model, which leads to negligible or small corrections to the experimental results. The performance of this wind tunnel for unsteady model testing is examined experimentally
with a two-dimensional NACA 0015 airfoil in a simple plunging sinusoidal motion. The airfoil is mounted vertically in the center plane of the test section between solid ceiling and floor. An oscillating table is designed to give the airfoil an accurate plunging sinusoidal motion. A full range of open area ratio is tested by varying the number
of slats mounted inside the side walls. Pressure distribution along the airfoil surface and displacement of the airfoil are measured as functions of time by a data acquisition system designed for this research. Lift and moment are obtained by integration of the pressure distribution at every time increment.
Using a numerical model based on the singularity distribution method, the free air case results for a NACA 0015 airfoil in the same unsteady motion are obtained. Comparison with the linear theory results by Sears¹ are discussed. Comparing with the numerical and the linear theory results, the experimental investigation shows that the new test section produces low-correction data.Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate
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Cusick, A. H. "Investigation of the effects of increased sophistication of simulation of the atmospheric wind in wind tunnels." Thesis, Open University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382907.
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Crede, Erin Dawne. "Aerodynamics and Acoustics of the Virginia Tech Stability Tunnel Anechoic System." Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/34479.
Full textAbstract:
The acoustic treatment and calibration of a new anechoic system for the Virginia Tech Stability Wind Tunnel has been performed. This novel design utilizes Kevlar cloth to provide a stable flow boundary, which eliminates the need for a free jet and jet catcher. To test this concept a series of measurements were performed both to validate the reduction in overall test section noise levels and to ascertain the effect of these modifications on the test section aerodynamics.
An extensive program of experiments has been conducted to examine the performance of this new hardware under a range of conditions. These include baseline experiments that reveal the aerodynamic and aeroacoustic performance of the tunnel in its original configuration, treatment of the tunnel circuit with validation of in-flow noise reduction, wind tunnel tests to examine the effect of the test section acoustic treatment, and measurements of the aerodynamic and aeroacoustic characteristics of a NACA 0012 airfoil model over a range of angles of attack and Reynolds numbers.
These measurements show that acoustically treating the walls of the circuit both upstream and downstream of the test section, as well as the fan, result in an overall reduction of 5 dB depending on frequency, of the in-flow noise level. These measurements also show that the complete system provides a reduction of between 15 to 20dB depending on frequency, in the in-flow background noise level. Measurements taken both within the test section and in the adjacent chambers also show that large Kevlar windows can be used to quietly and stably contain the flow, eliminating the need for an open-jet and jet catcher system, as well as overall noise levels competitive with many other facilities. Measurements on several airfoils at various angles of attack and Reynolds number show that the interference correction for the fully anechoic configuration is approximately -22% for model with a chord length equal to half the test section height.
Aerodynamic measurements with the NACA 0012 airfoil show its lift, drag and boundary layer characteristics at high Reynolds numbers are consistent with theoretical expectations. Measurements of the window deflection as well as examination of flow transpiration through the Kevlar windows were accomplished, both with and without the NACA 0012 model. These measurements, along with the interference correction data, confirm that the Kevlar windows are a stable flow boundary.Master of Science
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Stoker, Robert W. "A method to separate wind-tunnel background noise and wind noise from interior measurements." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/12032.
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Yatsco, Michael P. "Numerical Analysis and Wind Tunnel Validation of Wind Deflectors for Rooftop Solar Panel Racks." Youngstown State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1310680204.
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Reinap, Ausra. "Aerosol deposition to coastal forests: a wind tunnel approach." Doctoral thesis, Linnéuniversitetet, Institutionen för naturvetenskap, NV, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-11999.
