Dissertations / Theses: 'Wind turbines Mathematical models'

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Scott, Ryan. "Characterizing Tilt Effects on Wind Plants." PDXScholar, 2019. https://pdxscholar.library.pdx.edu/open_access_etds/5035.

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Tilting the nacelle of a wind turbine modifies entrainment into the wind plant and impacts total efficiency. Extreme angles can produce flying and crashing wakes where the wake either disrupts entertainment from the undisturbed flow above or is decimated on the ground. The effect of tilt angle on downstream wake behavior was investigated in a series of wind tunnel experiments. Scale model turbines with a hub height and diameter of 12 cm were arranged in a Cartesian array comprised of four rows of three turbines each. Nacelle tilt was varied in the third row from -15° to 15° in chosen 5° increments. Stereo PIV measurements of the instantaneous velocity field were recorded at four locations for each angle. Tilted wakes are described in terms of the average streamwise velocity field, wall-normal velocity field, Reynolds stresses, and mean vertical transport of kinetic energy. Conditional sampling is used to quantify the importance of sweep vs. ejection events and thus downwards vs. upwards momentum transfer. Additionally, wake center displacement and changes in net power are presented and compared to existing models. The results demonstrate large variations in wake velocity and vertical displacement with enhanced vertical energy and momentum transfer for negative tilt angles. Simulation models accurately predict wake deflection while analytic models deviate considerably highlighting the difficulties in describing tilt phenomena. Negative angles successfully produce crashing wakes and improve the availability of kinetic energy thereby improving the power output of the wind plant.

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Fernando, Mahamarakkalage Saman Udaya Kumar. "On the performance and wake aerodynamics of the Savonius wind turbine." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/27299.

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The objective of the thesis is to establish methodology for development of a wind turbine, simple in design and easy to maintain, for possible application in developing countries. To that end the Savonius configuration is analyzed in detail both experimentally and analytically to lay a sound foundation for its performance evaluation. Following a brief review of relevant significant contributions in the field (Chapter I), an extensive wind tunnel test-program using scale models is described which assesses the relative influence of system parameters such as blade geometry, gap-size, overlap, aspect ratio, Reynolds number, blockage, etc., on the rotor output. The parametric study leads to an optimum configuration with an increase in efficiency by around 100% compared to the reported efficiency of ≈ 12 — 15%. Of particular interest is the blockage correction procedure which is vital for application of the wind tunnel results to a prototype design, and facilitates comparison of data obtained by investigators using different models and test facilities. With the design and performance results in hand, Chapters III — VI focus attention on analytical approaches to complement the test procedure. Using the concept of a central vortex, substantiated by a flow visualization study, Chapter III develops a semi-empirical approach to predict the rotor performance using measured stationary blade pressure data. The objective here is to provide a simple yet reliable design tool which can replace dynamical testing with a significant saving in time, effort, and cost. The simple approach promises to be quite effective in predicting the rotor performance, even in the presence of blockage, and should prove useful at least in the preliminary design stages. Chapter IV describes in detail a relatively more sophisticated and rigorous Boundary Element Approach using the Discrete Vortex Model. The method attempts to represent the complex unsteady flow field with separating shear layers in a realistic fashion consistent with the available computational tools. Important steps in the numerical analysis of this challenging problem are discussed at some length in Chapter V and a performance evaluation algorithm established. Of considerable importance is the effect of computational parameters such as number of elements representing the rotor blade, time-step size, location of the nascent vortices, etc., on the accuracy of results and the associated cost. Results obtained using the Discrete Vortex Model are presented and discussed in Chapter VI, for both stationary as well as rotating Savonius configurations. A detailed parametric study provides fundamental information concerning the starting and dynamic torque time histories, power coefficient, evolution of the wake, Strouhal number, etc. A comparison with the flow visualization and wind tunnel test data (Chapter II) shows remarkable correlation suggesting considerable promise for the approach. The thesis ends with concluding remarks and a few suggestions concerning possible future research in the area.
Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate

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Zhu, Wenjin. "Maintenance of monitored systems with multiple deterioration mechanisms in dynamic environments : application to wind turbines." Thesis, Troyes, 2014. http://www.theses.fr/2014TROY0005/document.

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Les travaux présentés contribuent à la modélisation stochastique de la maintenance de systèmes mono- ou multi-composants à détériorations et à modes de défaillances multiples en environnement dynamique. Dans ce cadre, les contributions portent d'une part sur la modélisation des processus de défaillance, et d'autre part sur la proposition de structures de décision de maintenance intégrant les différents types d'information de surveillance en ligne disponible sur le système (état de détérioration mesuré ou reconstruit, état de l'environnement, ...) et le développement des modèles mathématiques d'évaluation associés. Les modèles de détérioration et de défaillances proposés pour les systèmes mono-composants permettent de rendre compte de sources de détérioration multiples (chocs et détérioration graduelle) et d'intégrer les effets de l'environnement sur la dégradation. Pour les systèmes multi-composants, on insiste sur les risques concurrents, indépendants ou dépendants et sur l'intégration de l'environnement. Les modèles de maintenance développés sont adaptés aux modèles de détérioration proposés et permettent de prendre en compte la contribution de chaque source de détérioration dans la décision de maintenance, ou d'intégrer de l'information de surveillance indirecte dans la décision, ou encore de combiner plusieurs types d'actions de maintenance. Dans chaque cas, on montre comment les modèles développés répondent aux problématiques de la maintenance de turbines et de parcs éoliens
The thesis contributes to stochastic maintenance modeling of single or multi-components deteriorating systems with several failure modes evolving in a dynamic environment. In one hand, the failure process modeling is addressed and in the other hand, the thesis proposes maintenance decision rules taking into account available on-line monitoring information (system state, deterioration level, environmental conditions …) and develops mathematical models to measure the performances of the latter decision rules.In the framework of single component systems, the proposed deterioration and failure models take into account several deterioration causes (chocks and wear) and also the impact of environmental conditions on the deterioration. For multi-components systems, the competing risk models are considered and the dependencies and the impact of the environmental conditions are also studied. The proposed maintenance models are suitable for deterioration models and permit to consider different deterioration causes and to analyze the impact of the monitoring on the performances of the maintenance policies. For each case, the interest and applicability of models are analyzed through the example of wind turbine and wind turbine farm maintenance

