Dissertations / Theses: 'Wind shear'

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Belderrain, José Luiz Rocha. "Desempenho ótimo de aviões voando em "wind-shear"." Instituto Tecnológico de Aeronáutica, 1991. http://www.bd.bibl.ita.br/tde_busca/arquivo.php?codArquivo=1785.

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Esta dissertação considera a aplicação da teoria de controle ótimo a um avião que está voando através de "wind-shear"; para reduzir o efeito da força desaceleradora aplicada pela massa de ar que pode ser da mesma ordem de magnitude que o arrasto total da aeronave o índice de desempenho escolhido é a minimização dos desvios da trajetória atual em relação a uma trajetória nominal. O cenário do problema e o modelamento matemático são bastante realistas, tendo sido utilizado para a aeronave um modelo de corpo rígido. Foi com sucesso tanto pelo método "exato" (estrutura de contato) como por um método aproximedo uma limitação de ângulo de ataque. Para resolver o problema matemático resultante (sistema de equações diferenciais ordinárias com múltiplas condições de contorno) foram utilizados, conjuntamente, o método dos múltiplos tiros e um método de homotopia modificado. Desta forma, foram obtidas várias trajetórias ótimas, onde se nota que a estratégia básica de controle é a manutenção da velocidade em relação ao solo. Algumas leis de controle simplificadas foram analisadas; as leis de atitude longitudinal constante, de realimentação do ângulo da trajetória e de realimentação da aceleração na direção da trajetória apresentaram um desempenho semelhante, ligeiramente inferior ao ótimo. Possivelmente, uma lei de controle mais elaborada conseguiria reproduzir, com boa aproximação, as trajetórias ótimas.

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Guldsten, Jon Didriksen. "Influence on wind shear and turbulence in flow over obstacles." Thesis, Norwegian University of Science and Technology, Department of Energy and Process Engineering, 2010. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-10029.

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A wind tunnel study of speed-up effects above the very crest of a sharp-edged escarpment and a hill peak in a simulated atmospheric boundary layer has been carried out. It was desired to do a part-deep simulation of an atmospheric boundary that could be found above sea or coastal area exposed to the open sea. Because of the limited work section length was it used a modified roughness, barrier and mixing-device developed by Counihan to accelerate the boundary layer growth. The mean velocity, integral length scales, power spectrum and turbulence intensity in the simulated boundary layer were compared with full scale empirical data. It showed good agreement except for the turbulence intensity which was too low. Speed-up effects for the mean horizontal velocity and the longitudinal turbulence intensity above the very crest of an escarpment and a hill peak were investigated in the simulated atmospheric boundary layer. From the results it was observed that the speed-up effect gave a decrease in the turbulence intensity and a more uniform profile with height. A considerably increase of the horizontal mean velocity in the lowest part of the flow was also observed. Scaled-up data from the wind tunnel experiment were compared with estimations from the Norwegian standard and potential flow with varying degree of agreement.

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Zarraonandia, Gaizka. "Influence on wind shear and turbulence in flow over obstacles." Thesis, Norwegian University of Science and Technology, Department of Energy and Process Engineering, 2010. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-10165.

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A wind tunnel study of speed-up effects above the very crest of a sharp-edged escarpment and a hill peak in a simulated atmospheric boundary layer has been carried out. It was desired to do a part-depth simulation of an atmospheric boundary that could be found above sea or coastal area exposed to the open sea. Because of the limited work section length it was used a modified roughness, barrier and mixing-device method developed by Counihan to accelerate the boundary layer growth. The mean velocity, integral length scales, power spectrum and turbulence intensity in the simulated boundary layer were compared with full scale empirical data. It showed good agreement except for the turbulence intensity which was too low. Speed-up effects for the mean horizontal velocity and the longitudinal turbulence intensity above the very crest of an escarpment and a hill peak were investigated in the simulated atmospheric boundary layer. From the results it was observed that the speed-up effect gave a decrease in the turbulence intensity and a more uniform profile with height. In addition, it was observed a considerably increase of the horizontal mean velocity in the lowest part of the atmospheric boundary layer. Scaled-up data from the wind tunnel experiment were compared with estimations from the Norwegian standard and potential flow with varying degree of agreement.

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Caeiro, Olaio Valente Maria Antonia. "Effects of directional wind shear on orographic gravity wave drag." Thesis, University of Reading, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325212.

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Indriyanto, Toto. "Nonlinear flight control system for lateral manoeuvres in wind shear." Thesis, Cranfield University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.273525.

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Guarino, Maria Vittoria. "Mountain wave breaking in atmospheric flows with directional wind shear." Thesis, University of Reading, 2017. http://centaur.reading.ac.uk/75850/.

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In this thesis, mountain wave breaking triggered by directional wind shear is investigated using numerical simulations of idealized and semi-idealized orographic flows. Idealized simulations are used to produce a regime diagram to diagnose conditions for wave breaking in Richardson number-dimensionless mountain height parameter space. It is found that, in the presence of directional shear, wave breaking can occur over lower mountains than in a constant-wind case. Furthermore, the extent of regions within the simulation domain where Clear-Air Turbulence (CAT) is expected increases with terrain elevation and background wind shear intensity. Analysis of the model output, supported by theoretical arguments, suggest the existence of a link between wave breaking and the relative orientations of the incoming wind vector and the horizontal velocity perturbation vector. This condition provides a possible diagnostic for CAT forecast in directional shear flows. The stability of the flow to wave breaking in the transition from hydrostatic to nonhydrostatic mountain waves is also investigated. Wave breaking seems to be inhibited by non-hydrostatic effects for weak wind shear, but enhanced for stronger wind shear. In the second part of the thesis, a turbulence encounter observed over the Rocky Mountains (in Colorado, USA) is studied. The role of directional shear in causing wave breaking is isolated from other possible wave breaking mechanisms through various sensitivity tests. The existence of an asymptotic wake, as predicted by Shutts for directional shear flows, is hypothesized to be responsible for a significant downwind transport of unstable air detected in cross-sections of the flow. Finally, critical levels induced by directional shear are studied by spectral analysis of the horizontal velocity wave perturbations. This is done for a fully idealized flow and for the more realistic flow corresponding to the investigated turbulence encounter. In these 2D power spectra, a rotation of the most energetic wave modes with the background wind and their selective absorption can be found. Such behaviour is consistent with the mechanism leading to wave breaking in directional shear flows.

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Baseer, Mohammed Abdul. "Wind resource assessment and GIS-based site selection methodology for efficient wind power deployment." Thesis, University of Pretoria, 2017. http://hdl.handle.net/2263/61314.

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An enormous and urgent energy demand is predicted due to the growing global population, increase in power intensive industries, higher living standards, electrification of remote areas, and globalisation (transportation). Moreover, the global consciousness about the harmful effects of traditional methods of power generation on the environment. That, in turn, has created a need to strategically plan and develop renewable and sustainable energy generation systems. This study presents a wind resource assessment of seven locations proximate to the largest industrial hub in the Middle East, Jubail Industrial City, Kingdom of Saudi Arabia, and a Geographic Information System, GIS based model considering a multi-criteria wind farm site suitability approach for the entire Kingdom of Saudi Arabia and elsewhere. The hourly mean wind speed data at 10, 50 and 90 m above the ground level (AGL) over a period of five years was used for a meteorological station at the Industrial Area (Central) of Jubail. At the remaining six sites, the meteorological data were recorded at 10 m AGL only. Five years of wind data were used for five sites and three years of data were available for the remaining one site. At the Industrial Area (East), the mean wind speeds were found to be 3.34, 4.79 and 5.35 m/s at 10, 50 and 90 m AGL, respectively. At 50 and 90 m AGL, the availability of wind speed above 3.5 m/s was more than 75%. The local wind shear exponent, calculated using measured wind speed values at three heights, was found to be 0.217. The mean wind power density values at measurement heights were 50.92, 116.03 and 168.46 W/m2, respectively. After the assessment and comparison of wind characteristics of all seven sites, the highest annual mean wind speed of 4.52 m/s was observed at Industrial Area (East) and the lowest of 2.52 m/s at the Pearl Beach with standard deviations of 2.52 and 1.1 m/s, respectively. In general, at all sites, the highest monthly mean wind speed was observed in February/June and the lowest in September/October. The period of higher wind availability coincides with a high power demand period in the region attributable to the air conditioning load. The wind rose plots show that the prevailing wind direction for all sites was from the north-west. Weibull parameters for all sites were estimated using maximum likelihood, least-squares regression method (LSRM), and WAsP algorithm. In general, at all sites, the Weibull parameter, c, was the highest in the months of February/June and the lowest in the month of October. The most probable and maximum energy carrying wind speed was determined by all three methods. The highest value of most probable wind speed was found to be in the range of 3.2 m/s to 3.6 m/s at Industrial Area (East) and the highest value of maximum energy carrying wind speed was found to be in the range 8.6 m/s to 9.0 m/s at Industrial Area 2 (South) by three estimation methods. The correlation coefficient (R2), root mean square error (RMSE), mean bias error (MBE), and mean bias absolute error (MAE) showed that all three methods represent wind data at all sites accurately. However, the maximum likelihood method is slightly better than LSRM, followed by WAsP algorithm. The wind power output at all seven sites, from five commercially available wind turbines of rated power ranging from 1.8 to 3.3 MW, showed that Industrial Area (East) is most promising for wind farm development. At all sites, based on percentage plant capacity factor, PCF, the 1.8 MW wind turbine was found to be the most efficient. At Industrial Area (East), this wind turbine was found to have a maximum PCF of 41.8%, producing 6,589 MWh/year energy output. The second best wind turbine was 3 MW at all locations except the Al-Bahar Desalination Plant and Pearl Beach. At both of these locations, 3.3 MW was the next best option. The energy output from the 3 MW wind turbine at Industrial Area (East) was found to be 11,136 MWh/year with a PCF of 41.3%. The maximum duration of rated power output from all selected wind turbines was observed to be between 8 to 16.6% at Industrial Area 2 (South). The minimum duration of rated power output, less than 0.3% for all wind turbines, was observed at Pearl Beach. The maximum duration of zero power output of between 35 to 60% was also observed at Pearl Beach.
Thesis (PhD)--University of Pretoria, 2017.
Mechanical and Aeronautical Engineering
PhD
Unrestricted