Full textAbstract:
Aerodynamically rough surfaces of forests provide for efficient air/ canopy exchange of mass, heat and momentum. In that context, the effects of forest edges come into focus, and therefore, coastal-zone forests constitute aparticular concern. Aerosol-sink modelling is of importance to the global-scalecontext, because sink strengths influence the concentration of aerosol particles in the atmosphere, and that concentration, in turn, influences climate. Dry deposition models are insufficient due to a lack of semi-empirical data and because of difficulties in parameterization of the efficiency (E) with which leaves capture aerosols. Quantifications of such parameters promote possibilities for modelling aerosol-sink processes within various canopy layers. This thesis focuses on studies of sea-salt aerosol dry deposition within models of oak canopies exposed to artificially generated aerosols in a wind tunnel. The overall goal is to advance the understanding of deposition processes in forest ecosystems. Aims are to determine capture efficiencies and deposition velocities (Vd) for oak (Quercus robur L.), to investigate E and Vd dependence on aerosol particle size, wind velocity and vegetation structural elements such as Leaf Area Index (LAI), to explore edge effects on deposition, to relate my results to natural situations in the field, and to address modelling applications. This thesis is a result of five studies. The first study is based on developing awind tunnel approach with a main focus on establishing reference conditions.The next step is to quantify E and provide estimates of how E, with respect toa well defined mass-vs-particle-size distribution, varies with wind speed. To that end, a special wash-off technique is developed. Finally, edge effects ondeposition processes are investigated. Results demonstrate that forest ecosystems would experience substantially increased deposition at edges. The findings suggest that field measurements of deposition in the interior of a forest “island” in an otherwise open landscape would underestimate the deposition to the entire forest. Results clearly indicate needs for further research on the effects of LAI on capture efficiency and deposition velocity. The obtained capture efficiencies can be translated into deposition velocities for trees with a specific leaf area. An increase of Vd with increasing wind speed is found, and is consistent with other studies. Results confirm advantages of the wind tunnel approach, including its ability to enable experiments under controlled conditions. However, several problems require that explicit sub-models be developed of wind-speed dependent effects on leaf posture in the aerosol flow field and that gradients in relative humidity close to leaf surfaces need further attention. The results also propose needs for a range of further experimental investigations regarding aerosol deposition across the complete sea-to-land aerodynamic transition.
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Kounenis, Charalampos. "Effects of wind-tunnel simulation of on-road conditions." Thesis, Durham University, 2018. http://etheses.dur.ac.uk/12970/.
Full textAbstract:
A road vehicle experiences different conditions on the road than the ones in the development environment such as wind-tunnel and CFD. In this work, on-road unsteadiness together with moving ground and rotating wheels were studied as the on-road environment. These conditions were then investigated using full-size and model-scaled vehicles, looking their impact on aerodynamic force coefficients, rear wake structures and in particular aeroacoustics. Reproducing the effects of unsteady wind using a Turbulence Generation System(TGS) in the wind-tunnel showed that while the on-road yaw angle is varied, the time-averaged cabin noise will be increased but this increment is small. A more important effect of time-varying onset flow is the modulation of wind noise. The impact of the modulation for an assumed on-road environment was equivalent to an extra 1-2 dB(A) in cabin noise, from the point of view of passenger perception while the increment in time-averaged cabin noise would only be 0.2 dB(A). The lack of ground effect simulation in the wind-tunnel could also result in different flow conditions from those on the road. This work showed that the underbody of the vehicle is very important especially for the passengers at the rear seat, with an influence up to 5 dB(A) particularly for lower frequencies below 1 kHz. Another important observation was that performing aeroacoustic measurements with moving ground would be possible across the spectrum, being able to identify any changes in cabin noise without any significant impact from mechanical noise masking effects. Finally, the importance of unsteadiness to vehicle response was studied using different TGS modes representing the on-road environment intensities and length scales. The front bumper was found to be influenced by unsteadiness at frequencies 1, 2 and 4 Hz, while both waistline and base showed a more quasi-steady behaviour. For the side-glass and A-pillar, the harmonic modes showed unsteady behaviour more pronounced at the leeward side, closer to the mirror wake area where frequencies 1Hz < f < 4Hz, appeared to be key frequencies with respect to unsteadiness.
