Dissertations / Theses on the topic 'Boundary Layer Wind Tunnel (BLWT)'
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Grossir, Guillaume. "Longshot hypersonic wind tunnel flow characterization and boundary layer stability investigations." Doctoral thesis, Universite Libre de Bruxelles, 2015. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209044.
Full textEmphasis is initially placed on the flow characterization of the Longshot wind tunnel where these experiments are performed. Free-stream static pressure diagnostics are implemented in order to complete existing stagnation point pressure and heat flux measurements on a hemispherical probe. An alternative method used to determine accurate free-stream flow conditions is then derived following a rigorous theoretical approach coupled to the VKI Mutation thermo-chemical library. Resulting sensitivities of free-stream quantities to the experimental inputs are determined and the corresponding uncertainties are quantified and discussed. The benefits of this different approach are underlined, revealing the severe weaknesses of traditional methods based on the measurement of reservoir conditions and the following assumptions of an isentropic and adiabatic flow through the nozzle. The operational map of the Longshot wind tunnel is redefined accordingly. The practical limits associated with the onset of nitrogen flow condensation under non-equilibrium conditions are also accounted for.
Boundary layer transition experiments are then performed in this environment with free-stream Mach numbers ranging between 10-12. Instrumentation along the 800mm long conical model includes flush-mounted thermocouples and fast-response pressure sensors. Transition locations on sharp cones compare favorably with engineering correlations. A strong stabilizing effect of nosetip bluntness is reported and no transition reversal regime is observed for Re_RN<120000. Wavelet analysis of wall pressure traces denote the presence of inviscid instabilities belonging to Mack's second mode. An excellent agreement with Linear Stability Theory results is obtained from which the N-factor of the Longshot wind tunnel in these conditions is inferred. A novel Schlieren technique using a short duration laser light source is developed, allowing for high-quality flow visualization of the boundary layer disturbances. Comparisons of these measurement techniques between each other are finally reported, providing a detailed view of the transition process above Mach 10.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished
Clifton, Andrew James. "Wind tunnel investigations of boundary layer conditions before and during snow drift /." Zürich : ETH, 2007. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17165.
Full textBertholds, Alexander. "CFD Simulations of the New University of Sydney Boundary Layer Wind Tunnel." Thesis, Uppsala universitet, Institutionen för teknikvetenskaper, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-166945.
Full textMazur, Zachary Thomas Lyn. "Calibration and Baseline Flow Surveys of a Reconstructed Boundary-Layer Wind Tunnel." Youngstown State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1597422848793191.
Full textWu, Jie [Verfasser]. "Boundary-layer Instability Experiments in a Tandem Nozzle Supersonic Wind Tunnel / Jie Wu." Aachen : Shaker, 2015. http://d-nb.info/106904864X/34.
Full textTirtey, Sandy C. "Characterization of a transitional hypersonic boundary layer in wind tunnel and flight conditions." Doctoral thesis, Universite Libre de Bruxelles, 2009. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210367.
Full textA wide bibliographic review describing the main parameters affecting transition and their coupling is proposed. The most popular roughness-induced transition predictions correlations are presented, insisting on the lack of physics included in these methods and the difficulties encountered in performing ground hypersonic transition experiments representative of real flight characteristics. This bibliographic review shows the importance of a better understanding of the physical phenomenon and of a wider experimental database, including real flight data, for the development of accurate prediction methods.
Based on the above conclusions, a hypersonic experimental test campaign is realized for the characterization of the flow field structure in the vicinity and in the wake of 3D roughness elements. This fundamental flat plate study is associated with numerical simulations for supporting the interpretation of experimental results and thus a better understanding of transition physics. Finally, a model is proposed in agreement with the wind tunnel observations and the bibliographic survey.
The second principal axis of the present study is the development of a hypersonic in-flight roughness-induced transition experiment in the frame of the European EXPERT program. These flight data, together with various wind tunnel measurements are very important for the development of a wide experimental database supporting the elaboration of future transition prediction methods.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished
Blanco, Mark Richard. "Design and Qualification of a Boundary-Layer Wind Tunnel for Modern CFD Validation Experiments." Youngstown State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1559237473563483.
Full textFonti, Elio. "Measurements of aircraft wake vortices in ground proximity within an atmospheric boundary layer wind tunnel." Thesis, Cranfield University, 2010. http://dspace.lib.cranfield.ac.uk/handle/1826/5635.
Full textPetersen, Graciana [Verfasser], and Bernd [Akademischer Betreuer] Leitl. "Wind tunnel modelling of atmospheric boundary layer flow over hills / Graciana Petersen. Betreuer: Bernd Leitl." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2013. http://d-nb.info/1031280405/34.
Full textPetersen, Graciana Verfasser], and Bernd [Akademischer Betreuer] [Leitl. "Wind tunnel modelling of atmospheric boundary layer flow over hills / Graciana Petersen. Betreuer: Bernd Leitl." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2013. http://nbn-resolving.de/urn:nbn:de:gbv:18-60540.
Full textGalbraith, Daniel S. "Computational Fluid Dynamics Investigation into Shock Boundary Layer Interactions in the “Glass Inlet” Wind Tunnel." University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1322053278.