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Hamilton, Nicholas Michael. "Wake Character in the Wind Turbine Array: (Dis-)Organization, Spatial and Dynamic Evolution and Low-dimensional Modeling." PDXScholar, 2016. http://pdxscholar.library.pdx.edu/open_access_etds/3084.

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To maximize the effectiveness of the rapidly increasing capacity of installed wind energy resources, new models must be developed that are capable of more nuanced control of each wind turbine so that each device is more responsive to inflow events. Models used to plan wind turbine arrays and control behavior of devices within the farm currently make questionable estimates of the incoming atmospheric flow and update turbine configurations infrequently. As a result, wind turbines often operate at diminished capacities, especially in arrays where wind turbine wakes interact and inflow conditions are far from ideal. New turbine control and wake prediction models must be developed to tune individual devices and make accurate power predictions. To that end, wind tunnel experiments are conducted detailing the turbulent flow in the wake of a wind turbine in a model-scale array. The proper orthogonal decomposition (POD) is applied to characterize the spatial evolution of structures in the wake. Mode bases from distinct downstream locations are reconciled through a secondary decomposition, called double proper orthogonal decomposition (DPOD), indicating that modes of common rank in the wake share an ordered set of sub-modal projections whose organization delineates underlying wake structures and spatial evolution. The doubly truncated basis of sub-modal structures represents a reduction to 0.015% of the total degrees of freedom of the wind turbine wake. Low-order representations of the Reynolds stress tensor are made using only the most dominant DPOD modes, corrected to account for energy excluded from the truncated basis with a tensor of constant coefficients defined to rescale the low-order representation of the stresses to match the original statistics. Data from the wind turbine wake are contrasted against simulation data from a fully-developed channel flow, illuminating a range of anisotropic states of turbulence. Complexity of flow descriptions resulting from truncated POD bases is suppressed in severe basis truncations, exaggerating anisotropy of the modeled flow and, in extreme cases, can lead to the loss of three dimensionality. Constant corrections to the low-order descriptions of the Reynolds stress tensor reduce the root-mean-square error between low-order descriptions of the flow and the full statistics as much as 40% and, in some cases, reintroduce three-dimensionality to severe truncations of POD bases. Low-dimensional models are constructed by coupling the evolution of the dynamic mode coefficients through their respective time derivatives and successfully account for non-linear mode interaction. Deviation between time derivatives of mode coefficients and their least-squares fit is amplified in numerical integration of the system, leading to unstable long-time solutions. Periodic recalibration of the dynamical system is undertaken by limiting the integration time and using a virtual sensor upstream of the wind turbine actuator disk in to read the effective inflow velocity. A series of open-loop transfer functions are designed to inform the low-order dynamical system of the flow incident to the wind turbine rotor. Validation data shows that the model tuned to the inflow reproduces dynamic mode coefficients with little to no error given a sufficiently small interval between instances of recalibration. The reduced-order model makes accurate predictions of the wake when informed of turbulent inflow events. The modeling scheme represents a viable path for continuous time feedback and control that may be used to selectively tune a wind turbine in the effort to maximize power output of large wind farms.

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Melius, Matthew Scott. "Identification of Markov Processes within a Wind Turbine Array Boundary Layer." PDXScholar, 2013. https://pdxscholar.library.pdx.edu/open_access_etds/1422.

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The Markovianity within a wind turbine array boundary layer is explored for data taken in a wind tunnel containing a model wind turbine array. A stochastic analysis of the data is carried out using Markov chain theory. The data were obtained via hot-wire anemometry thus providing point velocity statistics. The theory of Markovian processes is applied to obtain a statistical description of longitudinal velocity increments inside the turbine wake using conditional probability density functions. It is found that two and three point conditional probability density functions are similar for scale differences larger than the Taylor micro-scale. This result is quantified by use of the Wilcoxon rank-sum test which verifies that this relationship holds independent of initial scale selection outside of the near-wake region behind a wind turbine. Furthermore, at the locations which demonstrate Markovian properties there is a well defined inertial sub-range which follows Kolmogorv's -5/3 scaling behavior. Results indicate an existence of Markovian properties at scales on the order of the Taylor micro-scale, λ for most locations in the wake. The exception being directly behind the tips of the rotor and the hub where the complex turbulent interactions characteristic of the near-wake demonstrate influence upon the Markov process. The presence of a Markov process in the remaining locations leads to characterization of the multi-point statistics of the wind turbine wakes using the most recent states of the flow.

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Hamilton, Nicholas Michael. "Anisotropy of the Reynolds Stress Tensor in the Wakes of Counter-Rotating Wind Turbine Arrays." PDXScholar, 2014. https://pdxscholar.library.pdx.edu/open_access_etds/1848.