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Stival, Leandro Jose Lemes. "A study on wind assessment on the wind power performance : wind shear and turbulence intensity effects besides the wake modeling for a single wind turbine." reponame:Repositório Institucional da UFPR, 2017. http://hdl.handle.net/1884/49088.

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Orientador : Prof. Dr. Alexandre Kolodynskie Guetter
Coorientador : Prof. Dr. Fernando Oliveira Andrade
Dissertação (mestrado) - Universidade Federal do Paraná, Setor de Tecnologia, Programa de Pós-Graduação em Engenharia de Recursos Hídricos e Ambiental. Defesa: Curitiba, 04/04/2017
Inclui referências : f.91-97
Resumo: A energia eólica cresceu significativamente, porém a eficiência de geração da fonte eólica gira em torno de 30% da energia cinética disponível no vento. Por este motivo é de extrema importância que estudos sejam elaborados afim de aumentar a eficiência na geração de energia. Este estudo visa investigar odesempenho da geração de energia eólica em dois parques eólicos situadosna América do Norte, através da investigação dos dados de vento e modelagem da esteira turbulenta. Os dados analisados são provenientes da turbina, SCADA, e dados coletados pelo LiDAR. A partir das análises dos dados de vento foram estimados parâmetros como tensão de cisalhamento do vento, rosa dos ventos, perfil de velocidade do vento e intensidade de turbulência. Portanto, aumentando a intensidade de turbulência, a energia gerada é superestimada em moderadas velocidades do vento e subestimada em altas velocidades do vento. Enquanto isso, os coeficientes de cisalhamento do vento variaram entre 0 e 0.2 para altas velocidades. Além disso, coeficientes de cisalhamento com valores elevados, perto de 0.4, foram encontrados em baixas velocidades do vento. Este trabalho visou também comparar modelos de esteira turbulenta de PARK (Jensen), Frandsen, Larsen and Eddy Viscosity (Ainslie) com resultados obtidos pelo LiDAR, além disso foi realizado uma simulação numérica da esteira turbulenta utilizando Fluent CFD com as equações médias de Reynolds (RANS) que resolvem o modelos de duas equações diferenciais para obter a viscosidade turbulenta. A turbulência foi fechada pelo modelo ?????, sendo o modelo de esteira turbulenta desenvolvido para uma única turbina num terreno plano. O modelo de PARK obteve os melhores resultados para linha de centro longitudinal em relação as velocidades de 6 a 8 ms-1. Entretanto, para velocidade de 9 a 12 ms-1 , o modelo de EDDY VISCOSITY apresentou o melhor desempenho. As análises de seção transversal apresentaram o modelo de PARK como melhor resultado para 500 m. Enquanto isso, para 700 m de seção transversal, o melhor desempenho foi obtido pelo modelo de LARSEN. Palavras-chave: Energia Eólica, Modelo de Esteira Turbulenta, LiDAR, Análises do Vento.
Abstract: Wind power has gained significant share in the global power production. However, the wind power output efficiency is only about 30% of the wind kinetic energy. Because of that, it is essential to study the efficiency of these power generation systems by assessing the effects that wind parameters and wakes will have on the whole system. Hence, a complete assessment of wind resources is crucial to retain full advantage of wind power. This study aims to investigate the efficiency of wind energy generation in two North American Wind Farms, through wind data investigation and wake modeling. The data analyzed are the SCADA data and the data collected by LiDAR measurements. The wind data analysis has estimated parameters as wind shear, wind rose, wind speed profile and turbulence intensity. Therefore increasing turbulence intensity the power output is overestimated at moderate wind speeds and underestimated at higher wind speeds. Meanwhile, the wind shear coefficients were found to vary between 0 and 0.2 at higher inflow velocities. High wind shear values, close to 0.4, were recorded for lower inflow velocities. The goal of the wake models is to simulate the turbine induced wind speed deficits and the ratio of restoration to the free stream velocity. This work has compared the PARK (Jensen), Frandsen, Larsen and Eddy Viscosity (Ainslie) models with LiDAR wake measurements, besides that it has performed a numerical simulation of the wind turbine wake using the Fluent CFD with the Reynolds Averaged Navier Stokes (RANS) equations that solves two differential equation model to obtain turbulent viscosity. The turbulence was closed by the ????? model, where the wake modeling has been developed for a single turbine on a flat terrain. In terms of centerline wake analysis, the PARK wake model yielded the best velocity simulations for inflow winds from 6 to 8 ms-1. However, the EDDY VISCOSITY wake model yielded the best performance for wind speed bins from 9 to 12 ms-1. The cross section wake analysis presented for the 500 m cross section, the domination by the PARK model. Meanwhile, along the 700 m cross section, the LARSEN wake model produced the best simulations. Key-words: Wind Power, Wake Modeling, LiDAR, Wind Analysis.

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Sycuro, Stephen J. "Radar turbulence estimates : effects of wind shear and reflectivity factor gradients." Thesis, Massachusetts Institute of Technology, 1985. http://hdl.handle.net/1721.1/58128.

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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric and Planetary Sciences, 1985.
Microfiche copy available in Archives and Science.
Bibliography: leaf 43.
by Stephen J. Sycuro.
M.S.

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Mu, K. L. "Investigation of tropospheric turbulence using the Adelaide VHF radar /." Title page, abstract and contents only, 1991. http://web4.library.adelaide.edu.au/theses/09SM/09smm941.pdf.

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Smith, Debra K. "Tropical cyclone development and intensification under moderate to strong vertical wind shear." Thesis, Monterey, California. Naval Postgraduate School, 1994. http://hdl.handle.net/10945/28618.

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Approved for public release; distribution is unlimited
A study was conducted to understand the physical mechanisms by which a tropical cyclone is able to develop and be maintained under moderate to strong vertical wind shear. The general approach was to describe case studies of three tropical cyclones in the western North Pacific that developed and/or intensified in the lee of another tropical cyclone. The data resources include high temporal and spatial resolution visible and infrared satellite imagery, operational subjective and objective analyses, plus special Tropical Cyclone Motion (TCM-90) high resolution (50 km) analyses and multi-quadric analyses. The three tropical cyclones developed and/or intensified under moderate to strong vertical wind shear that exceeded threshold values. The vertical wind shear was time dependent due to complex interactions with the leading tropical cyclone outflow, adjacent tropical upper tropospheric trough, and large-scale environment. Diurnal variability in strength of convection and outflow against the impinging flow led to fully exposed, partially exposed, or covered middle to lower tropospheric cyclonic circulation. Special characteristics of the monsoon trough circulation must create and sustain the tropical cyclone circulation against the tendency for the vertical wind shear to ventilate the vertical thermal and convective structure

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Woo, Tak Kwong. "Transitory control of separated shear layer using impulsive jet actuation." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/52980.