Full textJoseph, Liselle AnnMarie. "Transition Detection for Low Speed Wind Tunnel Testing Using Infrared Thermography." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/78145.
Full textMaster of Science
Horton, Damien. "Development of an Infrared Thermography System to Measure Boundary Layer Transition in a Low Speed Wind Tunnel Testing Environment." DigitalCommons@CalPoly, 2021. https://digitalcommons.calpoly.edu/theses/2287.
Full textHobson-Dupont, Maximillian. "The development of a small scale wind tunnel simulating the atmospheric boundary layer in support of a stochastic wind model." Thesis, San Jose State University, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=1593083.
Full textThere has been much success in atmospheric boundary layer simulation with medium sized closed-circuit wind tunnels with test section dimensions of approximately 1 x 1 m. However, smaller, blower-type wind tunnels are more common in university laboratories due to the lower cost and smaller space requirements. A small size, open flow wind tunnel with a 1 x 1 foot test section was modified to simulate the atmospheric boundary layer with a combination of upstream spires and cubic roughness elements. The primitive spire geometry detailed in the literature was found to yield poor agreement with the power law velocity profile of interest, and a novel iterative algorithm was developed to produce nonlinear spire geometry. The geometry generated by the algorithm was tested in the wind tunnel and found to simulate the desired velocity profile based on a Hellman exponent of 0.20 with a high degree of agreement, having a maximum velocity error of 4%. This confirmed the suitability of small-sized wind tunnels for simulating the atmospheric boundary layer.
James, Ralph William. "The effect of boundary layer blowing in the corner region of a linear compressor cascade wind tunnel." Thesis, This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-05092009-040547/.
Full textMallor, Fermin. "Enabling high-fidelity measurements of turbulent boundary layer flow over wing sections in the MTL wind tunnel." Thesis, KTH, Mekanik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-264842.
Full textEn NACA 4412 vingprofilsmodel av förstärkt glasfiber utformas och installeras enligt Minimum Turbulence Level (MTL) i vindtunnelanläggningen på KTH. Modellen har 65 tryckluftsöppningar, och uppsättningen innehåller två monteringspaneler som är utformade för att möjliggöra mätningar av particle image velocimetry (PIV) and hot wire anemometry (HWA) hos gränsskiktet (som ska utföras i en framtida kampanj). I en första experimentell kampanj utförs tryckskanningar vid tre anfallsvinklar av intresse (5, 10, och 12 grader) samt vid fyra olika Reynolds-nummer (200 000, 400 000, 1 000 000 och 1 640 000). De preliminära resultaten visar god överensstämmelse med DNS- och LES-data, men den effektiva anfallsvinkeln på vingen påverkas av störningar från testsektionen. För att tillhandahålla korrekta flödesförhållanden för framtida kampanjer i testdelen är vägginsatser konstruerade med 2D k-omega SST-simuleringar. Sidoväggarna är strömlinjeformade och den slutliga geometrin korrigeras för att ta hänsyn till gränsiktets tillväxt. Insatserna undviker den tidig separation som sker nära bakkanten vid högre anfallsvinklar (10 och 12 grader), men 2D-simuleringarna misslyckades med att fånga det ovan nämnda anfallsvinkelproblemet som påverkar tryckfördelningarna.
Goliber, Matthew Robert. "Pressure distribution on the roof of a model low-rise building tested in a boundary layer wind tunnel." [Ames, Iowa : Iowa State University], 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1473211.
Full textRoepke, Joshua. "AN EXPERIMENTAL INVESTIGATION OF A GOLDSCHMIED PROPULSOR." DigitalCommons@CalPoly, 2012. https://digitalcommons.calpoly.edu/theses/939.
Full textHussain, Ali. "The Effect of Spanwise Location of an Active Boundary Layer Fence on Swept Wing Performance." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1555516043121521.
Full textEbenhoch, Raphael. "Simplified modeling of wind-farm flows." Thesis, KTH, Strömningsfysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-177309.
Full textDi, Giovanni Antonio [Verfasser], Christian [Akademischer Betreuer] Stemmer, Wolfgang [Gutachter] Schröder, and Christian [Gutachter] Stemmer. "Roughness-Induced Transition in a Hypersonic Capsule Boundary Layer under Wind-Tunnel and Reentry Conditions / Antonio Di Giovanni ; Gutachter: Wolfgang Schröder, Christian Stemmer ; Betreuer: Christian Stemmer." München : Universitätsbibliothek der TU München, 2020. http://d-nb.info/1211725227/34.
Full textWittwer, Adrián Roberto. "Simulação do vento atmosférico e dos processos de dispersão de poluentes em túnel de vento." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2006. http://hdl.handle.net/10183/8684.