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Pattinson, John. "Development and evaluation of a wind tunnel manoeuvre rig." Thesis, University of Bristol, 2010. http://hdl.handle.net/1983/6a7d4b89-aada-4e48-8d12-92cadeac3f2a.
Full textAbstract:
A novel wind tunnel rig, which can be used to collect data from high incidence, large amplitude manoeuvres is presented. The "manoeuvre rig" is a horizontal-pendulum type rig that is capable of large amplitude motions in up to five degrees of freedom. The rig consists of. two gimbals, an arm to provide an element of translation to the model centre of gravity, an aerodynamic compensation device, and a scale aircraft model. It is remotely controlled allowing largely unhindered motion and the potential for the investigation of feedback control laws. To assess the manoeuvre rig concept, a pilot rig was designed, manufactured and operated. For the tests, an existing approximate-scale model of the BAe Hawk aircraft is used. Mathematical models of the rig components and their dynamics are developed, with additions that account for friction. Small amplitude manoeuvres, typical of conventional testing, are performed. Mathematical models, describing the longitudinal aerodynamics of the Hawk, are fitted to this data using parameter estimation methods. Excellent results are achieved in the one degree-of-freedom pitch configuration. In two degrees-of-freedom pitch and heave, the results are not as good and the reasons for this are discussed. The Hawk model exhibits significant nonlinear behaviour at high angles of attack. This is thought to be related to dynamic stall and a suitable mathematical model is developed. Continuation and bifurcation analysis is used to analyse this model and fit it to experimental data. Qualitative agreement between the model and the data is achieved and influence of friction on the rig dynamics is discussed. The rig's capabilities are further evaluated by the demonstration of large amplitude, three degree of freedom (roll, pitch and yaw) tests, velocity vector rolls (roll and pitch) and four degree (roll, pitch, yaw and sway) of freedom snake-like motions. The manoeuvre rig is shown to be suitable for the extraction of longitudinal aerodynamic models. It is capable of generating small- and large-amplitude unsteady motions so that aircraft responses can be demonstrated and studied. As such, the rig shows promise for aerodynamic model extraction for nonlinear dynamics and departure
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Zorrilla, Martínez Rubén. "Towards the virtual wind tunnel for civil engineering applications." Doctoral thesis, Universitat Politècnica de Catalunya, 2020. http://hdl.handle.net/10803/671768.
Full textAbstract:
This thesis develops a numerical tool (the Virtual Wind Tunnel, VWT) for the resolution of problems involving fluid flow around structures. Due to the limitations that traditional methods may have in this context, the VWT is based on the use of fixed mesh technologies (CutFEM-type) combined with an implicit representation of the embedded bodies.
One of the main contributions of the thesis is the use of such fixed mesh methods to solve lightweight thin-walled structures problems. Hence, two embedded formulations capable of representing the flow around bodies with and without internal volume are proposed. The first one results in a simpler implementation and lower computational effort but can only represent a slip behavior of the wall. The second one gets rid of such limitation by including a Nitsche imposition of the Navier-slip condition, thus allowing modelling any wall behavior as a wall law would do.
The applicability range of the VWT includes the fluid–structure interaction problem (FSI). To that purpose an improvement for the boundary condition imposition of the FM-ALE algorithm mesh motion problem is also proposed. Moreover, the implementation, which has been conceived to be easily extended to any other coupled problem, is also treated.