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The dynamics of controlled transitory 2- and 3-D attachment of the separated flow over a 2-D airfoil model are investigated in wind tunnel experiments. Pulsed actuation is effected on time scales that are an order of magnitude shorter than the characteristic convective time scale of the base flow by momentary jets that are generated by a spanwise array of combustion-based actuators. The effects of the transitory actuation on the aerodynamic characteristics of the airfoil are assessed using measurements of the global lift force and pitching moment and of streamwise distributions of surface pressure, and planar and stereoscopic particle image velocimetry (PIV) acquired phase-locked to the actuation waveform. A single spanwise-bounded actuation pulse leads to 2-D severing of the separated vorticity layer and the subsequent shedding of a large-scale stall vortex that are followed by momentary attachment of the upstream boundary layer and ultimately re-separation that are accompanied by a strong transitory change in the airfoil's circulation. It is shown that the primary mechanism for the attachment is alteration of the adverse pressure gradient of the separated base flow by local blockage of the momentary jet and.the formation of the large-scale stall vortex. The disparity between the characteristic time scales of flow attachment and subsequent separation [O(Tconv) and O(10Tconv), respectively] is exploited for temporal and spatial extensions of the attachment and enhancement of the global aerodynamic performance using strings of successive actuation pulses. Pulsed actuation effected by an unbounded actuator array leads to spanwise spreading of the induced transitory 3-D flow attachment well beyond the spanwise edges of the actuators. It is shown that 3-D pulsed actuation enhances the accumulation of vorticity over the airfoil and improves its aerodynamic performance compared to 2-D, spanwise-bounded actuation. When the airfoil is undergoing time-periodic pitch oscillations beyond its static stall margin, a sequence of staged 3-D actuation pulses coupled to the airfoil's motion can lead to reduced lift hysteresis and increased pitch stability (lower “negative damping”) that are typically associated with the presence of dynamic stall.

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Iannotti, Veronica. "Studio del fenomeno del "wind shear" e analisi dei principali sistemi di rilevamento." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/19047/.

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L'obiettivo di questa tesi di laurea è fornire un'analisi principalmente descrittiva del fenomeno del windshear, mettendo in evidenza quelle che risultano essere le condizioni meteorologiche sufficienti per la sua comparsa e gli effetti sulla stabilità dell'aeromobile provocati da una variazione del vettore vento. L'elaborato offre, inoltre, dei concetti base per il monitoraggio del windshear, attraverso lo studio di strumenti di "detection" e "warning" (quali RADAR, LIDAR e SODAR), sia da un punto di vista funzionale che matematico.

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Siveski, Zlatan. "Non-linear structural analysis of shear connected cavity walls subject to wind load." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq23496.pdf.

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Ninnemann, Todd A. "Aspirating probes for measurement of mean concentration and fluctuating quantities in supersonic air/helium shear layer." Thesis, This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-12232009-020346/.

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Jacobi, Christoph, and Manfred Ern. "Gravity waves and vertical shear of zonal wind in the summer mesosphere-lower thermosphere." Universität Leipzig, 2013. https://ul.qucosa.de/id/qucosa%3A16408.

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Gravity wave amplitudes and momentum fluxes derived from SABER temperature measurements are analysed together with Collm meteor radar zonal winds. The momentum flux (MF) divergence derived from the SABER temperatures shows a maximum that is found at greater altitudes during solar minimum than during solar maximum. Therefore, the zonal mean wind and wind shear profiles are shifted upwards then, leading to a modulation of the otherwise negative correlation between solar cycle and mesosphere/lower thermosphere winds.
Amplituden von Schwerewellen und zugehörigen Impulsflüsse werden zusammen mit Windmessungen des Meteorradars Collm analysiert. Die Impulsflussdivergenz, abgeleitet aus SABER-Temperaturprofilen, hat ein Maximum welches im solaren Minimum nach oben verschoben ist. Dadurch werden auch die Vertikalprofile des Zonalwindes und der Windscherung nach oben verschoben, wodurch die ansonsten negative Sonnenfleckenzyklusabhängigkeit des zonalen Windes in der Mesosphäre/unteren Thermosphäre im solaren Minimum umgekehrt wird.

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Vessby, Johan. "Shear walls for multi-storey timber buildings." Licentiate thesis, Växjö University, School of Technology and Design, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:vxu:diva-2420.

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Wind loads acting on wooden building structures need to be dealt with adequately in order to ensure that neither the serviceability limit state nor the ultimate limit state is exceeded. For the structural designer of tall buildings, avoiding the possibly serious consequences of heavy wind loading while taking account at the same time of the effects of gravitation can be a real challenge. Wind loads are usually no major problem for low buildings, such as one- to two-storey timber structures involving ordinary walls made by nailing or screwing sheets of various types to the frame, but when taller structures are designed and built, serious problems may arise.

Since wind speed and thus wind pressure increases with height above the ground and the shear forces transmitted by the walls increase accordingly, storey by storey, considerable efforts can be needed to handle the strong horizontal shear forces that are exerted on the bottom floor in particular. The strong uplift forces that can develop on the wind side of a structure are yet another matter that can be critical. Accordingly, a structure needs to be anchored to the substrate or to the ground by connections that are properly designed. Since the calculated uplift forces depend very much upon the models employed, the choice of models and simplifications in the analysis that are undertaken also need to be considered carefully.

The present licentiate thesis addresses questions of how wind loads acting on multi-storey timber buildings can be best dealt with and calculated for in the structural design of such buildings. The conventional use of sheathing either nailed or screwed to a timber framework is considered, together with other methods of stabilizing timber structures. Alternative ways of using solid timber elements for stabilization are also of special interest.

The finite element method was employed in simulating the structural behaviour of stabilizing units. A study was carried out of walls in which sheathing was nailed onto a timber frame. Different structural levels were involved, extending from modelling the performance of a single fastener and of the connection of the sheathing to frame, to the use of models of this sort for studying the overall structural behaviour of wall elements that possess a stabilizing function. The results of models used for simulating different load cases for walls agreed reasonably well with experimental test results. The structural properties of the fasteners binding the sheathing to the frame, as well as of the connections between the members of the frame were shown to have a strong effect on the simulated behaviour of shear wall units.

Regarding solid wall panels, it was concluded that walls with a high level of both stiffness and strength can be produced by use of such panels, and also that the connections between the solid wall panels can be designed in such a way that the shear forces involved are effectively transmitted from one panel to the next.

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Schroder, Ulf P. "Development of a weather radar signal simulator to examine sampling rates and scanning schemes." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2005. http://library.nps.navy.mil/uhtbin/hyperion/05Sep%5FSchroder.pdf.

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Vessby, Johan. "Analysis of shear wallsfor multi-storey timber buildings." Doctoral thesis, Linnéuniversitetet, Institutionen för teknik, TEK, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-11489.

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This doctoral thesis addresses questions of how wind loads acting on multistoreytimber buildings can be dealt with by structural design of such buildings.The conventional use of sheathing either nailed or screwed to a timberframework is considered, together with other stabilizing structures such ascross-laminated timber panels.The finite element method was employed in simulating the structuralbehaviour of stabilizing wall units. A series of studies was carried out of walls inwhich the sheathing was nailed to a timber frame. Different structural levelswere studied starting with modelling the performance of single sheathing-toframingconnections, to the use of models for studying the overall structuralbehaviour of walls. The results of calculations using models for simulation ofwalls subjected to different loading agree reasonably well with experimentalresults. The structural properties of the connections between the sheathing andthe frame, as well as of the connections between the members of the frame,were shown to have a substantial effect on the simulated behaviour of shearwall units. Both these types of connections were studied and described inappended papers.Regarding cross-laminated timber wall panels, it was concluded that walls witha high level of both stiffness and strength can be produced by the use of suchpanels, and also that the connections between the solid wall panels can bedesigned in such a way that the shear forces involved are transmitted from onepanel to the next in an efficient manner.Other topics in the thesis include the properties of connections between shearwalls and the rest of the building. Typically high tension forces occur at specificpoints in a timber structure. These forces need to be transmitted downwards inthe structure, ultimately connecting them to the substrate. A lap-joint that maybe used for this purpose has been studied using generalized Volkersen theory.Finally the maximum capacity of a conventional rail to substrate connection hasbeen examined using linear and nonlinear fracture mechanics.