Full textThe experimental study of the pollutant dispersion processes allows the analysis of specific problems as well as the evaluation of theoretical models. The costs related to full scale measurements make the experimental studies over reduced scaled models a better research tool. This work has the aim of modeling some kinds of atmospheric winds and related dispersion processes in wind tunnels. The general modeling laws related to the experimental study of pollutants dispersion were followed, including the boundary layer simulation and the emission source. Several experimental models of the turbulent winds in neutral boundary layers were developed and evaluated by using very low wind velocities, allowing the fulfillment of the similitude laws of the dispersion process. The simulations include turbulent winds over homogeneous terrains at different scales. Literature data were used in the experimental evaluation as well as direct comparisons with field results for the atmosphere under neutral stability conditions. Also, more complex turbulent flows were studied in the close proximities of a simple building model in a non homogeneous surrounding. For the atmospheric diffusion studies, it was decided to model local dispersion situations. A single, punctual type of emission source was modeled, representing the conditions at a low height chimney and allowing the modification of the plume buoyancy conditions. The analysis of the dispersion process and concentrations was performed under several configurations including the isolated source emission in a homogeneous flow, the consideration of the wake effects close to a building model, and finally of a non homogeneous urban terrain. The mean and fluctuating components of the plume concentration were obtained. These results allowed the characterization of the concentration fields. From the probability and spectral density functions it was possible to analyze the intermittence of the concentration field. Comparisons with literature results and with theoretical models complement the study. Special care is taken in the analysis of the fluctuations of the concentration and in the intermittence of the dispersion processes, due to its importance to the development of theoretical models as well as the lack of experimental information in the open literature.
Wisda, David Martin. "Noise from a Rotor Ingesting Inhomogeneous Turbulence." Thesis, Virginia Tech, 2015. http://hdl.handle.net/10919/52986.
Full textMaster of Science
Mattuella, Jussara Maria Leite. "Avaliação em túnel de vento do comportamento da camada limite atmosférica em terrenos complexos." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2012. http://hdl.handle.net/10183/85643.
Full textThe structure of the wind varies with the characteristics of the terrain and roughness land surface, slowing its intensity proportionally according to the surrounding terrain, which determines the onset of boundary layer (ABL). The characteristics of the flow over and around topographic features such as hills are of great interest in many applications, especially those related to wind engineering. From an experimental simulation of the boundary layer wind tunnel, it is possible to parameterize the effects of wind over complex terrain (MILLER, 1995). The definition of variables, such as the profile of wind speed, the turbulence intensity, the topographic effects on wind speed are key elements in structural calculations for buildings situated around the area. This research focuses on the investigation of the ABL complex terrain conditions, analyzing the structure of turbulent flow and characterization of separation and reattachment of the flow. Experimental simulations were developed in the wind tunnel of the atmospheric boundary layer Prof. Joaquim Blessmann, Federal University of Rio Grande do Sul in nine models of hills, four symmetrical two-dimensional, four- symmetrical threedimensional and one asymmetrical, all considering two types of terrain, category I - plan and Category III-IV- moderately rough. The surface of the asymmetric model was measured in nine profiles ploted on the main radial of the hill, with twenty heights each, and the other models were examined at top of the hill. The measurements were performed with a system of hot wire anemometry to measure the wind velocity and intensity of turbulence. The identification of the data obtained in the wind tunnel were confronted with empirical expressions for the same points, in order to establish the correlations between patterns and among these with NBR 6123 (1988). Two models and five codes of wind loads are analyzed: Jackson and Hunt (1975) and e Davenport, Surry e Lemelin (1988) Models and Brazilian Association of Technical Standards: Wind Load on Buildings, NBR 6123 (1988); European Standard: Eurocode1: Basis of Design and Actions on Structures, CEN TC 250: 2002; Australian/New Zealand Standard: Minimum Design Loads on Structures, AS/NZS 1170.2: 2002; Architectural Institute of Japan AIJ: 2004; American Society of Civil Engineering Standard, ASCE 7-95 (ASCE 7-95), Minimum Design Loads for Buildings and Other Structures; National Building Code of Canada, 2005, (NRCC 2005) codes. This study focuses not only the comparison of the response estimated by international codes nominees, but also a data bank of wind tunnel data to validate this tool based on empirical expressions. The comparison of the patterns shows a lack of consideration for international harmonization of the parameters to be employed for the calculations of wind loads. These differences in defining the basic parameters for the wind loading on structures determines difficulties to unify the formats recommended in the prediction of wind loads. Compared to the experimental data, the patterns will generally show up conservative for both types of mounts analyzed, symmetrical and asymmetrical, for both types of terrain, both considering 2D or 3D.
Martinez, Hugo. "Contribution à la modélisation du transport éolien de particules : mesures de profils de concentration en soufflerie diphasique." Université Joseph Fourier (Grenoble), 1996. http://www.theses.fr/1996GRE10032.
Full textSanz, Rodrigo Javier. "On antarctic wind engineering." Doctoral thesis, Universite Libre de Bruxelles, 2011. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209953.
Full textThe first issue in remote places like Antarctica is the lack of site wind measurements and meteorological information in general. In order to complement this shortage of information various meteorological databases have been surveyed. Global Reanalyses, produced by the European Met Office ECMWF, and RACMO/ANT mesoscale model simulations, produced by the Institute for Marine and Atmospheric Research of Utrecht University (IMAU), have been validated versus independent observations from a network of 115 automatic weather stations. The resolution of these models, of some tens of kilometers, is sufficient to characterize the wind climate in areas of smooth topography like the interior plateaus or the coastal ice shelves. In contrast, in escarpment and coastal areas, where the terrain gets rugged and katabatic winds are further intensified in confluence zones, the models lack resolution and underestimate the wind velocity.