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A wind turbine array was constructed in the wind tunnel at Portland State University in a standard Cartesian arrangement. Configurations of the turbine array were tested with rotor blades set to rotate in either a clockwise or counter-clockwise sense. Measurements of velocity were made with stereo particle-image velocimetry. Mean statistics of velocities and Reynolds stresses clearly show the effect of direction of rotation of rotor blades for both entrance and exit row turbines. Rotational sense of the turbine blades is visible in the mean spanwise velocity W and the Reynolds shear stress -[macron over vw]. The normalized anisotropy tensor was decomposed yielding invariants [lowercase eta] and [lowercase xi], which are plotted onto the Lumley triangle. Invariants of the normalized Reynolds stress anisotropy tensor indicate that distinct characters of turbulence exist in regions of the wake following the nacelle and the rotor blade tips. Eigendecomposition of the tensor yields principle components and corresponding coordinate system transformations. Characteristic spheroids are composed with the eigenvalues from the decomposition yielding shapes predicted by the Lumley triangle. Rotation of the coordinate system defined by the eigenvectors demonstrates streamwise trends, especially trailing the top rotor tip and below the hub of the rotors. Direction of rotation of rotor blades is evidenced in the orientation of characteristic spheroids according to principle axes. The characteristic spheroids of the anisotropy tensor and their relate alignments varies between cases clearly seen in the inflows to exit row turbines. There the normalized Reynolds stress anisotropy tensor shows cumulative effects of the rotational sense of upstream turbines. Comparison between the invariants of the Reynolds stress anisotropy tensor and terms from the mean mechanical energy equation indicate a correlation between the degree of anisotropy and the regions of the wind turbine wakes where turbulence kinetic energy is produced. The flux of kinetic energy into the momentum-deficit area of the wake from above the canopy is associated with prolate characteristic spheroids. Flux upward into the wake from below the rotor area is associate with oblate characteristic spheroids. Turbulence in the region of the flow directly following the nacelle of the wind turbines demonstrates more isotropy compared to the regions following the rotor blades. The power and power coefficients for wind turbines indicate that flow structures on the order of magnitude of the spanwise turbine spacing that increase turbine efficiency depending on particular array configuration.

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Pang, Zhongyuan. "Dynamic models for wind turbines." Thesis, Pang, Zhongyuan (2014) Dynamic models for wind turbines. Other thesis, Murdoch University, 2014. https://researchrepository.murdoch.edu.au/id/eprint/23213/.

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With the increase of wind power capacity, wind energy is now becoming an essential part of energy production system. High wind power penetration may increase the instability of grid due to the characteristic of wind. Fortunately, with the development of power electronics, it is possible to provide a relatively stable energy production by applying power electronics to wind turbine. Due to the complexity of wind turbine, a generic dynamic model of wind turbine can be helpful. The objective of the work is to develop a general wind turbine models that can be used for investigations. The report had tracked the theory of wind turbine and its development, three different kinds of wind turbine are included, which are fixed speed wind turbine, variable slip wind turbine and doubly-fed induction generator wind turbine. Fundamental working theory and a model built by Matlab was provided for each of technology. Assessment for the models was done to prove that it has the ability to reflect the characteristic of wind turbine. Despite from that, the models were done in three phase, so it has the ability to do with load flow analysis or grid stability.

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8

Krysiński, Tomasz. "Mathematical modelling and shape optimisation of vertical axis wind turbines blades." Rozprawa doktorska, ISBN 978-83-61506-47-8, 2018. https://repolis.bg.polsl.pl/dlibra/docmetadata?showContent=true&id=53466.

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Krysiński, Tomasz. "Mathematical modelling and shape optimisation of vertical axis wind turbines blades." Rozprawa doktorska, ISBN 978-83-61506-47-8, 2018. https://delibra.bg.polsl.pl/dlibra/docmetadata?showContent=true&id=53466.

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Benjanirat, Sarun. "Computational studies of the horizontal axis wind turbines in high wind speed condition using advanced turbulence models." Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-08222006-145334/.

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Thesis (Ph. D.)--Aerospace Engineering, Georgia Institute of Technology, 2007.
Samual V. Shelton, Committee Member ; P.K. Yeung, Committee Member ; Lakshmi N. Sankar, Committee Chair ; Stephen Ruffin, Committee Member ; Marilyn Smith, Committee Member.

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Schmidt, Michael Frank. "Economic optimization of wind turbine design." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19740.

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Arnold, Robert John. "Mathematical modelling of wind effects on closed lakes /." Title page, contents and summary only, 1985. http://web4.library.adelaide.edu.au/theses/09PH/09pha758.pdf.

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夏激揚 and Jiyang Xia. "Numerical study on wind field and air pollutant dispersion in urban street canopies." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2000. http://hub.hku.hk/bib/B31242509.

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Duhaut, Thomas H. A. "Wind-driven circulation : impact of a surface velocity dependent wind stress." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=101117.

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The use of an ocean surface velocity dependent wind stress is examined in the context of a 3-layer double-gyre quasigeostrophic wind-driven ocean circulation model. The new wind stress formulation results in a large reduction of the power input by the wind into the oceanic circulation. This wind stress is proportional to a quadratic function of Ua--u o, where Ua is the wind at 10m above the ocean surface and uo is the ocean surface current. Because the winds are typically faster than the ocean currents, the impact of the ocean surface velocity on the wind stress itself is relatively small. However, the power input is found to be greatly reduced with the new formulation. This is shown by simple scaling argument and numerical simulations in a square basin. Our results suggest that the wind power input may be as much as 35% smaller than is typically assumed.
The ocean current signature is clearly visible in the scatterometer-derived wind stress fields. We argue that because the actual ocean velocity differs from the modeled ocean velocities, care must be taken in directly applying scatterometer-derived wind stress products to the ocean circulation models. This is not to say that the scatterometer-derived wind stress is not useful. Clearly the great spatial and temporal coverage make these data sets invaluable. Our point is that it is better to separate the atmospheric and oceanic contribution to the stresses.
Finally, the new wind stress decreases the sensitivity of the solution to the (poorly known) bottom friction coefficient. The dependence of the circulation strength on different values of bottom friction is examined under the standard and the new wind stress forcing for two topographic configurations. A flat bottom and a meridional ridge case are studied. In the flat bottom case, the new wind stress leads to a significant reduction of the sensitivity to the bottom friction parameter, implying that inertial runaway occurs for smaller values of bottom friction coefficient. The ridge case also gives similar results. In the case of the ridge and the new wind stress formulation, no real inertial runaway regime has been found over the range of parameters explored.