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Pan, Da-Gang Lin Yeong-Jer. "Structure and evolution of a midwestern storm during VORTEX-95 as determined from airborne doppler data /." SLU electronic book. Click to access, 1999. http://proquest.umi.com/pqdweb?did=731937091&sid=1&Fmt=2&clientId=26447&RQT=309&VName=PQD.

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Wu, Peng, Xiquan Dong, Baike Xi, Yangang Liu, Mandana Thieman, and Patrick Minnis. "Effects of environment forcing on marine boundary layer cloud-drizzle processes." AMER GEOPHYSICAL UNION, 2017. http://hdl.handle.net/10150/624343.

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Determining the factors affecting drizzle formation in marine boundary layer (MBL) clouds remains a challenge for both observation and modeling communities. To investigate the roles of vertical wind shear and buoyancy (static instability) in drizzle formation, ground-based observations from the Atmospheric Radiation Measurement Program at the Azores are analyzed for two types of conditions. The type I clouds should last for at least 5h and more than 90% time must be nondrizzling and then followed by at least 2h of drizzling periods, while the type II clouds are characterized by mesoscale convection cellular structures with drizzle occur every 2 to 4h. By analyzing the boundary layer wind profiles (direction and speed), it was found that either directional or speed shear is required to promote drizzle production in the type I clouds. Observations and a recent model study both suggest that vertical wind shear helps the production of turbulent kinetic energy (TKE), stimulates turbulence within cloud layer, and enhances drizzle formation near the cloud top. The type II clouds do not require strong wind shear to produce drizzle. The small values of lower tropospheric stability (LTS) and negative Richardson number (R-i) in the type II cases suggest that boundary layer instability plays an important role in TKE production and cloud-drizzle processes. By analyzing the relationships between LTS and wind shear for all cases and all time periods, a stronger connection was found between LTS and wind directional shear than that between LTS and wind speed shear.

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Eppanapelli, Lavan Kumar. "Investigation of wind potential variation at three measurement sites based on atmospheric stability and power production." Thesis, KTH, Kraft- och värmeteknologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-136935.

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As tapping energy from wind expands rapidly worldwide, it is a common procedure to locate a practicable site to extract energy from abundant wind flow by building wind farms. Comprehensive understanding of wind resource at a site is important to perform the main activities say, wind flow modeling, wind turbines micro siting, annual energy yield calculation and cost of energy estimation. Wind measuring campaigns involve using of measuring instruments such as meteorological tower instrumented with anemometers, wind vanes and temperature sensors; remote sensing devices such as SoDAR, LiDAR. These meteorological devices provide detailed information on wind behavior with respect to the height, time and temperature. These systems were proven in providing promising wind measurements even though they are susceptible to certain weather conditions. The study progressed by focusing on the wind behavior at three locations to investigate the possible factors that varies the wind character. A location with one met mast and two AQ500 SoDAR systems was considered for this project where one AQ500 is 800m away and other AQ500 is 5515m away from the point of Met mast. The location is contemplated as a decent approach to the spatial analysis of the wind resource as there is a large scope to analyze the wind character between two nearby sites and two faraway sites. Monostatic 3-beam SoDAR systems from AQ System, Sweden and 100m meteorological tower with instruments are used in this project work for collecting the wind data. One-year worth of wind data at standard 10min intervals has been collected from the three systems. This report outlines the theoretical description of project location, AQ500 SoDAR and Met mast. A detailed explanation of the data quality control and filtering methods are discussed along with respective reasons. The conclusion is drawn after performing the statistical analysis between wind speed and other parameters such as turbulent intensity, wind direction, thermal stability and temperature. Mat lab is used for computing and analyzing the wind data from three systems.

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Pereira, Maurício Vieira da Rocha. "Impacto da altura de aerogeradores sobre a velocidade do vento, energia, efeito de esteira e intensidade de turbulência : estudos de caso em três projetos eólicos localizados no Brasil." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2016. http://hdl.handle.net/10183/134892.

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O setor eólico está em processo de consolidação no Brasil desde o início dos anos 2000, e oportunidades de pesquisas e desenvolvimento estão presentes em todas as etapas do processo. Este trabalho apresenta uma relação entre os parâmetros de velocidade do vento, energia, efeito de esteira e intensidade de turbulência com diferentes alturas de turbinas existentes no mercado brasileiro, em três regiões distintas, Triunfo/PE, São João do Cariri/PB e São Martinho da Serra/RS. A finalidade do trabalho é auxiliar os desenvolvedores e os investidores de parques eólicos na tomada de decisão sobre as alturas de aerogeradores a serem consideradas em seus projetos eólicos, antecipando a avaliação criteriosa do recurso eólico local. Para tal, primeiramente são citadas referências de trabalhos similares disponíveis na literatura bem como é realizada a fundamentação teórica do estudo com as principais equações e modelos utilizados na área. A metodologia do cálculo é teórica e aplicada às ferramentas computacionais do WAsP para a modelagem do vento e do WindFarmer para avaliar a produção de energia elétrica, com adaptações específicas para cada projeto. Procedimentos estatísticos são efetuados a fim de se garantir que as análises contenham o menor nível possível de incerteza na identificação do recurso eólico de cada região. Os resultados do trabalho são apresentados comparativamente entre os sete modelos de aerogerador testados e também entre as três áreas estudadas. O comportamento das turbinas é consideravelmente diferente em todas as opções estudadas. Os modelos de aerogerador A e D são os que apresentam o maior ganho energético percentual com o incremento da altura da turbina com valores médios de 0,42% e 0,44% a cada metro. Já os modelos C e D apresentam as melhorias mais consideráveis em termos de redução de intensidade de turbulência e diminuição de perdas por efeito de esteira, conforme se aumenta a altura das turbinas. As áreas apresentam, também, recursos eólicos distintos entre elas. O projeto eólico de Triunfo é o que apresenta a maior geração de energia dentre os estudados, sendo 24,2% maior que em São Martinho da Serra e 45,0% maior que em São João do Cariri. Verifica-se, também, que caso a velocidade média do vento de longo prazo fosse dobrada em Triunfo, a energia líquida teria um acréscimo de 88%. Já em São Martinho da Serra este valor chegaria em 170% e em São João do Cariri em 220%.
The wind energy sector has been under consolidation in Brazil since the early 2000s. Opportunities for researches and developments are present at all stages of the process. This paper presents a link among wind speed, energy, wake effect and turbulence intensity parameters and the height of existing wind turbine models in Brazil, considering three distinct regions as Triunfo/PE, São João do Cariri/PB and São Martinho da Serra/RS. This paper also aims to support developers and investors in the decision making process in the wind turbines height that should be considered in its wind farms. To this end, the references of similar studies as well as the theoretical basis for the study, including the main equations and models, are presented. The calculation methodology is theoretical and it has been applied to the computational tools WAsP (wind modeling) and WindFarmer (evaluate the energy production), considering specific adaptations for each project. Statistical procedures are performed in order to ensure that the analyses contain the lowest possible level of uncertainty in the characterization of the wind resources in each region. The results are presented comparatively among the seven tested turbine models and also among the three studied areas. The turbine models behavior is considerably different for all options. The wind turbine models A and D are those with the highest percentage energy increase with increasing the turbine height. Their average values are 0.42% and 0.44% per meter height. The models C and D present the most considerable improvements in terms of turbulence intensity and wake effect reductions with increasing the turbine height. The different locations also present distinguished wind resources among them. Triunfo wind farm is the one with the highest energy generation, 24.2% higher than in São Martinho da Serra and 45.0% higher than in São João do Cariri. It is also noted that if the long term mean wind speed was doubled in the project locations, the energy would have an increase of 88% in Triunfo, 170% in São Martinho da Serra and 220% in São João do Cariri.

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Russell, Frances Marion. "Semi-permanent zones of radar radial shear within the planetary boundary layer : observations and effects on high intensity precipitation in the wider Auckland region, New Zealand : a thesis submitted to the Victoria University of Wellington in partial fulfilment of the requirements for the degree of Master of Science in Geophysics /." ResearchArchive@Victoria e-Thesis, 2009. http://hdl.handle.net/10063/1215.

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Milbank, Juliette, and milbank@turbulenflow com au. "Investigation of fluid-dynamic cavity oscillations and the effects of flow angle in an automotive context using an open-jet wind tunnel." RMIT University. Aerospace, Mechanical & Manufacturing Engineering, 2005. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20090723.121800.