The Antarctic atmospheric boundary layer (ABL) is characterized by the presence of strong katabatic winds that are generated by the presence of surface temperature inversions in sloping terrain. This inversion is persistent in Antarctica due to an almost continuous cooling by longwave radiation, especially during the winter night. As a result, the ABL is stably stratified most of the time and, only when the wind speed is high it becomes near neutrally stratified. This thesis also aims at making a critical review of the hypothesis underlying wind engineering models when extreme boundary layer situations are faced. It will be shown that the classical approach of assuming a neutral log-law in the surface layer can hold for studies of wind loading under strong winds but can be of limited use when detailed assessments are pursued.
The Antarctic landscape, mostly composed of very long fetches of ice covered terrain, makes it an optimum natural laboratory for the development of homogeneous boundary layers, which are a basic need for the formulation of ABL theories. Flux-profile measurements, made at Halley Research Station in the Brunt Ice Shelf by the British Antarctic Survery (BAS), have been used to analyze boundary layer similarity in view of formulating a one-dimensional ABL model. A 1D model of the neutral and stable boundary layer with a transport model for blowing snow has been implemented and verified versus test cases of the literature. A validation of quasi-stationary homogeneous profiles at different levels of stability confirms that such 1D models can be used to classify wind profiles to be used as boundary conditions for detailed 3D computational wind engineering studies.
A summary of the wind engineering activities carried out during the design of the Antarctic Research Station is provided as contextual reference and point of departure of this thesis. An elevated building on top of sloping terrain and connected to an under-snow garage constitutes a challenging environment for building design. Building aerodynamics and snowdrift management were tested in the von Karman Institute L1B wind tunnel for different building geometries and ridge integrations. Not only for safety and cost reduction but also for the integration of renewable energies, important benefits in the design of a building can be achieved if wind engineering is considered since the conceptual phase of the integrated building design process.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished
Demarco, Giuliano. "Simulações em laboratório de escoamentos em meios estratificados." Universidade Federal de Santa Maria, 2013. http://repositorio.ufsm.br/handle/1/3916.
Full textIn the present thesis, two distinct scientific problem in fluid mechanics are studied using laboratory observation techniques. In the first of them, a tank was used to simulate microburst propagation. In the experimental set-up, the flow was driven by combined impinging jet and density perturbations forcing with the aim of determining their relative influence on the overall microburst behaviour and, in particular, the initiation and structural evolution of the resulting vortex. These results were compared with those reported in previous simulation works. Such comparisons showed that the laboratory model may satisfactorily reproduce relevant aspects of a microburst. An expression for the characteristic microburst propagation velocity was derived, accounting for the combined effects of forced velocity and flotation forces generated by the density difference. The vortex structure is largely affected by the forcing type. The succession of vortex is best defined when a large density perturbation is combined with a weak jet impingement. The opposite configuration causes a main vortex to be succeeded by a wake where vortex structures are not clearly defined. In the second part, experiments were conducted in a wind tunnel above a cooled surface with the aim of determining the influence of the thermal stratification on turbulence-related quantities. The experimental apparatus consists of an aluminum plate inserted at the bottom surface of the test section, which is then cooled until 5ºC, so that a stably stratified surface is formed. As wind speeds increase, such a stable layer is soon destroyed. Data show that quantities such as temperature, variances, dissipation rates and turbulent fluxes are substantially reduced when a stratification is present. On the other hand, third and fourth order statistical moments, as well as the mean wind speed are very slightly affected by the stratification.
Neste trabalho, dois problemas científicos distintos de mecânica dos fluídos são estudados utilizando-se técnicas de observação em laboratório. no primeiro deles, utilizou-se observações em tanque para simular microbursts. O escoamento foi induzido através da combinação de dois processos definidos como jato incidente e perturbações de densidade, com o objetivo de determinar a sua influência sobre o comportamento de forma geral do microbursts e, em particular, o começo e a evolução estrutural dos vórtices resultantes. Estes resultados foram comparados com trabalhos anteriores. Uma expressão para a velocidade característica de propagação do microburst foi obtida, representando os efeitos combinados de velocidade forçada e as forças de perturbação gerados pela diferença de densidade, cujas previsões estão em boa concordância com os dados experimentais. A estrutura do vórtice é em grande parte afetada pelo tipo de forçante. A sucessão de vórtices é melhor definida quando a influência da perturbação de densidade se destaca sobre a de jato incidente. A configuração oposta provoca um vórtice principal a ser sucedido por uma esteira, no qual as estruturas dos vórtices não são claramente definidas. Em uma segunda etapa, experimentos foram realizados em túnel de vento sobre uma superfície resfriada para verificar- se a influência da estratificação térmica sobre quantidades associadas a um escoamento turbulento. No aparato experimental, uma placa de alumínio foi inserida na superfície inferior da seção de testes e resfriada até atingir uma temperatura de 5ºC, com o objetivo de verificar a formação de uma camada limite térmica estável e a influência da mesma sobre as grandezas analisadas. É possível observar a formação de uma camada estratificada, e logo destruída conforme os valores de vento aumentam. Os dados analisados, mostram uma redução substancial nos casos de vento mais fraco para as grandezas como temperatura, variâncias, taxas de dissipação e fluxos turbulentos. Por outro lado, momentos estatísticos de terceira e quarta ordem, assim como a velocidade média do vento foram pouco afetados pela estratificação.