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Radulovic, Luka. "Influence of advanced load simulation models on fatigue design of jackets for offshore wind turbines." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amslaurea.unibo.it/6369/.

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Constant developments in the field of offshore wind energy have increased the range of water depths at which wind farms are planned to be installed. Therefore, in addition to monopile support structures suitable in shallow waters (up to 30 m), different types of support structures, able to withstand severe sea conditions at the greater water depths, have been developed. For water depths above 30 m, the jacket is one of the preferred support types. Jacket represents a lightweight support structure, which, in combination with complex nature of environmental loads, is prone to highly dynamic behavior. As a consequence, high stresses with great variability in time can be observed in all structural members. The highest concentration of stresses occurs in joints due to their nature (structural discontinuities) and due to the existence of notches along the welds present in the joints. This makes them the weakest elements of the jacket in terms of fatigue. In the numerical modeling of jackets for offshore wind turbines, a reduction of local stresses at the chord-brace joints, and consequently an optimization of the model, can be achieved by implementing joint flexibility in the chord-brace joints. Therefore, in this work, the influence of joint flexibility on the fatigue damage in chord-brace joints of a numerical jacket model, subjected to advanced load simulations, is studied.

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Luo, Zhiwen, and 罗志文. "City ventilation by slope wind." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B46089962.

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Kiss, Andrew Elek. "Dynamics of laboratory models of the wind-driven ocean circulation." View thesis entry in Australian Digital Theses Program, 2000. http://thesis.anu.edu.au/public/adt-ANU20011018.115707/index.html.

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Wilson, Amanda C. "Equivalent initial flaw size model development for turbine blades using in-service data." Thesis, Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/20006.

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Crawford, C. A. "Advanced engineering models for wind turbines with application to the design of a coning rotor concept." Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.598134.

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The primary theoretical contribution of this work is an enhanced Blade Element Momentum (BEM) method. Utilizing vortex theory to model induction, computationally efficient corrections are derived that are key in more accurately predicting performance for coned rotors. The theory is extended to include wake expansion, dynamic inflow, and yawed conditions, as well as considering centrifugal and radial-flow induced stall-delay. The theory is favourably validated against Computational Fluid Dynamics (CFD) and experimental results for both real and idealized rotors. BLADED^TM was to be modified with the enhanced BEM method for dynamic analyses. To support these analyses, a beam sectional model and Finite Element Method (FEM) approach to the generalized centrifugally stiffened beam problem were implemented. Ultimately, the linear structural theory in current codes precluded accurate predictions at large flap angles. In lieu of a fully non-linear flexible-body simulation, a rigid-body dynamic model of the system was developed. The coupled aerodynamic and structural models were then used to analyse steady-state and dynamic operation, including optimal control schedules. Parametric optimization studies were used to examine the interplay between design variables for the coning rotor, relative to a reference conventional machine. Increased blade length, shape and airfoil choice were found to be tightly coupled, yielding energy gains of 10-30% over conventional rotors. Airfoil choice and control mechanism were found critical to limiting torque and thrust. The fundamental non-linear open-loop dynamics were also examined, including flap and edgewise damping behaviour. Low-Frequency Noise (LFN) was computed with a properly implemented physics-based model, to quantify sensitivity to design and operational parameters. The current work is a preliminary, but critical step, in proving the worth of the coning rotor. Controlled design and an accurate flexible-body code will be required for full load-set simulations, to affect detailed component design and costing. Ultimately, prototype testing will be needed to validate the complicated stalling behaviour of the coning rotor.

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HEKİM, MEHMET ÇAĞRI. "WAKE EFFECT IMPACTS ON THE ENERGY PRODUCTION OF THREE WIND TURBINES IN CLOSE CONFIGURATION." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-256007.

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With the rapid expansion of offshore wind power capacity in the world in the last decade, innovative offshore solutions are designed in order to meet the upcoming power capacity installations. As in all other energy sectors, offshore wind power has certain conditions that have to be met to increase the efficacy of the outcome.In this thesis, wake effect impact on the production results of Hexicon AB’s innovative floating and rotating offshore wind power platform project with 3 turbines located in the southern part of Sweden are analyzed through the application of “Analytical wake models” and the “Actuator Disc method”, with the help of WindSim.The results of Analytical models and Actuator Disc method were found to be independent of one another. Even though analytical wake models did not find any wake effect impact among the turbines, the results can be considered as logical. However, the Actuator Disc method created unexpected results which might stem from the WindSim – AD combination. It is therefore recommended to further explore these scenarios with other (more) advanced simulation tools.

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Hang, Jian, and 杭建. "Wind conditions and urban ventilation in idealized city models." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B42841471.

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Cheng, Wai-chi, and 鄭偉智. "Wind and pollutant removal of urban street canyons under different thermal stratification by RANS and LES models." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B46289653.

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Li, Xianxiang, and 李顯祥. "Large-eddy simulation of wind flow and air pollutant transport inside urban street canyons of different aspect ratios." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B40687326.