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Aeroacoustic whistles are a significant source of customer complaints to automotive manufacturers. Whistles can occur on many such components, but the relative position and configuration of rearview mirrors means they are a more problematic source of tonal noise on vehicles. The low subsonic complex turbulent flow, combined with small cavity scales, determines the possible whistle mechanisms. The one considered to be most problematic, fluid-dynamic cavity resonance, is the topic of this research thesis. The research scope is limited to the automotive environment of external rearview mirrors and the fluid-dynamic resonance mechanism: low subsonic Mach number, M = 0.05 - 0.13; laminar boundary layers; and two-dimensional, acoustically compact cavities. The low unit-cost of rearview mirrors and the desire to have simple identification and prediction schemes, that could be used by production engineers, determined an empirical approach. A search of the existing literature revealed that there were some data on cavities of the above scale in low Mach number flow, but quoted errors in empirical descriptions were large and there was very little research on the effects of flow yaw angle on the chosen resonance mechanism. The research therefore aims to determine whether existing empirical descriptions of fluid-dynamic cavity resonance are suitable for the prediction of the resonance characteristics, with sufficient accuracy to enable unambiguous identification of the presence of the resonance and its mechanism. A second aim is to investigate the effects of a feature of the automotive flow environment, flow yaw angle, on the resonance. Flow yaw angle is determined by those components of the flow in the same plane as the surface in which the cavity is situated. An experimental program was undertaken using a purpose-built aeroacoustic wind tunnel and a simple cavity model. Testing with two types of cavity configurations, as well as flow visualisation, investigated the main features of the resonance in time-averaged yawed flow. Within the scope of this thesis, it is shown that fluid-dynamic cavity resonance characteristics can be accurately identified by a simple empirical model, even in yawed flow. Various descriptors allow identification of the resonance threshold, stage, frequency and relative amplitude in non-yawed flow, while the frequency and stage can also be identified in yawed flow. The relative decrease in resonance amplitude in yawed flow, although identified for these experiments, would depend on the degree of spanwise variation in the boundary layer characteristics for a given cavity configuration. The results also identify significant issues with testing in a free jet tunnel, due to the nature of fluid-dynamic cavity resonance and the fluctuation energy content in free shear layers. Despite this, the thesis aims are achieved, and appropriate design guidelines are produced for automotive designers.

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Mauk, Rachel Grant. "Tropical Cyclone Formation in Environments with Cool SST and High Wind Shear over the Northeastern Atlantic Ocean (1975-2005)." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1275445016.

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He, Yuxin. "Crop residue management and its impacts on soil properties." Diss., Kansas State University, 2015. http://hdl.handle.net/2097/19043.

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Doctor of Philosophy
Agronomy
DeAnn R. Presley
Crop residue removal for livestock feeding and biofuel production at large scales must be evaluated to assess impacts on soil productivity and properties. Among all the potential negative impacts, wind erosion is a major concern in the central Great Plains. We conducted an on-farm study from 2011 to 2013 by removing crop residue at five levels (0, 25, 50, 75, and 100%) to determine the effects of crop residue removal on soil wind erosion parameters such as dry aggregate size distribution including soil wind erodible fraction (EF <0.84 mm aggregates), geometric mean diameter (GMD) and geometric standard deviation (GSD), dry aggregate stability, and soil surface roughness. The sub-model of Wind Erosion Prediction System (WEPS) developed by the USDA-ARS, Single-event Wind Erosion Evaluation Program (SWEEP) is a stand-alone companion software package that can be applied to simulate soil loss and dust emission from a single windstorm event. We applied measured data (i.e. EF, GMD, GSD, and roughness) to SWEEP for predicting wind velocity that can initiate wind erosion and soil loss under each crop residue removal condition with wind velocity at 13 m sˉ¹. The threshold wind velocity to initiate wind erosion generally decreased with increase in crop residue removal levels, particularly for residue removal >75%. The total amount of soil loss in 3 hours ranged from about 0.2 to 2.5 kg mˉ² and depends on soil condition and crop residue cover. On the other hand, high-yielding crops can produce abundant crop residue, which then raises the question that if a farmer wants to reduce residue, what could they do without removing it? The application of fertilizer on crop residue to stimulate microbial activity and subsequent decomposition of the residue is often debated. We conducted wheat straw decomposition field experiments under different fertilizer rates and combinations at three locations in western Kansas following wheat harvest in 2011 and 2012. A double shear box apparatus instrumented with a load cell measured the shear stress required to cut wheat straw and photomicrography was used to measure the cross-sectional area of wheat straw after shearing. Total C and N were also analyzed. The fertilizer rate and timing of application during summer 2012 and Fall 2013 at the Hays site had impacts on wheat straw shear stress at break point. Across site years, earlier (fall) fertilizer application generally resulted in lower remaining aboveground biomass as compared to a spring application. Multivariate and linear regressions suggested that N and C:N ratio partially explain the results observed with respect to treatment effects on winter wheat residue decomposition.

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Kunwar, Sushil. "Comprehensive Evaluation of Composite Core Walls for Low-Seismic Force and Wind Load Applications." University of Cincinnati / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1613750905724949.

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OLIVEIRA, Gabrielle Bezerra. "Análise de padrões temporais da dinâmica do vento associadas ao ambiente de formação das linhas de instabilidade amazônica." Universidade Federal de Campina Grande, 2017. http://dspace.sti.ufcg.edu.br:8080/jspui/handle/riufcg/1757.

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Submitted by Emanuel Varela Cardoso (emanuel.varela@ufcg.edu.br) on 2018-09-19T20:06:03Z No. of bitstreams: 1 GABRIELLE BEZERRA OLIVEIRA – DISSERTAÇÃO (PPGMet) 2017.pdf: 2219344 bytes, checksum: b1c40baaf11a5f1e293aa66cdc9139b9 (MD5)
Made available in DSpace on 2018-09-19T20:06:03Z (GMT). No. of bitstreams: 1 GABRIELLE BEZERRA OLIVEIRA – DISSERTAÇÃO (PPGMet) 2017.pdf: 2219344 bytes, checksum: b1c40baaf11a5f1e293aa66cdc9139b9 (MD5) Previous issue date: 2017-02-24
CNPq
O enfoque deste trabalho é contribuir para a compreensão dos mecanismos responsáveis pela formação das Linhas de Instabilidade Tropicais da Amazônia. Analisou-se 3 anos de dados de reanálises investigando as características dinâmicas dos perfis verticais do vento zonal e meridional a partir da média do período e das médias trimestrais dos dias com e sem a formação de LI. Mostrou-se que o JBN é uma característica intrínseca do ambiente amazônico, entretanto nos dias com a formação de LI esse jato é mais intenso e profundo. Os trimestres março-abril-maio e junho-julho-agosto não apresentam um JBN bem definido, principalmente em relação à sua profundidade. Destaca-se ainda que o cisalhamento vertical do vento é mais intenso nos dias com a formação de LI. Já o maior cisalhamento direcional da componente meridional do vento é visto nos perfis dos dias sem LI. Para auxiliar o entendimento da variabilidade temporal dos perfis verticais do vento foi aplicada a técnica de Análise Fatorial em Componentes Principais com o intuito de investigar a existência de padrões atmosféricos associados à ocorrência de LI. As três primeiras componentes principais da componente zonal do vento explicaram aproximadamente 89% da variância total dos dados, enquanto que os 93% da variância total da componente meridional foi explicado pelas cinco primeiras componentes principais. A análise dos padrões temporais associados a cada fator sugere que os trimestres DJF e SON são influenciados pela variação sazonal da ZCIT e os trimestres MAM e JJA pela ASAS e DOL.
The aim of this work is to contribute to the understanding the mechanisms responsible for the formation of Amazon Tropical Squall Lines (ASL). 3 years of reanalysis data were analyzed investigating the dynamic characteristics of vertical profiles of the zonal and meridional wind from the a average of period and quarterly of the days with and without the ASL formation. It has been shown that low level jet (LLJ) is an intrinsic characteristic of Amazonian environment, however in the days with the formation of SL this LLJ is more intense and deep. The quarters March-April-May and June-July-August do not present a well defined LLJ, mainly in relation their depth. It was also pointed out that vertical shear of wind is more intense on days with ASL formation. However, the greatest directional shear of meridional component wind is seen in the profiles of days without ASL. To aid the understanding of temporal variability of vertical profiles wind were applied the method Principal Components Fatorial Analysis in order to investigate the existence of atmospheric patterns associated with the occurrence of ASL. The first three Principal Components of the zonal wind component explained approximately 89% of the total variance of the data, while the 89% of the total variance of the meridional wind component were explained by the first five principal components. The analysis of the time patterns associated with each factor suggests that the DJF and SON quarters are influenced by the seasonal variation of the ITCZ and the quarters MAM and JJA by South Atlantic Subtropical High (SASH) and Easterly Wave Disturbances (EWD).