北村, 圭一, Keiichi KITAMURA, 啓伺 小澤, Hiroshi OZAWA, 勝祥 花井, Katsuhisa HANAI, 浩一 森, Koichi MORI, 佳朗 中村, and Yoshiaki NAKAMURA. "極超音速TSTOにおける衝撃波干渉・境界層剥離を伴う流れ場の解析." 日本航空宇宙学会, 2008. http://hdl.handle.net/2237/13872.
Full textVecina, Tanit-Daniel Jodar. "Investigação da camada limite atmosférica simulada em túnel de vento no topo de morros utilizando dinâmica dos fluídos computacional (CFD)." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2017. http://hdl.handle.net/10183/158347.
Full textThe shape of the wind velocity profile changes according to local features of terrain shape and roughness, which are parameters responsible for defining the Atmospheric Boundary Layer (ABL) profile. Air flow characteristics over and around landforms, such as hills, are of considerable importance for applications related to Wind Farm and Turbine Engineering. The air flow is accelerated on top of hills, which can represent a decisive factor for Wind Turbine placement choices. The present work focuses on the study of ABL behavior as a function of slope and surface roughness of hill-shaped landforms, using the Computational Fluid Dynamics (CFD) to build wind velocity and turbulent intensity profiles. Reynolds-Averaged Navier-Stokes (RANS) equations are closed using the SST k-ω turbulence model; numerical results are compared to experimental data measured in wind tunnel over scale models of the hills under consideration. Eight hill models with slopes varying from 25° to 64° were tested for two types of terrain categories in 2D and 3D, and two analytical codes are used to represent the inlet velocity profiles. Numerical results for the velocity profiles show differences under 4% when compared to their respective experimental data. Turbulent intensity profiles show maximum differences around 7% when compared to experimental data, this can be explained by not being possible to insert inlet turbulent intensity profiles in the simulations. Alternatively, constant values based on the averages of the turbulent intensity at the wind tunnel inlet were used. The 3D models present greater concordance in the speed results than the 2D models and that in addition the greater the slope of the hill, the greater the agreement with the experimental measurements.
Murray, Henry Hall IV. "Turbulence and Sound Generated by a Rotor Operating Near a Wall." Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/71332.
Full textMaster of Science
Poette, Christopher. "La fragmentation du paysage : impact sur l'écoulement atmosphérique et la stabilité au vent des peuplements forestiers." Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0387/document.
Full textAt present only the characteristics of a forest stand and its immediate environment are taken into account in calculating forest wind risk. However, it is known that the wind is strongly affected by the surfaces over which it has previously flowed. Forest edges in particular play an important role in determining the characteristics of the atmospheric flow by generating increased turbulence, triggering the formation of coherent tree scale structures. In a fragmented landscape, consisting of surfaces of different heights and roughness, the multiplicity of edges may have cumulative effects at the regional scale leading to increased forest damage during storms. Flow changes in the atmospheric boundary-layer across surface roughness changes have received extensive study in the past because of their importance in determining velocities, turbulence levels and exchange between the atmosphere and biosphere or ground. There have also been a number of studies across single forest edges both in the field, wind-tunnels and computer models. However, there have been no studies of flow across multiple forest edges or the impact of forest fragmentation on the characteristics of the boundary-layer. The only studies on multiple surface changes have been wind-tunnel examination of the flow though and across multiple wind-breaks. In this thesis we show results from a series of wind tunnel experiments on a range of levels of forest fragmentation. Five gap spacings (L = ~ 5, ~ 10, ~15, ~20, ~30h, where L is the length of the gap and h is the canopy height) were investigated using 3D laser doppler velocimetry in order to assess the effects of fragmented landscapes on mean and turbulent wind characteristics. The fragmentation was two-dimensional with the transition between forest and gaps only being along the wind direction and the forest and gaps were continuous perpendicular to the wind direction. The wind speeds and turbulence characteristics are compared against measurements from a single forest edge in the wind tunnel, which acts as a reference. No enhancement of turbulence formation at a particular level of fragmentation was observed but there was a consistent pattern of wind speed and turbulence back from the first edge of each simulation with the horizontal velocity at tree top increasing and the turbulent kinetic energy decreasing as gap size increased. We also compare mean wind speeds (U and W) and turbulence characteristics (variance in u, v, and w; skewness in U, V, and W; Reynold’s stress, and TKE) at all points in the experimental measurement domain of the wind tunnel with Large Eddy Simulation (LES) results, which allows us to confirm the validity of the LES calculations and to conduct a wider range of experiments than was possible in the wind-tunnel. The results demonstrate the importance of the frontal area index or roughness density of elements (in this case trees) in determining the nature of the flow and the effective roughness of the overall surface. They also show that as the gaps between forest blocks increases the flow transitions (at a gap size between 10 to 15 tree heights) from flow comparable to that over a continuous forest to flow across a set of isolated forest blocks
Sheng, Risheng. "Application de l’approche de simulation des grandes échelles à l’évaluation des charges de vent sur les structures." Thesis, Ecole centrale de Nantes, 2017. http://www.theses.fr/2017ECDN0030/document.