The validation of the technologies within the VWT includes multiple theoretical test cases as well as feasible industrial applications. Among these, the FSI analysis of a 4-point tent during a strong wind episode deserves to be highlighted as it showcases the achievement of the initial objective of the thesis.En esta tesis se desarrolla una herramienta numérica (el Virtual Wind Tunnel, VWT) para la resolución de problemas que involucran el flujo de un fluido alrededor de una estructura. Debido a las limitaciones que los métodos tradicionales pueden tener en este contexto, el VWT se basa en el empleo de técnicas de malla fija (tipo CutFEM) combinadas con una descripción implícita de los cuerpos embebidos. Una de las principales contribuciones de la tesis es el empleo de dichos métodos de malla fija para resolver problemas de estructuras ligeras de pared delgada. Así pues, se proponen dos formulaciones embebidas capaces de representar el flujo alrededor de un cuerpo con o sin volumen interno. La primera de ellas resulta en una implementación más sencilla así como en un menor coste computacional pero únicamente puede reprentar un comportamiento deslizante de la pared. La segunda elimina esta limitación incluyendo una imposición mediante el método de Nitsche de la condición de Navier-slip, permitiendo así modelar cualquier comportamiento del mismo modo que lo haría una ley de pared. El rango de aplicabilidad del VWT incluye el problema de interacción fluido¿estructura (FSI). A tal propósito se plantea una mejora para la imposición de las condiciones de contorno del problema de movimiento de la malla del algoritmo FM-ALE. Asimismo, también se hace especial hincapié en la implementación, que ha sido concebida para ser fácilmente extensible a cualquier otro problema acoplado. La validación de las tecnologías implementadas en el VWT incluyen múltiples casos teóricos así como posibles aplicaciones industriales. Entre éstas se destaca el análisis FSI de una 4-point tent durante un episodio de viento severo ya que demuestra la consecución del objetivo inicial de la tesis.
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Frison, Giovanni. "Aeroelastic and aerodynamic wind tunnel tests for tall buildings." Doctoral thesis, Università degli studi di Padova, 2019. http://hdl.handle.net/11577/3423186.
Full textAbstract:
Starting from the consolidated concept of aerodynamic model, a benchmark is proposed to further asses an extend its capability of correctly identify the dynamic response of a tall building, devoting particular attention to the contribution of higher-order modes and the possible presence of aerodynamic damping. Being the extrema ratio in terms of accuracy and reliability, a full-aeroelastic model of a tall building is presented as the subject of comparison. The complexity involved in the dynamic wind-tunnel scaling led to the definition of a novel semi-automatized procedure. Based on the author’s experience, developed during the project, each step comes with practical advice, often challenging to find in the scientific literature, and food for thought on the worthiness of design-oriented aeroelastic modeling approach. The design, construction, identification, and validation of a 1:360-scale, a four-level lumped-mass aeroelastic model of the well-known Caarc standard tall building, is presented. Differently to the numerous previous research involving the Caarc building, here it is disclosed in a new guise, featuring torsional and second-order modes, enhancing the challenge for the aerodynamic model test. An extensive experimental campaign is performed at the CRIACIV boundary layer wind tunnel. Tests are performed in turbulent flow for a wide range of velocities and varying the structural damping to be able to address the results for different design criteria. Although the aerodynamic model is generally found to provide useful insight in the building response, the presence of aerodynamic damping and second-order modes are found to be relevant both in terms of base moments and acceleration. From a design perspective, even for "not exceptional" tall buildings, such as the Caarc, the aerodynamic model seems a valid option for early design stages, while the adoption of an aeroelastic model might be a valuable solution in the refinement of loads or serviceability criteria.
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Westin, Michelle Fernandino. "Aeroelastic modeling and experimental analysis of a flexible wing for wind tunnel flutter test." Instituto Tecnológico de Aeronáutica, 2010. http://www.bd.bibl.ita.br/tde_busca/arquivo.php?codArquivo=1121.