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Kwon, Sun Hong. "Directional growth of wind generated waves." Diss., Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/49816.

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Ochs, David S. "Design of detailed models for use in fast aeroelastic simulations of permanent-magnet direct-drive wind turbines." Thesis, Kansas State University, 2012. http://hdl.handle.net/2097/15042.

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Master of Science
Department of Electrical and Computer Engineering
Ruth Douglas Miller
This thesis presents the design of two models for permanent-magnet direct-drive wind turbines. The models are of a 10 kW and a 5 MW wind turbine, which are representative of residential scale and commercial scale turbines respectively. The models include aerodynamic and mechanical simulations through the FAST software, as well as concurrent electrical simulations through the SimPowerSystems toolbox for MATLAB/Simulink. The aim is to provide wind turbine designers and researchers with a comprehensive simulation tool that they can use to design and test many different aspects of a wind turbine. The particular novelty of these models is their high level of detail in electromechanical simulations. For each model, a generator speed controller was designed in a reference frame attached to the generator’s rotor, and was executed with a 3-phase active rectifier using space-vector pulse-width modulation. Also for each model, active and reactive power controllers were designed in a reference frame synchronous with the grid, and were executed with a 3-phase inverter using space-vector pulse-width modulation. Additionally, a blade pitch controller was designed for the 5 MW model. Validation of the models was carried out in the MATLAB/Simulink environment with satisfactory results.

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Jung, Kyung Tae. "On three-dimensional hydrodynamic numerical modelling of wind induced flows in stably stratified waters : a Galerkin-finite difference approach." Title page, contents and summary only, 1989. http://web4.library.adelaide.edu.au/theses/09PH/09phj95.pdf.

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Allen, Carrie E. "A computational and experimental examination of turbine cooling flows." Thesis, University of Oxford, 1996. http://ora.ox.ac.uk/objects/uuid:408752e3-cc6d-48e5-8bb7-6099162e3ff6.

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Film cooling by means of holes is an essential cooling technique in modern gas turbine engines. This cooling technique is employed over endwalls, as well as on the surface of blades. Thus, there is a need for film cooling predictions in a three-dimensional setting. Currently only boundary layer codes are available for design purposes and they are difficult to apply to the three-dimensional case with secondary flows. Present advanced computation prediction methods are capable of solving the complete flow field in three dimensions with coolant flow. However, the spatial resolution that these methods require eliminate them as suitable options for design tools This study introduces a simpler description of the film cooling process which may be implemented in a code for design purposes. The parameters of turbulence enhancement, turbulence decay, and the coolant distribution at injection were optimized using existing experimental data. Finally, the code was employed in a three-dimensional setting with film cooling present. An experimental study of the flow through cooling holes was also undertaken. Two unique geometries were later developed where a row of cooling holes exited into a vortex region where the flow was mixed before being injected from a slot. The cooling benefits of these geometries is apparent.

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李永智 and Wing-chi Steven Lee. "Analytical study of wind flow and pollutant dispersion past hills." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2000. http://hub.hku.hk/bib/B31224672.

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Relation, Heather L. "Application of a modified k-[epsilon] turbulence model to gas turbine combustor geometries." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-10312009-020353/.

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So, Shuk-pan Ellen, and 蘇淑彬. "Large eddy simulations of wind flow and pollution dispersion in an urban street canyon." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2003. http://hub.hku.hk/bib/B29332710.

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Hagen, Torbjørn Ruud. "Numerical Simulations of Flow Past a Truss Tower with an Evaluation of Tower Shadow Models for Wind Turbines." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-13726.

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The performance of steady-state tower shadow models for a wind turbine truss tower have been evaluated. The Reynolds-Averaged-Navier-Stokes (RANS) approach, in conjunction with the $k-omega$ Shear-Stress-Transport (SST) model, was used to simulate transient flows past cross sections of a truss tower. The objective was to compare numerical results with Powles', Blevins' and Schlichting's tower shadow models and evaluate their performance on a multimember structure. Parameters for each model have been estimated. It will be shown that the RANS model was able to reproduce realistic results when used in transient simulations on high Reynolds number flows (supercritical regime). The importance of considering unsteady motion when calculating the turbulence intensity, using RANS with transient simulations, will be explained. The multimember extension used for the tower shadow models reproduces the mean velocity profiles quite well, and by using a suitable estimation method, global parameters were found for all models. Additionally, turbulent inflow has been implemented with a user-defined function in Fluent. The results have been evaluated, and show that such such sophisticated inflow modeling is not necessary to predict realistic mean velocity profiles.

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Avila-Pozos, Orlando. "Mathematical models of layered structures with an imperfect interface and delamination cracks." Thesis, University of Bath, 1999. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.311186.

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黃潤棠 and Yun-tong Anton Wong. "Computational study of wind flow and pollution dispersion in an urban street canyon of various geometries." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2002. http://hub.hku.hk/bib/B31226905.

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Thornhill, Kenneth L. II. "An investigation of the environment surrounding supercell thunderstorms using wind profiler data." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/26958.

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Nelson, Edward L. "Temperature, pressure, and infrared image survey of an axisymmetric heated exhaust plume." Diss., This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-06062008-171052/.

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Ben, Hassine Seif. "Multipath and receiver models for assessing the VOR bearing error : application to wind farms." Thesis, Toulouse 3, 2020. http://www.theses.fr/2020TOU30047.