Full textHigh-rise buildings are built with increasingly low weight and structural damping in relation to the evolution of construction techniques and materials. The understanding of dynamic wind loads is an important issue for the design of high-rise buildings in order to guarantee their structural safety. The objective of the present work is to assess the ability of large eddy simulation (LES) to predict wind loads on structures and to investigate the influence of the inflow boundary conditions of a LES simulation on these loads. Experiments were carried out at a small scale in the NSA atmospheric wind tunnel of CSTB to document the modeled atmospheric boundary layer, to characterize its interaction with a building and the resulting static and dynamic wind loads. The wake flow around the building has been characterized by PIV measurements. Global and local wind loads were measured by a high frequency force balance and high frequency pressure taps. These wind tunnel experiments allowed for the development of an inflow turbulence generator for the LES simulation,which was aimed at reproducing the main characteristics of turbulence in the boundary layer. The database also made it possible to assess the quality of the results of the LES simulations carried out with the OpenFOAM code in the same configuration as the experiment. The use of both the new turbulence generator and a degraded one that does not account for all the characteristics of the flow has made it possible to show the necessity to reproduce the characteristics of the upstream wind flow in order to access the dynamic wind loads on the building
Blackman, Karin. "Interactions multi-échelles entre la basse atmosphère et la canopée urbaine." Thesis, Ecole centrale de Nantes, 2017. http://www.theses.fr/2017ECDN0028.
Full textThe urban boundary layer consists of complex coherent structures, such as large-scale low momentum regions and intermittent turbulent sweeps and ejections, which are responsible for the transport of heat, momentum and pollution. Although these structures have been well identified, their quantitative relationship with the flow inside the canopy is still unknown. Wind tunnel modelling of flow over simplified rough terrain consisting of either three-dimensional or twodimensional roughness elements are able to reproduce these structures and are used to investigate the nonlinear relationship between large-scale momentum regions and small-scales induced by the presence of the roughness. As the temporally resolved small-scale signalis not available Linear Stochastic Estimation is used to decompose the flow into large and small-scales and confirm that the large-scale structures within the overlying boundary layer influence the small-scales close to the roughness through a non-linear mechanism similar to amplitude modulation. Changing terrain configuration from 3D to 2D roughness results in a modification of the non-linear relationship closer to the shear layer that develops near the top of the obstacles. The full turbulent kinetic energy (TKE) budget including dissipation is calculated using an LE-PIV model and demonstrates that small-scale structures within the shear layer are important to the production, transport and dissipation of energy. Finally, triple decomposition of theTKE budget confirms that the non-linear relationship that exists between large-scale momentum regions and small-scales close to the roughness is related to energy transfer between these structures
ORLANDO, MAURIZIO. "Indagine Sperimentale ed Analisi Numerica degli Effetti di Interferenza Indotti dal Vento su Due Torri di Raffreddamento Adiacenti." Doctoral thesis, 1999. http://hdl.handle.net/2158/676032.
Full textBor-Yann, Pan, and 潘伯彥. "Generation of Boundary Layer Flows in A Wind Tunnel." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/39772998861264731143.
Full text國立中興大學
土木工程學系
87
Human behavior are always within hundreds meters near the earth surface. Atmosphere within this region is called the atmospheric boundary layer flow. Because of the increasing pollution sources and number of high-rise buildings, and higher demands of human living quality, it becomes more important to carry out researches on atmospheric characteristics. The study concentrates on generation of atmospheric boundary flows in an open wind tunnel. The outcomes would be used as the basis of future experiments involving atmospheric boundary layer flows. In the study, triangular vortex generators and proper roughness elements, suggested by Irwin(1981), are adopted to simulate three different types of boundary layer flows, corresponding respectively to those in the rural, suburban and urban terrains . After the resulting mean and fluctuating velocity profiles are measured, the effects from the selection of the arrangements are assessed.
Lo, Kuoshien, and 羅國憲. "A Study on Wind Tunnel Boundary Layer Generation with." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/67681704040814364596.
Full text國立高雄應用科技大學
土木工程與防災科技研究所
91
ABSTRACT Almost all buildings and civil engineering structures stand in the earth ground boundary layer. To stimulate this condition, we must generate boundary layer in the wind tunnel’s test section. Two types of boundary layer generators could be used : elliptical or triangular. For the sake of easy working, we took the triangular type. According to Irwin’s study, the desired wind velocity profile should be located downstream the triangular boundary layer generator at a distance 6 times the height of boundary layer generator. In this study we tried to shorten the distance with punched triangular boundary layer generator. We stimulated two types of wind velocity profile, α=0.12 and α=0.36. In each condition we tried two value of boundary layer height, 30cm and 40cm. Also, we changed the fan speed of the wind tunnel. The area of the punched generators should be larger than that of non-punched generators to compensate the area of holes. The results show that the punched generators will generate better wind velocity profile in most cases. But the gradient wind velocity decreases in most cases too. This unexpected phenomenon should be studied at the next step.