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Woldemikael, Biruk Worku. "Effects of cracking of coupling beams onhigh rise towers subjected to wind load." Thesis, KTH, Betongbyggnad, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-290589.

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In high rise towers, reinforced concrete elevator shafts with coupling beams are extensively used as a principal structural element to resist lateral loads. The lateral load resistance of the tower is dominantly dependent on the stiffness of the load-bearing walls, and coupling beams connecting them. In an interest to study the reduction in the stiffness of high rise tower due to cracking in the coupling beams, variability in the reinforcement content, concrete grade and the effect of joint flexibility at the beam-wall intersection, this master thesis presents the analytical and finite element approaches to determine the equivalent height of the concrete coupling beams and the overall global stability of the high-rise tower. A comprehensive parametric study on 240 combinations of reinforced concrete coupling beams and 48 models of the global tower has been carried out to backtrack the effective stiffness of the RC coupling beams from the load-deflection curve. As a result, the stiffness and the equivalent height of coupling beams are computed and plotted as a function of the concretegrade, reinforcement content and aspect ratio. Additionally, the tip deflections of the towers for both the cracked & reinforced and un-reinforced & un-cracked models are also plotted as functions of the concrete grade, reinforcement content and aspect ratio.The obtained results show that the stiffness ratio and the ratio of the equivalent height to the normal height increase with the increase in the longitudinal reinforcement ratio and aspectratio but decrease with an increase in the concrete grade for both analytical and finite element methods. The tip deflection of tower is not significantly affected by an increase in the reinforcement content of slender coupling beams and vice versa for both the analytical and the finite element method. Independently of the slenderness of the composing coupling beams, the stiffness increases significantly with an increase in the concrete grade. These results show a good picture on how to choose the equivalent height in the model with no reinforcement. So, the developed diagram will be a more practical method for the designer of awhole building at the early stage design. Thick coupling beams need to be reinforced to reach the gross section’s stiffness while slender sections will have a higher stiffness with reinforcement. This would help the designer to find a more rational model without reinforcement. Using Hans Petersson’s analytical method, regarding the joint flexibility at the beam wall intersection, to exploit the full capacity of a concrete coupling beam section, the stiffness should be reduced. For global models, independently of the slenderness of the composing coupling beams, the stiffness increases significantly with an increase in the concrete grade.
I höghus används hisschakt av armerad betong tillsammans med kopplingsbalkar i stor utsträckning som främsta konstruktionselement för att motstå horisontella laster. Tornets horisontella bärförmåga är beroende av analytiska studier och studier med finita element metoden styvheten hos de bärande väggarna, och kopplingsbalkarna som förbinder dem. För att studera minskningen av styvheten i höghustorn på grund av sprickbildning i kopplingsbalkar, variationen i armeringsmängden, betongkvaliteten och effekten av ledflexibilitet vid balk-vägg-knutpunkten, presenterar detta examensarbete kopplingsbalkarnas effektiva styvhet och höghusets globala stabilitet. En omfattande parametrisk studie på 240 olika kombinationer av armerade kopplingsbalkar och 32 modeller av ett höghus har genomförts för att härleda den effektiva styvheten i de armerade kopplingsbalkarna från last-deformationskurvan. Som ett resultat beräknas styvheten och den ekvivalenta höjden av kopplingsbalkarna och plottas som funktion av betongkvaliteten och armeringsmängden. Dessutom modelleras höghuset för både spruckna & armerade kopplingsbalkar samt oarmerade & ospruckna kopplingsbalkar för att erhålla utböjningen av höghusets topp. Resultatet plottas som funktion av betongkvaliteten och armeringsmängden. De erhållna resultaten visar att styvhetsförhållandet och förhållandet mellan ekvivalent höjd till normal höjd ökar med mer längsgående armering och tvärsnittsförhållandet men minskar med en ökning av betongkvaliteten för både den analytiska och finita elementmetoden. Utböjningen av höghusets topp påverkas inte nämnbart av en ökning av armeringsmängden i de slanka kopplingsbalkarna och vice versa för både den analytiska och finita elementmetoden. Oberoende av slankheten av kopplingsbalkarna ökar styvheten betydligt med en ökning av betongkvaliteten. Dessa resultat visar en bra bild på hur man väljer ekvivalent höjd i modellen utan armering. Därmed kommer det framtagna diagrammet vara en mer praktisk metod för att i ett tidigt skede konstruera en hel byggnad. Tjocka kopplingsbalkar måste armeras för att nå tvärsnittets styvhet medan smala tvärsnitt kommer att ha en högre styvhet med armering. Detta skulle hjälpa konstruktören att hitta en mer rationell modell utan armering. Med hjälp av Hans Peterssons analytiska metod, angående ledflexibiliteten vid balk-väggknutpunkten, bör styvheten minskas för att utnyttja den fulla kapaciteten hos en betongkopplingsbalk. För globala modeller, oberoende av de slanka kopplingsbalkarna, ökar styvheten betydligt med en ökning av betongkvaliteten.

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Fytterer, Tilo, Christina Arras, and Christoph Jacobi. "Terdiurnal signatures in midlatitude sporadic E layers occurrence rates." Universität Leipzig, 2013. https://ul.qucosa.de/id/qucosa%3A16409.

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Global Positioning System radio occultation measurements by the FORMOsa SATellite mission-3/Constellation Observing System for Meteorology, Ionosphere and Climate satellites were used to analyse the behaviour of the signature of the terdiurnal tide in sporadic E (ES) layers at midlatitudes (43°N – 63°N). According to theory, the occurrence of ES is expected when the vertical zonal wind shear, which is mainly owing to solar tides, is negative. 4-year means, based on 3-monthly running mean zonal means from December 2006 - November 2010, were constructed for the terdiurnal oscillation in the occurrence frequency of ES. Comparison of the results with VHF meteor radar observations of the terdiurnal tide and the 8-hr oscillation in the vertical zonal wind shear at Collm, Germany (51.3°N, 13°E) shows a clear correspondence between the 8-hr Es and wind shear signature.
Radiookultationsmessungen auf der Basis von GPS-Messungen der FORMOsa SATellite mission-3/Constellation Observing System for Meteorology, Ionosphere and Climate-Satelliten wurden verwendet, um die Signatur der 8-stündigen Gezeiten in den Auftrittsraten von sporadischen E (Es)-Schichten zu analysieren. Nach der allgemein anerkannten Windscherungstheorie treten Es-Schichten im Bereich negativer vertikaler Windscherung auf, welche in der unteren Thermosphäre hauptsächlich durch solare Gezeiten hervorgerufen werden. Speziell werden hier 4-jährige Mittelwerte saisonal gemittelter Auftrittsraten untersucht um die 8-stündige Signatur zu finden. Ein Vergleich mit Radarmessungen des Windes über Collm zeigt, dass die saisonale und tägliche Variabilität der 8-stündigen Komponente der Es-Raten sehr gut mit derjenigen der gemessenen Windscherung übereinstimmt.

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Memon, Muhammad Omar. "Wingtip Vortices and Free Shear Layer Interaction in the Vicinity of Maximum Lift to Drag Ratio Lift Condition." University of Dayton / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1492701624726378.

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Sementi, Joshua Paul. "A study of jet exhaust-wing interaction /." Thesis, Connect to this title online; UW restricted, 2005. http://hdl.handle.net/1773/10002.

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Bennaceur, Iannis. "Etude numérique de la diffusion d'une onde acoustique par une couche de cisaillement turbulente à l'aide d'une simulation aux grandes échelles." Thesis, Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0187/document.