Full textAbstract:
The objective of this work is to investigate the flutter phenomena experimentally, which will unify high aspect ratio wings design for wind tunnel flutter tests (Dowell and Tang, 2002), cheaper aeroelastic models construction and a procedure used by Sheta, Harrand, Thompson and Strganac (2002) to identify the flutter onset power spectral density versus the frequency. Initially, an experimental model developed by Dowell and Tang (2002) has been considered as a baseline model and, from this point, two new models with different wing configurations were determined, including the slender body at wing's tip, which is the idea extracted from Dowell's work, so that the torsion and bending modes are coupled (torsional moment of inertia reduction). The aeroelastic model can be divided into two parts: First, the wings structural dynamic models are computed using the finite element method implements in NASTRAN solver. sequently, ZAERO software is employed to compute the aeroelastic model. Unsteady aerodynamic loading is computed through a lifting surface interference method known as ZONA 6. The wing models defined as test beds will be constructed and tested in different wind tunnels, including open and closed tests section types. The power spectral density approach might be employed as a way to identify flutter. The output signal from an accelerometer placed in the wing structure allows, through its power spectral density computation, the identification of flutter onset condition and the corresponding undisturbed flow speed. The PSD function increase means flow energy extraction, a condition to have flutter. Experimental flutter speeds are close to the theoretically computed ones by ZAERO. From these observations, it is possible to validate the aeroelastic theoretical model in a small disturbance context. After flutter onset , the limit cycle oscillations are observed, fed by freestream energy extraction. The aeroelastic models under investigation in this research are excellent models for nonlinear aeroelastic phenomena behavior study.
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Hameury, Michel. "Development of the tolerant wind tunnel for bluff body testing." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/27311.
Full textAbstract:
In conventional wind tunnels the solid-wall or open-jet test section imposes on the flow field around the test model new boundary conditions absent in free air. Unless a small model is used, the solid-wall test section generally increases the loadings on the model while the open-jet boundary decreases the loadings compared to the unconfined case.
However, the development of a low wall-interference test section and its successful demonstration would allow the testing of relatively large models without the application of often uncertain correction formulae.
The Tolerant wind tunnel, which makes use of the opposite effects of solid and open boundaries, is a transversely slatted-wall test section designed to produce at an optimal wall open-area ratio (OAR) low-correction data for a wide variety of model shapes and sizes. Initially intended for low-speed airfoil testing, its use is theoretically and experimentally investigated here in connection with bluff body testing.
A simple mathematical model based on two-dimensional potential flow theory and solved with the help of a vortex surface-singularity technique is used to estimate the best wall configuration. The theory predicts an optimum OAR of about 0.45 at which pressure distributions on flat plate and circular cylinder models of blockage ratios up to 33.3 % would differ from the free-air values by not more than 1 %.
On the other hand, experiments performed with flat plate, circular cylinder and circular-cylinder-with-splitter-plate models indicate the existence of an optimum configuration around OAR = 0.6. The experiments also show a maximum allowable blockage in the Tolerant wind tunnel to be equivalent to the blockage created by a 33.3 %-blockage-ratio flat plate model.Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate
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Jones, Gregory Stephen. "The measurement of wind tunnel flow quality at transonic speeds." Diss., Virginia Tech, 1991. http://hdl.handle.net/10919/39109.
Full textAbstract:
The measurement of wind tunnel flow quality for the transonic flow regime has been plagued by the inability to interpret complex unsteady flow field information obtained in the free stream. Traditionally hot wire anemometry and fluctuating pressure techniques have been used to quantify the unsteady characteristics of a wind tunnel. This research focuses on the application of these devices to the transonic flow regime.
Utilizing hot wire anemometry, one can decompose the unsteady flow field with a three sensor technique, to obtain fluctuations associated with the velocity, density, and total temperature. Implementing thermodynamic and kinematic equations, new methods for expanding the measured velocity, density, and total temperature fluctuations to obtain additional fluctuations are investigated. The derived static pressure fluctuations are compared to the static pressure fluctuations obtained with a conventional fluctuating static pressure probe. The results of this comparison are good, which implies that the individual velocity, density, and total temperature components are time accurate.