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L'implémentation des éoliennes à proximité des systèmes VOR (VHF Omnidirectional Range) est une préoccupation importante pour l'aviation civile. Les éoliennes constituent une source de multitrajets qui peuvent produire des erreurs sur l'information d'azimut estimée par le récepteur d'avion. Dans la littérature, l'erreur VOR est calculée à partir de paramètres multitrajets en utilisant l'expression analytique proposée par Odunaiya et Quinet. Dans cette thèse de doctorat, nous avons développé un modèle d'un récepteur IQ numérique qui peut reproduire la réponse d'un récepteur VOR lorsque les multitrajets varient dans le temps tout au long d'une trajectoire réaliste d'avion. Le Chapitre 1 présente les principes de base des systèmes : VOR conventionnel (VORC) et VOR Doppler (VORD). Le phénomène de multitrajets générés par les éoliennes à proximité des stations VOR est détaillé en présentant ses paramètres et certaines méthodes de modélisation associées qui existent dans la littérature. Un aperçu des récepteurs VOR est présenté en décrivant la structure classique d'un récepteur VOR et les étapes du traitement du signal appliquées afin d'extraire l'information d'azimut. Les expressions de l'erreur VOR proposées par Odunaiya et Quinet pour les systèmes VORC et VORD sont données et illustrées. Dans le Chapitre 2, nous présentons notre modèle de récepteur IQ numérique. Un générateur de séries temporelles au long d'une trajectoire réaliste d'avion est présenté. Un critère échantillonnage est également proposé pour être sûr de capturer toutes les variations de multitrajets dans l'espace. Le modèle de récepteur IQ numérique est détaillé en décrivant ses composantes. Afin d'analyser l'effet et dynamique de multitrajets sur le récepteur VOR, un test d'illustration est donné en comparant la réponse du modèle avec l'expression d'Odunaiya. Dans le Chapitre 3, le comportement de notre modèle de récepteur IQ numérique est analysé en le comparant avec un récepteur de calibration (R&S EVS300) à l'aide de deux mesures de laboratoire. La première mesure est effectuée dans la bande des fréquences VHF en traitant un multitrajet canonique. La seconde mesure est effectuée en utilisant des signaux en bande de base IQ générées à partir d'une simulation d'un scénario complexe. Les résultats des mesures montrent un bon accord entre les récepteurs. Une analyse critique de récepteur VOR est présentée dans le Chapitre 4. Pour le VORC, nous présentons une méthode permettant de déterminer le domaine de validité de l'expression statique d'Odunaiya afin de calculer l'erreur VOR. Pour le VORD, nous montrons que l'erreur VOR est sensible au type de démodulateur FM en développant et en validant une expression alternative de l'erreur Doppler analytique qui est cohérente avec notre démodulateur FM. Enfin, nous évaluons l'analyse de Bredemeyer qui indique que l'effet et des multitrajets sur le signal de référence doit être pris en compte dans le calcul de l'erreur VORD. Dans le Chapitre 5, nous proposons un modèle statistique d'erreur VOR dont les seuls paramètres sont les positions de l'avion et de l'éolienne et les autres paramètres suivent des distributions statistiques. Ce modèle permet de réduire le temps de simulation électromagnétique. Tout d'abord, nous déterminons les distributions statistiques associées aux paramètres multitrajets. Ensuite, la distribution statistique associée à l'erreur VOR est déduite. Enfin, nous effectuons des simulations de Monte Carlo pour évaluer les paramètres des distributions statistiques
The implementation of wind turbines close to VHF Omnidirectional Range (VOR) systems is an important concern for civil aviation. The wind turbines constitute a source of multipath that can yield bearing errors in the azimuth estimated by aircraft receivers. In the literature, the bearing error is computed from the multipath characteristics by means of the analytic expression proposed by Odunaiya and Quinet. In this PhD thesis, we have developed a digital IQ receiver model which can reproduce the response of a VOR receiver when the multipath change in time along a realistic aircraft trajectory. In Chapter 1, the basic principle of the Conventional VOR (CVOR) and Doppler VOR (DVOR) is pre-sented. The multipath phenomenon generated by the wind turbines in the vicinity of VOR stations is detailed by presenting its parameters and some associated modeling methods that exist in the literature. An overview of the VOR receivers is presented by describing the standard structure of a VOR receiver and the signal processing steps to extract the azimuth information. The analytical expressions proposed by Odunaiya and Quinet for the CVOR and DVOR systems are given and illustrated. In Chapter 2, we present our digital IQ receiver model. A time series generator along a realistic aircraft trajectory is presented. A sampling criterion is also proposed to be sure to capture all the multipath variations in space. The digital IQ receiver model is detailed by describing its components. In order to analyze the effect of multipath dynamics on the VOR receiver, an illustration test is given by comparing the receiver model response with the Odunaiya expression. In Chapter 3, the behavior of our digital IQ receiver model is analyzed by comparing with a calibration receiver (R&S EVS300) from two laboratory measurements. The first one is performed in the VHF frequency band for one canonical multipath. The second one is performed using baseband IQ signals in a complex scenario. The measurements results are shown a good agreement between receivers. A CVOR and DVOR analysis are given in Chapter 4. For CVOR, we present a method to determine the validity domain of the static Odunaiya expression for computing the bearing error. For DVOR, we show that the bearing error is sensitive to the type of FM demodulator by developing and validating an alternative expression of the analytic Doppler error which is consistent with our FM demodulator. Finally, we evaluate the analysis of Bredemeyer which indicates that the effect of multipath on the reference signal must be considered in the DVOR error computation. In Chapter 5, we propose a statistical model for the bearing error with which the only parameters are the aircraft and wind turbine positions and the other parameters follow statistical distributions. This model allows to reduce the electromagnetic simulation time. Firstly, we determine the statistical distributions associated with the multipath parameters. Secondly, the statistical distribution associated with the bearing error is deduced. Finally, we perform Monte Carlo simulations to assess the parameters of the statistical distributions

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Barchyn, Thomas Edward, and University of Lethbridge Faculty of Arts and Science. "Field-based aeolian sediment transport threshold measurement : sensors, calculation methods, and standards as a strategy for improving inter-study comparison." Thesis, Lethbridge, Alta. : University of Lethbridge, Dept. of Geography, 2010, 2010. http://hdl.handle.net/10133/2616.