Farrell, Thomas Elmer Miller L. Scott. "Development of a new boundary layer control technique for automotive wind tunnel testing." Diss., 2005. http://il.proquest.com/products_umi/dissertations.
Full text"December 2005." Title from PDF title page (viewed on April 22, 2007). Thesis adviser: L. Scott Miller. UMI Number: AAT 1436555 Includes bibliographic references (leaves 50-51).
Farrell, Thomas Elmer. "Development of a new boundary layer control technique for automotive wind tunnel testing." Thesis, 2005. http://hdl.handle.net/10057/760.
Full textThesis (M.S.)--Wichita State University, College of Engineering, Dept. of Aerospace Engineering.
"December 2005."
Tzeng, Yu-ting, and 曾鈺婷. "Field measurements and wind tunnel investigation on the characteristics of atmospheric boundary layer." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/10388765580135443437.
Full text淡江大學
土木工程學系碩士班
99
The population is growing rapidly in Taiwan, and as a result the geographical area encapsulating the population is decreasing dramatically. This is forcing people to use space more efficiently, and this was reflected by constructing tall, multi-storey buildings. Therefore, it is often common to see a lot of tall buildings in modern and congested cities. However, according to reinforcing of wind, tall buildings are of exceptional height and relatively low mass. These two characteristics have their advantages and disadvantages. Since Taiwan is located in the subtropical zone, it has northeast monsoon in the winter and typhoons in the summer, so people have to be extremely considerate when it comes to designing tall buildings in such conditions. It is critically important that they understand the causes and effects of wind power on the buildings’ physical structures. For example, tall constructions are stiffer than low ones; however they suffer more pressure from wind. The main objective of this research is to discuss the different characteristics of atmospheric boundary layer between Taipei city and Danshui. It also focuses on the comparison between the wind tunnel experiments and field measurement. It includes characteristics of atmospheric boundary layer, wind profile, turbulence intensity, turbulence length scale, turbulence spectrum, gust factor, and coherence function. According to the experiment result, it shows that the average intensity of wind velocity have some effects on the wind profile figure under a strong wind circumstance; the turbulence intensity decrease steadily when there is an increase on the average intensity of wind velocity. On the other hand, the turbulence length scale expands while the average intensity of wind velocity increases. The Von-Karman spectrum density function represent the recommended figure of local’s normal wind characteristics. Different level of height of Coherence Function satisfied Davenport’s recommended figure. Under the accurate reduced scale conditions, both the Practical situation model and wind tunnel investigation have similar outcome after comparing the result of the Characteristics of wind field and Field measurement.
Kuo, Ting-Wei, and 郭庭瑋. "Wind tunnel investigation on the different topography of characteristics of atmospheric boundary layer." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/38362739898722682801.
Full text淡江大學
土木工程學系碩士班
99
Before, we only have three typical terrain’s roughness blocks. If we want to know a real topography’s wind feature, we have to make a reduced scale’s model to simulate it. But it will be waste human resources and spend a lot of time and money. So if we can find some way to use roughness blocks to simulate the real topography, it will be more efficiently. On the other hand, in the field measurement we can’t got the information of the turbulence. If we successfully use the way to simulate terrain, we can got more information of terrain. The results show that we can use the mean height of the build and density of the terrain to simulate the real topography. In roughness block’s experiment, we successfully simulate the wind profile, turbulence intensity and turbulence length scale.
Chiang, Yun-yu, and 蔣昀祐. "A Study on Simulating the Atmospheric Boundary Layer Formation in Small Low Speed Wind Tunnel - Take Wind Tunnel in CYUT as an example." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/01371503964218027149.
Full text朝陽科技大學
建築及都市設計研究所
99
Wind tunnel laboratory in Architecture Department of CYUT is arranged for simulating the wind field in urban environment and building surroundings for research and experiments. It is planned to offer reference for site and buildings location arrangement when under design and planning. To do the urban design, architectural design, green design, structure, disaster prevention, building physical condition and equipment design, wind tunnel experiment practice is important for students to understand the wind field changing in the environment by using model simulation. It is helpful to realize the actual situation in the environment to do the urban planning and building design. Main in research is to establish the simulating atmospheric boundary layer in wind tunnel according to the different site conditions. The wind field will be affected by various site localities like seashore, plain, suburb, and urban type of terrain to form different shape of atmospheric boundary layer. Passive devices such as spires, barriers, and roughness elements were implemented in the tunnel for the simulations. We try to use different size of passive devices and spacing to generate our exclusive atmospheric boundary layer in our low speed, small size wind tunnel. These results will be judged to correct the drift or partly drift from the theory profile line of the atmospheric boundary layer by changing the size and spacing of passive devices. Finally, we will have a suitable atmospheric boundary layer which fit the theory profile line as the achievement. These wind profile will be suitable for the experiment and relevant researches. The purposes of this research are trying to can build up our wind tunnel experiment simulation abilities effectiveness and efficiency in order to help students to understand the wind effects in the environment and promote cooperation of academic circle and the field. Also these will help us to construct the data base for offering references to other researches.