In the process of obtaining a high quality fluctuating flow field information, it was necessary to evaluate the calibration of the hot wire sensors. A direct calibration approach was compared to a conventional non-dimensional technique. These two calibration techniques should have resulted in the same hot wire sensitivities. There were significant differences in the hot wire sensitivities as obtained from the two approaches. The direct approach was determined to have less errors due to the added heat transfer information required of the indirect approach. Both calibration techniques demonstrated that the velocity and density sensitivities were in general not equal. This suggests that the velocity and density information cannot be combined to form a mass flow. A comparison of several hot wire techniques was included to highlight the errors obtained when assuming that these sensitivities are the same.
An evaluation of the free stream flow quality associated with a Laminar Flow Control experiment was carried out in the Langley Research Center 8-Foot Transonic Pressure Tunnel (8' TPT). The facility was modified with turbulence manipulators and a liner that provided a flow field around a yawed super-critical airfoil that is conducive to transition research. These devices are evaluated to determine the sources of disturbances associated with the LFC experiment.Ph. D.
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Letchford, C. W. "Pneumatic averaging and its application in wind engineering." Thesis, University of Oxford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233481.
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Styles, Julie M. "A wind tunnel study of the velocity field above a model plant canopy." [Canberra] : CSIRO Land and Water, 1997. http://nla.gov.au/nla.arc-13482.
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Thesis (B.Sc. (Honours)) - Australian National University, 1997.Title from title screen (viewed on May 20, 2002). "A thesis submitted in partial fulfilment of the requirements for the Degree of Bachelor of Science (Honours)"--Title screen. Bibliography: p. 64-66. Available full text via the internet.
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Griffith, Dwaine O. "Turbulence measurements and noise generation in a transonic cryogenic wind tunnel." Thesis, Virginia Tech, 1989. http://hdl.handle.net/10919/45979.
Full textAbstract:
A high-frequency combination probe was used to measure dynamic flow quality in the test section of the NASA Langley 0.3-m Transonic Cryogenic Tunnel. The probe measures fluctuating stagnation (total) temperature and pressure, static pressure, and flow angles in two orthogonal planes. Simultaneous unsteady temperature and pressure measurements were also made in the settling chamber of the tunnel. The data show that the stagnation temperature fluctuations remain constant, and the stagnation pressure fluctuations increase by a factor of two, as the flow accelerates from the settling chamber to the test section. In the test section, the maximum rms value of the normalized fluctuating velocity is 0.7 percent. Correlation coefficients l failed to show vortlcity, entropy, or sound as the dominant mode of turbulence in the tunnel.
At certain tunnel operating conditions, periodic disturbances are seen in the data taken in the test section. A possible cause for the disturbances is found to be acoustic coupling of the test section and plenum chamber via the perforated side walls in the tunnel. The experimental data agree well with the acoustic coupling theory.
Master of Science
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Warsido, Workamaw Paulos. "Reducing Uncertainties in Estimation of Wind Effects on Tall Buildings Using Aerodynamic Wind Tunnel Tests." FIU Digital Commons, 2013. http://digitalcommons.fiu.edu/etd/939.
Full textAbstract:
Tall buildings are wind-sensitive structures and could experience high wind-induced effects. Aerodynamic boundary layer wind tunnel testing has been the most commonly used method for estimating wind effects on tall buildings. Design wind effects on tall buildings are estimated through analytical processing of the data obtained from aerodynamic wind tunnel tests. Even though it is widely agreed that the data obtained from wind tunnel testing is fairly reliable the post-test analytical procedures are still argued to have remarkable uncertainties. This research work attempted to assess the uncertainties occurring at different stages of the post-test analytical procedures in detail and suggest improved techniques for reducing the uncertainties.
Results of the study showed that traditionally used simplifying approximations, particularly in the frequency domain approach, could cause significant uncertainties in estimating aerodynamic wind-induced responses. Based on identified shortcomings, a more accurate dual aerodynamic data analysis framework which works in the frequency and time domains was developed. The comprehensive analysis framework allows estimating modal, resultant and peak values of various wind-induced responses of a tall building more accurately.