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Aeolian sediment transport threshold is commonly defined as the minimum wind speed (or shear stress) necessary for wind-driven sediment transport. Threshold is a core parameter in most models of aeolian transport. Recent advances in methodology for field-based measurement of threshold show promise for improving parameterizations; however, investigators have varied in choice of method and sensor. The impacts of modifying measurement system configuration are unknown. To address this, two field tests were performed: (i) comparison of four piezoelectric sediment transport sensors, and (ii) comparison of four calculation methods. Data from both comparisons suggest that threshold measurements are non-negligibly modified by measurement system configuration and are incomparable. A poor understanding of natural sediment transport dynamics suggests that development of calibration methods could be difficult. Development of technical standards was explored to improve commensurability of measurements. Standards could assist future researchers with data syntheses and integration.
xi, 108 leaves : ill. ; 29 cm

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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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Berg, Allison M. "The feasibility of sodar wind profile measurements from an oceanographic buoy." Thesis, (37 MB), 2006. http://handle.dtic.mil/100.2/ADA471871.

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Thesis (M.S.)--Massachusetts Institute of Technology at Woods Hole Oceanographic Institution, 2006.
"September 2006." Description based on title screen as viewed on June 8, 2010. DTIC Descriptor(s): Doppler Radar, Wind Velocity, Sound Ranging, Doppler Sonar, Buoys, Measurement, Motion, Oceanographic Equipment, Theses DTIC Identifier(s): Doppler Sodar, Sodar (Sound Detection and Ranging), ASIS Includes bibliographical references (leaf 75). Also available in print.

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40

Pannala, Sreekanth. "On large eddy simulations of reacting two-phase flows." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/11978.

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41

Guimarães, da Silva Jôse Lorena. "Computational sound propagation models: An analysis of the models Nord2000, CONCAWE, and ISO 9613-2 for sound propagation from a wind farm." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-331752.

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The recent goals from some countries to become renewable energy based and reduce carbon dioxide emissions have caused the wind industry to grow. Together, the size of the wind farms and the noise emission have grown, while the noise emission regulations have to be fulfilled. Numerical simulations based on engineering approaches are in many cases a fast alternative that may supplement actual sound measurements at the site on question. However, the sound propagation models have many assumptions and estimations, as different variants can affect the resulting sound propagation. The accuracy of the sound propagation models Nord2000, CONCAWE, and ISO 9613-2 are investigated in this research by comparing the predicted to the measured sound pressure levels from a wind farm in northern Sweden. Different parameters were investigated in each model, as wind speed and direction, roughness length, ground class, temperature gradient, and receiver height. The computational calculations were run on SoundPLAN software for a single point, the nearby dwelling. For the different parameters investigated, the settings were defined and inputted in the software, and the calculations were run. The equivalent sound pressure level results from the computational models were compared to the equivalent sound pressure level of the sound measurements filtered from background noise. The results indicate that the model ISO 9613-2 did not perform well for the specific site conditions at the wind farm. On the other hand, the CONCAWE and Nord2000 showed high accuracy, for downwind conditions at 8 m/s. For upwind conditions at 8 m/s, Nord2000 is more accurate, as the refraction of the sound rays are better calculated on this model. For the variants investigated on the Nord2000 model, the results that better approximate to the sound levels of the sound measurements are the roughness length 0.3, ground class D, and temperature gradient 0.05 K/m. Thus, these settings would be recommended for calculations with Nord2000 for noise assessment in a permit process.

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Shan, Martin [Verfasser]. "Load Reducing Control for Wind Turbines: Load Estimation and Higher Level Controller Tuning based on Disturbance Spectra and Linear Models / Martin Shan." Kassel : Universitätsbibliothek Kassel, 2017. http://d-nb.info/1154972496/34.

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Cheung, Ching, and 張靜. "Effect of heat flux on wind flow and pollutant dispersion in an urban street canyon." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B37742498.

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Alves, Jose Henrique Gomes de Mattos Mathematics UNSW. "A Saturation-Dependent Dissipation Source Function for Wind-Wave Modelling Applications." Awarded by:University of New South Wales. Mathematics, 2000. http://handle.unsw.edu.au/1959.4/17786.

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This study reports on a new formulation of the spectral dissipation source term Sds for wind-wave modelling applications. This new form of Sds features a nonlinear dependence on the local wave spectrum, expressed in terms of the azimuthally integrated saturation parameter B(k)=k^4 F(k). The basic form of this saturation-dependent Sds is based on a new framework for the onset of deep-water wave breaking due to the nonlinear modulation of wave groups. The new form of Sds is succesfully validated through numerical experiments that include exact nonlinear computations of fetch-limited wind-wave evolution and hindcasts of two-dimensional wave fields made with an operational wind-wave model. The newly-proposed form of Sds generates integral spectral parameters that agree more closely with observations when compared to other dissipation source terms used in state-of-the-art wind-wave models. It also provides more flexibility in controlling properties of the wave spectrum within the high wavenumber range. Tests using a variety of wind speeds, three commonly-used wind input source functions and two alternative full-development evolution limits further demonstrate the robustness and flexibility of the new saturation-dependent dissipation source term. Finally, improved wave hindcasts obtained with an implementation of the new form of Sds in a version of the WAM model demonstrate its potential usefulness in operational wind-wave forecasting applications.