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Lors des mesures acoustiques dans les souffleries à veine ouverte, les ondes acoustiques émises par une maquette ou une source située dans la veine se propagent dans la couche de cisaillement turbulente qui se forme aux abords du jet avant d’être reçues par les microphones localisés en dehors. L’onde acoustique interagit avec le champ de vitesse turbulent de la couche de mélange ce qui a pour effet de modifier son contenu spectral, de redistribuer spatialement son énergie et de moduler sa phase et son amplitude, on parle alors de diffusion acoustique. Cette thèse a consisté à l’étude de la diffusion d’une onde acoustique par une couche de cisaillement turbulente à l’aide d’une simulation numérique aux grandes échelles. Pour cela, il a d’abord été nécessaire de réaliser la simulation numérique aux grandes échelles d’une couche de cisaillement turbulente plane dans son régime auto-similaire. Dans un second temps, nous avons simulé l’interaction entre une onde acoustique et l’écoulement turbulent afin d’étudier les caractéristiques du champ de pression diffusé qui en résulte. Nous avons notamment vérifié que la simulation était capable de prédire précisément les fréquences sur lesquelles est répartie la plupart de l’énergie acoustique ainsi que la forme du spectre de pression diffusé. Finalement, le champ de vitesse du milieu turbulent qui est corrélé avec l’enveloppe du champ de pression diffusé a été reconstruit à l’aide de la méthode de l’estimation stochastique linéaire. Cette méthode nous a notamment permis de visualiser les larges structures turbulentes qui interviennent principalement dans le mécanisme de diffusion acoustique
During open jet wind tunnel measurements, the acoustic waves emitted by a device or an acoustic source located inside the flow propagate inside the turbulent shear layer that develops at the periphery of the jet before being received by microphones located outside the flow. The acoustic wave interacts with the turbulent velocity field leading to a change of directivity, a phase and amplitude modulation as well as a spectral re-distribution of the acoustic energy over a band of frequencies. This phenomenon is known as acoustic scattering. This work has consisted in the study of the scattering of an acoustic wave by a turbulent shear layer using large-eddy simulation. The first step of the study has consisted in the large-eddy simulation of a turbulent shear layer in its self-similar state. In a second second step, the direct computation of the interaction between the acoustic wave and the turbulent flow has been performed in order to study the characteristics of the resulting scattered pressure field. It has been shown that the numerical simulation is able to accurately predict the frequencies on which the main part of the scattered energy is redistributed, as well as the shape of the scattered pressure spectrum. Finally, the turbulent velocity field which is correlated with the envelope of the scattered pressure field is reconstructed using the linear stochastic estimation method. This method has enabled the visualization of the large turbulent structures that mainly take part in the acoustic scattering mechanism

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Kuo, Matthew Yih-Han. "Deep ocean clay crusts : behaviour and biological origin." Thesis, University of Cambridge, 2011. https://www.repository.cam.ac.uk/handle/1810/240506.

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In water depths of 500m to greater than 2,000m, off the West coast of Africa, sediments comprise very soft clays with extremely high water contents and plasticity. In situ CPT and T-bar testing in these areas have identified 'crusts' with undrained shear strengths of up to15kPa at 0.5m depth, before the strength reduces by an order of magnitude to normallyconsolidated strengths by 2m depth. This thesis presents an investigation into the behaviour and origin of these crusts. Mini ball-penetrometer tests on natural cores confirm the crustal strength, and indicate a sensitivity of 3 within the crust. However, pipeline interface tests using the Cam-shear device demonstrate a significant variability in the measured interface friction coefficient. Particularlylow strengths are observed when shearing in an undrained manner on a rough interface. These results are attributed to the heterogeneity of natural samples, and demonstrate the need to better understand the origin of the crust material in relation to interface micro-mechanics. A microbiological investigation of crust material by extracting bacteria DNA from claysamples is described, and identifies the presence of the bacterium, Marinobacter aquaeolei. This bacterium is then used to inoculate sterile samples to determine its ability to produce crustal strength. Through this work, it is concluded that M. aquaeolei is unable to create crustal strength, although extracelluar polysaccharides produced by this bacterium will influence thepermeability of sediments through the clogging of voids. It is therefore also concluded that future geotechnical investigation into marine sediments should consider the presence of bacteriaand their ability to influence the soil properties. Wet sieving of crust material shows that the crust comprises a mixture of burrowing invertebrate faecal pellets and clay. Pellets are found to represent 20% to over 55% of the crust material by dry mass. Individual pellets are shown to exhibit unconfined compressive strengths of between 5kPa and 50kPa, thus demonstrating their strength and robustness. Consolidationbehaviour is governed by the percentage of pellets in natural samples. Based ontheir location, abundance and strength, it is concluded that the origin of crustal strength lies with the presence of burrowing invertebrate faecal pellets. When sheared on rough pipeline interfaces, however, pellets are observed to crush, expelling void-filling fragments that may generatepositive excess pore pressures. Smeared clay produced when shearing natural samplesobstructs the dissipation of pore pressures, which may encourage hydroplaning, and explainthe observation of very low interface friction coefficients. It is therefore suggested that smooth pipelines offer more sliding resistance by minimising the risk of pellet crushing. This thesis proposes that wet sieving of core samples should be undertaken during the site investigationsfor future deep-water, hot-oil pipeline installations to provide design information on both the consolidation and strength behaviour of natural sediments.

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Chemlali, Alexander, and Rickard Norberg. "Shear cracks in reinforced concrete in serviceability limit state." Thesis, KTH, Betongbyggnad, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-169591.

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Shear cracks are formed when high oblique tensile stresses, e.g. in thin webs, exceed the tensile strength. A known example of this phenomenon is the extensive shear cracks that were found on the box-girder bridges Gröndal and Alvik, which were mainly caused by insuﬃcient amount of shear reinforcement. In order to avoid this incident (inadequate amount of shear reinforcement), the reinforcement stress is often being assumed as a ultimate limit load in order to fulﬁll requirements regarding crack control in the service-ability limit state (SLS). This method has led to a overestimation of the reinforcement amount in bridge-design. The aim of this master thesis is therefor to study the shear crack phenomenon and investigate if the amount of shear reinforcement in bridges can be reduced. The ﬁrst part of this thesis studies the shear cracking behavior in concrete in a plane stress state, while the second part focus how design standards as well as manuals treats shear cracks. Shear cracking in the reinforced concrete panels has been studied with non-linear ﬁnite element analysis and compared to experimental testings performed by the University of Toronto. Three diﬀerent loading conditions for the panels has been analyzed: pureshear, compression or tension combined with shear. The panels are to represent parts of a web in a box-girder bridge that are subjected to in-plane stresses. The non-linear ﬁnite element analysis was performed in the FE-program Atena where mainly the crack propagation and crack pattern were studied. The material model in Atena is a smeared crack model with either ﬁxed or rotated crack direction. The panel analysis, in SLS, gave various results. For loading conditions pure shear and tension/shear, the response of the FE-analysis gave a similar result regarding crack pattern but diﬀered in size of crack width. For compression/shear, only micro-cracks developed and did not reﬂect the result from the real panel tests. This may be the consequence of a too stiﬀ FE-model and the fact that, in the real tests, some cracks occurred due to out-of-plane bending. With methods described in Eurocode 2 and the Swedish handbook for EC2, a shear crack calculation model was created in order to determine the reinforcement stress and crack width. As a reference for the shear crack calculations, a wing structure (1 m strip) has been used which is part of a railway bridge located in Abisko. These calculations were done in order to investigate if the amount of shear reinforcement could be reduced and at the same time fulﬁll crack control demands in SLS. The bridge department at Tyréns AB concluded, according to a truss model, that the wing section should be reinforced with a amount of 14.1 cm2/m2 while our model showed that the crack width demand could be fulﬁlled with a equivalent amount of 9.82 cm2/m2, i.e. a reduction around 30%.

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37

Novozámský, Adam. "Střih větru jako nebezpečný jev v letectví." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2014. http://www.nusl.cz/ntk/nusl-231313.

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This thesis is about wind shear and its influence on aviation. There is wide theoretical description of wind shear and it’s implemented into aviation practice. There are also methods of observation, forecasting and reporting, for both pilots and meteorologist described. In this thesis, pilots can find useful recommendations for dealing with wind shear during the flight. Every reader can also read about famous aviation accidents and look at models of weather that caused those accidents. At the end of thesis there are analyses of a rawiosonde measurements related to wind shear reports. This whole thesis is focused on increasing awareness of wind shear in aviation from angle of view of both pilots and aviation meteorologist.

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Fabiánová, Lucie. "Přepočet a variantní návrh nosných konstrukcí objektů administrativního centra." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2014. http://www.nusl.cz/ntk/nusl-226643.

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The aim of this thesis was to develop assessments of existing supporting structure of a rectangular object and design of new options for rectangular and cylindrical object administrative center in the Jihomoravská plynárenská, a.s. in Brno. According to the task have been recalculated construction and design of new structures in accordance with applicable standards. New design of both buildings (rectangular and cylindrical) came from several studies.

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Tomala, Daniel. "Návrh letounu podle předpisu FAR 103." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2008. http://www.nusl.cz/ntk/nusl-227917.