Chien-EnHuang and 黃健恩. "Analysis and Measurements of Wakes from Multi-blade Turbines in a Boundary-Layer Wind Tunnel." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/s2g82w.
Full text國立成功大學
工程科學系
106
An experiment was carried out to study complex turbulence in the wakes originated from stand-alone 2, 3 and 4-blade wind turbines placed in the turbulent boundary-layer wind tunnel (turbulence intensity of 10% at the hub height) with two conditions:(1) the measurements in the vertical plane, and (2) the measurements in the horizontal plane when the turbine works in +20°,-20° and 0° yaw angle conditions. The calibration-free Cobra Probe was used to measure the three instantaneous velocity components in the wakes from the stand-alone turbine. Turbulence key statistics are analyzed and presented, including time-averaged velocity, turbulence intensity, momentum flux, and power spectrum. Besides, we use the BEM theory to predict the streamwise wind velocity to compare with the results of the measurements at the downwind position X/D=1 in the turbulence (the data obtained from this experiment) and uniform incoming flow (the data duplicate from the reference, Lyu (2017)[1]). The results of the measurements indicate that the distribution of time-averaged velocity declines immediately downstream of the turbine models and then recovers with the wake-wise direction. The turbulence intensity has a strong enhancement at the tip-levels in the near-wake region. Momentum flux demonstrates how the kinetic energy of the flow is transported to recover the velocity deficit in the wakes. In particular, the wakes of the statistics are deflected to the side when the turbine works in a yaw angle condition, and the maximum of the key turbulence statistics are in the four-blade turbine case. The plots of the energy spectrum from the results are close to the inertial subrange with a global slope of -5/3 to confirm further the measured device is reliable. The comparisons of the prediction from the BEM theory and the measurements in the turbulence and uniform inflow conditions demonstrate that the wind velocity deficit recovers faster in the turbulence case because of the turbulence mixing, and the BEM theory can be used to predict the approximate value of the wind velocity in the near wake.
Kuester, Matthew. "Acoustics in the Klebanoff-Saric Wind Tunnel: Background Identification, Forcing, and Active Control." Thesis, 2012. http://hdl.handle.net/1969.1/ETD-TAMU-2012-05-10731.
Full textHofferth, Jerrod William. "Boundary-Layer Stability and Transition on a Flared Cone in a Mach 6 Quiet Wind Tunnel." Thesis, 2013. http://hdl.handle.net/1969.1/150990.
Full textSt, Hill Simon. "Drag reduction of cube-van through boundary-layer control: wind tunnel experiments and prototype road tests." Thesis, 1993. http://hdl.handle.net/2429/2358.
Full textHo, Kuo Ching, and 郭敬和. "The Wind Tunnel to Study The Correlations of Surface Wind Pressure of High Rise Building in Turbulent Boundary Layer Flow." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/06745190856225647867.
Full text國立海洋大學
河海工程學系
90
The experiments are conducted on the wind tunnel to study the correlations of surface wind pressure of high rise building in the urban terrain type of neutral turbulent boundary layer flow. The geometric scale of 1/500 of square prismatic model is used in the wind tunnel experiment. Results show that the simulated neutral turbulent boundary layer flow is good in comparison with Counihan’s field data and Von Karman spectrum equation. In the present study, the probability density function (PDF) of fluctuating wind pressure is presented. The wind pressure spectrum and cross spectrum for different measured surface taps are also presented. Wind attack angles on the building surface pressure variations are measured and analyzed.
Manu, K. V. "Experiments on the Late Stages of Boundary Layer Transition." Thesis, 2013. http://hdl.handle.net/2005/3285.
Full textFreels, Justin Reed. "An Examination of Configurations for Using Infrared to Measure Boundary Layer Transition." Thesis, 2012. http://hdl.handle.net/1969.1/ETD-TAMU-2012-08-11476.
Full textHuang, Cheng-Wen, and 黃政文. "Wind tunnel study on the flow and dispersion characteristics for a turbulent boundary layer flow over two consecutive embankments with different spaces." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/01057697019547843189.
Full text國立臺灣海洋大學
河海工程學系
98
The wind tunnel experiments were conducted to study the flow and dispersion characteristics for a turbulent boundary layer flow over two consecutive embankments with different spaces. The upwind slope angle and down slope angle of the embankment was the same. Two slope angles of 27o and 45o were adopted. Two consecutive embankments were arranged with spaces of 0L, L, 2L, and 3L. Here L is the top surface length of the embankment. The flow and dispersion characteristics included the mean velocity, turbulence intensity, Reynolds stress, and dispersion parameters. Effects of the embankment slope angles and spaces between the two embankments on the flow and dispersion were investigated in the study.
(10721112), Joshua Craig Ownbey. "Preliminary Design of a High-Enthalpy Hypersonic Wind Tunnel Facility and Analysis of Flow Interactions in a High-Speed Missile Configuration." Thesis, 2021.
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