Estimating design wind effects on tall buildings also requires synthesizing the wind tunnel data with local climatological data of the study site. A novel copula based approach was developed for accurately synthesizing aerodynamic and climatological data up on investigating the causes of significant uncertainties in currently used synthesizing techniques. Improvement of the new approach over the existing techniques was also illustrated with a case study on a 50 story building.
At last, a practical dynamic optimization approach was suggested for tuning structural properties of tall buildings towards attaining optimum performance against wind loads with less number of design iterations.
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Chen, Yan-Jhih, and 陳彥志. "Wind Tunnel Experiments of Wind-driven Ventilation." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/spc42y.
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碩士國立中央大學
土木工程研究所
96
The wind-driven ventilation for buildings is dependent on the pressure difference between internal and exterior pressure. This study uses theoretical and experimental approaches to investigate wind-driven ventilation. The experiments were carried out in a large scale wind tunnel to study the influences of wind speed, attack angle, size and shape of opening and outdoor flow conditions (steady flow, turbulent flow and gusty flow). Besides, a wind-pressure balance model was developed to calculate the ventilation rate depending on the exterior pressure, opening size and discharge coefficient. The experimental results demonstrate that the wind-pressure balance model can predict ventilation rates of different opening sizes and attack angles in steady flow, but fail to predict the instantaneous ventilation rate in turbulent flow when in the attack angle is 90°. In the gusty flow, the internal pressure has the same fluctuating frequency as the exterior pressure
50
Molina, Andreu Carbó. "Wind tunnel testing of small Vertical-Axis Wind Turbines for urban areas." Doctoral thesis, 2019. http://hdl.handle.net/2158/1179097.
Full textAbstract:
The implementation of small vertical-axis wind turbines (VAWTs) in urban environments is being studied by the scientific community to complement large wind farms in wind energy generation. The technology is, however, far from maturity due to the complexity of urban flows and the lack of knowledge in the field. This thesis focuses on turbulence, one of the main characteristics of urban flows, and its influence on VAWT performance. Its objective is to generate turbulent wind conditions inside a wind tunnel and testing a VAWT to determine how turbulence intensity (Iu) and integral length scale (Lux) affect its operation. The first part of the research was devoted to obtaining highly-turbulent wind profiles in the wind tunnel with the use of different configurations of square grids. Gathering experience from previous studies and literature, a careful study and validation of this technique was done, in order to obtain uniform wind conditions with the adequate values of turbulence intensity and length scales to model the urban flows. Then, a H-Darrieus VAWT prototype was tested under these turbulent conditions in two different wind tunnels (VUB in Belgium, and CRIACIV in Italy). Those campaigns allowed to evaluate the crossed effect of Iu, Lux and Reynolds numbers on the VAWT performance, and quantify the effect of wind tunnel blockage in the measurements. Further tests with the same set-up included the study of the near wake of the VAWT and the aerodynamic characteristics of the individual blades, always focusing on the effect of incoming turbulence. Finally, a short campaign was done at the large VKI L1-B wind tunnel to observe the effect of a shear flow with high levels of Lux (impossible to model in smaller wind tunnels). The tests on the VAWT revealed an important increase of performance for low to moderate Iu values (5-15%) in low chord-based Reynolds numbers (Rec < 100000), while the effect of Lux was negligible. Iu also proved to cause a positive effect by providing faster wake recovery and by mitigating the negative effect of the turbine shaft. The study of the effect of turbulence on the aerodynamic coefficients of different typical VAWT aerofoils showed that turbulence considerably delays the stall in the blades, which was linked the increase of turbine performance. The tests at VKI proved that this positive effect of turbulence is also evident in shear flows. The possibility of testing in three different wind tunnels strengthens the results of this study, which have been already used in combination with CFD simulations, and present good agreement with literature. The findings of this thesis contribute to expand the knowledge of how turbulent flows interact with VAWTs, and provide a useful insight for the optimization and combination of several VAWTs inside urban environments.