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This diploma work considers conceptual design of aircraft in accordance in FAR 103 regulation. On the base of statistical dates has been made basic geometrical and aero-dynamical concept of a single occupant aircraft. For conception have been chosen optimal driving force and bases calculations of the load pressure and dimensions are included.

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Hong, Wei_Chuan, and 洪偉川. "Flight Path and Wind Field Reconstruction in Wind Shear Flow." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/35240381464274118558.

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碩士
國立成功大學
航空太空工程學系碩博士班
94
The objective of this research is to reconstruct the wind field and the flight path for aircraft in wind shear flow encounter. Wind field experienced by the flying aircraft is generated by a microburst mathematical model and the aircraft position. Two-step method is introduced, in which the Genetic Algorithm is used in conjunction with the Extended Kalman Filter to identify the system error parameters and to estimate the state variables. The first-step identification uses flight data obtained in smooth air, whereas the second-step assumes the error factors associated with the air data are invariant when analyzing the flight data in turbulence. The objective function is derived using the Maximum Likelihood principle, and the system error parameters are obtained by optimizing this objective function. The use of Genetic Algorithm aims to solve the numerical stiffness and the initial guess problems associated with the gradient search methods. In this research a Boeing 747-100 airplane encountered with 3 different wind shear fields during approaching are simulated. The results of constant bias and scale factors estimated by the present Genetic Algorithm were satisfactory. The state variables and flight paths and the wind shear fields are successfully reconstructed, indicating the appropriateness of applying the present method to wind shear flight data analysis.

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Wu, Jia-Hong, and 吳嘉鴻. "Resiliency of Concentric Eyewall Vortex against Vertical Wind Shear." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/50772562761376763354.

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碩士
國立臺灣大學
大氣科學研究所
95
This study, with the aid of two-layer shallow water model, explore the vortex resiliency of concentric eyewall against vertical wind shear. In particular, we focus on (1)moat width ; (2)outer eyewall width ; and (3)intensity parameters on the vortex. The resiliency ability against the vertical wind shear is defined as a ratio in compare to the control run(radius=100km; intensity = Zc=1.8e-3s-1 ) which shows “tilt-align” in vertical structure when vertical wind shear reach the maximum(Uc=11m/s). The result shows both intensity and structure of concentric vortex are important factors for vortex resiliency against vertical wind shear. The numerical simulations indicate that: (1)vertical wind shear destroys the concentric eyewall structure in most of the cases simulated, (2)vortex resiliency of concentric eyewall vortex is weaker than the similar non-concentric eyewall counterpart, (3)vertical resiliency decreases with the increase of the baroclinicity of the concentric vortex, (4)vortex resiliency against vertical wind shear increases with the intensity of the core vortex, (5)other parameters being equal, the vortex resiliency increases with the increase of outer eyewall circulation, (6)other parameters being equal, the vortex resiliency decreases with the increase of outer eyewall width, and (7)other parameters being equal, the vortex resiliency decreases with the increase of moat width.

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Yu, Cheng-Da, and 余政達. "Study on Particle Continuous Saltation Mechanism under Wind Shear." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/53284431880911917446.

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碩士
國立交通大學
土木工程系
91
Under wind shear, the particle motion of soil on the surface including the particle suspension, saltation and surface creeping, in which saltation is the key factor, results in the landform erosion. The powerful dropping thrust of particles is the main factor for the cause of the aeolian sand motion and the landform erosion. The wind tunnel experiment is conducted to visualize and analyze the particle saltant motion. To measure the motion orbit, motion speed, and the collision angle of the particle continuous saltant process under different wind velocity the high speed photographic technique is applied. Based on the observed data, the physical phenomenon and the statistical characteristics for the particle motion are explored. In the sequence 2-D mathematical model of particle continuous saltation is established. The particle continuous saltation model established in this study includes two parts: the single-step saltant model and the collision model. The simulation results reveal that the trajectory and saltant characteristics can be interpreted under the given conditions of the ejection velocity and the size of particle. Moreover, from the analysis and find that the inter-particle collision behavior not only follows the Newton’s laws but also is controlled by random processes. Finally, the confidence level for the average saltant length and height is compared with the experimental data, showing that the proposed model is able to simulate the particle continuous saltation reasonably.

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43

Wong, Wai-Mun, and 黃偉民. "Numerical Analysis of Wind Shear Effect in Spin Coating." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/39668584916337359438.

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碩士
國立中央大學
機械工程學系
85
The process of spin coating has been extensively studied. However,to our knowledge, all studies related has either neglected or just appliedCochran's solution for the shear stress at the interface between the over-lying gas and the film surface. It is suitable when applied to a spin coaterunder free space and an infinite disk. However, for a real model where thereis an enclosure or a hub and a finite radius is taken into account, shearstress may differ from that of Cochran's solution. This study intends to in-investigate the effect of the enclosure, as well as, a hub on the shear stress . Results show the distribution of shear stress along the disk may not alike that of Cochran's solution, and may have to be re-evaluated.

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44

Gallina, Gregory M. "Environmental vertical wind shear and tropical cyclone intensity change utilizing enhanced satellite derived wind information." 2002. http://catalog.hathitrust.org/api/volumes/oclc/50084050.html.

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Thesis (M.S.)--University of Wisconsin--Madison, 2002.
Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 78-79).

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45

Meanor, Denis H. "Vertical wind shear as a predictor of tropical cyclone motion." Thesis, 1987. http://hdl.handle.net/10945/22846.

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46

Wang, Shiang-Yi, and 王翔儀. "Effects of the Vertical Wind Shear on Tropical Cyclone Intensity." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/53601267731961381204.

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47

Talgo, Kevin D. "Tropical Atlantic vertical wind shear variability in a future climate." 2009. http://www.lib.ncsu.edu/theses/available/etd-10302009-105719/unrestricted/etd.pdf.

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48

Chieh-JuJuan and 阮婕如. "System Analysis and Alert for Real Time Airport Wind Shear Detection." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/c4756w.

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碩士
國立成功大學
航空太空工程學系碩士在職專班
104
Low level wind shear has been recognized as a serious hazard to aviation safety, especially when it occurs during aircraft take-offs and landings. In these flight phases, the aircraft flight altitude and airspeed are approaching to their critical margin. The sudden variation of wind speed and wind direction may affect aircraft performance greatly. Pilots’ misjudge or retardation may bring aircraft into catastrophic states. Low level wind shear and small-scale microburst detection over the runway or within 3 nautical miles on both direction extensions may find some effective early warning signals to pilots. A simple barometric data detection system is proposed and established in Sung-Shan Airport to collect atmospheric pressure changes in real time and convert the statistical micro-changes to identify the wind burst. This thesis uses the barometric data of an established system to analyze the ground atmospheric pressure changes along runway. Based on the collected weather data, the fluctuation and standard deviation of the barometric pressure changes are calculated and detected. When the time span and frequency of the weather parameters exceed one statistics sigma, the correlated wind shear alert will be alarmed from the ground station. The analytical results demonstrate the effectiveness of the proposed detection mechanism to enforce aviation safety.

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Krallis, George A. "Modeling the mean shear component of wind-induced mixing in lakes /." Diss., 2000. 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:9982866.

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Chen, Kuan-Ting, and 陳冠廷. "Climatology of ionospheric Sporadic E Layer : Examination of Wind Shear Theory." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/10140004731560594998.

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碩士
國立中央大學
太空科學研究所
101
On the basis of GPS radio occultation (RO) technique, we develop a method to extract ionospheric sporadic E (Es) layer from COSMIC-measured ionospheric data (e.g., GPS signal signal-to-noise ratio, L1 and L2 excess phases and RO-retrieved electron density) to investigate the climatology of the Sporadic E layer. The results show that there is salient summer-winter asymmetry in the occurrence rate of the Es layer, namely, higher in summer hemisphere and lower in winter hemisphere. In addition, there is a strong tendency for the Es layer to descend with local time that is in harmony with the diurnal or semi-diurnal tidal motion, depending on season and latitude region. In order to realize the physical process responsible for the climatology of the COSMIC-measured Es layer, we simulate the temporal and global distribution of the occurrence of the Es layer in accordance with wind shear Theory. We calculate vertical ion drift velocity based on empirical models of the ionosphere, including HWM07, MSIS00, IGRF. The ferric ion (Fe+) density calculated from Whole Atmosphere Community Climate Model(WACCM) is used to obtain ferric ion vertical flux. The simulation results show that the seasonal asymmetry of the Sporadic E layer occurrence rate between the summer and winter hemispheres is very likely caused by the neutral wind shear in the Es region.

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Dissertations / Theses on the topic 'Wind shear'

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