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Barnaud, Félix. "Influence of advanced unsteady aerodynamic models on the aeroelastic response of an offshore wind turbine." Thesis, Normandie, 2019. http://www.theses.fr/2019NORMIR31.

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Les éoliennes offshore modernes ont atteint ces dernières années de très grandes dimensions, qui ne cessent d’augmenter en vue de diminuer les coûts de production de l’électricité. Des designs innovants sont alors nécessaires afin d’améliorer les performances aérodynamiques et de réduire les charges structurelles. Les outils de l’état de l’art tels que la théorie de l’élément de pale couplée à la méthode de la quantité de mouvement (BEMT en anglais), utilisés pour la prédiction des charges et performances des rotors, ont été conçus pour des rotors de plus faibles dimensions et dans des conditions standards d’utilisation. Des conditions particulières comme les cas de désalignement du rotor par rapport à l’axe du vent sont a priori hors du domaine de validité des outils de l'état de l'art. Le but de cette thèse est d'étudier des modèles aérodynamiques plus poussés et de les comparer avec les outils de l'état de l'art sur des cas spécifiques. Les écoulements instationnaires sont particulièrement intéressants puisque difficiles à simuler avec les méthodes standards. Ainsi, un code de méthode des panneaux prenant en compte les phénomènes visqueux tels que le décrochage dynamique est comparé à un code BEMT dans des conditions de vent réalistes et avec un fort désalignement du rotor. Les calculs sont réalisés dans le cadre d'un couplage aéro-servo-élastique de manière à être le plus représentatif possible des calculs de chargement effectués dans l'industrie et nécessaires pour la certification des machines. L'impact du modèle de décrochage dynamique est étudié avec les deux méthodes, pour des cas de chargement extrêmes et en fatigue avec désalignement du rotor. Des différences ont été observées entre les deux méthodes et avec plusieurs paramétrisations du modèle de décrochage dynamique. De plus, la prise en compte du couplage servo-élastique modifie les observations faites sur les comparaisons aérodynamiques. De plus, les angles d'attaque observés sur les pales en cas de fort désalignement sont très élevés. L'écoulement autour de profils dans ces conditions est dominé par des effets visqueux non capturés par les méthodes des panneaux ou de BEMT mais modélisés via des modèles semi-empiriques. Des modèles alternatifs doivent donc être utilisés pour mieux prédire de tels phénomènes. Dans la seconde partie de cette thèse l'écoulement autour de profils aérodynamiques d'éoliennes, plus épais que dans l'aéronautique, est étudié à l'aide de Simulation aux Grandes Échelles avec loi de paroi. Plusieurs cas d'écoulement attachés et détachés sont simulés, pour des profils fixes et oscillants. De très grands angles d'attaque sont également simulés, jusqu'à 90°, à un nombre de Reynolds réaliste. Dans les cas attachés et très fortement détachés, la Simulation aux Grandes Échelles avec loi de paroi est capable de capturer correctement l'écoulement avec des maillages peu raffinés. Cependant les cas proches du décrochage se sont révélés plus difficiles à obtenir, et nécessitent des maillages très fins même en utilisant des lois de paroi adéquates. Enfin, des cas oscillants avec fréquence réduite élevée sont également étudiés et comparés avec d'autres modèles. La Simulation aux Grandes Échelles est alors particulièrement adaptée et donne des résultats prometteurs
The size of modern offshore wind turbine rotors has reached very large dimensions and keeps increasing in order to reduce the cost of electricity. More challenging designs are thus needed to improve the aerodynamic performances and reduce the structural loads. The state-of-the-art tools such as Blade Element Momentum Theory (BEMT) used to predict the loads and performances of wind turbines have been designed for much smaller rotors in standard operating conditions. Load cases in specific conditions such as yaw misalignment are a priori out of the validity range for such tools. The goal of the thesis is to investigate more advanced aerodynamic models in order to assess the differences in load predictions compared to state-of-the-art tools. In particular, this work focuses on unsteady flows which represent a challenge for engineering tools. For this purpose, a panel method code including viscous effects such as dynamic stall is compared to a BEMT code in realistic wind conditions with large yaw misalignment. The calculations are performed in the framework of aero-servo-elasto coupling in order to be represen¬tative of the load calculations performed in industry following certification standards. The impact of the dynamic stall model is investigated in particular for both BEMT and panel method, for extreme and fatigue loading in cases of yaw misalignment. Differences have been observed between both codes and for several parametrizations of dynamic stall model. In addition, it has been noticed that including the servo-elasto coupling changes a lot the observations regarding aerodynamic loading. Large angles of at¬tack are observed on wind turbine blades in yaw misalignment cases, and the flow around blade sections in such conditions is particularly affected by viscous effects such as dynamic stall or vortex shedding which are not inherently solved by panel methods nor BEMT but modeled with semi-empirical models. Alternative models such as Large Eddy Simulation (LES) that would capture these effects have to be considered. Wall-modeled LES (WMLES) is thus used in the second part of this thesis to investigate the flow around wind turbine dedicated airfoils, much thicker than airfoils used in aeronautics. Several cases are simulated, for attached and detached flows and in steady or oscillating cases. Angles of attack up to 90° are investigated at realistic Reynolds number. It appears that WMLES is able to capture correctly the main flow features in attached conditions and at very high angle of attack with coarse meshes. However, the near stall cases are more challenging to capture even with appropriate wall laws and require very fine meshes to be correctly solved. A comparison is also performed for motions with high reduced frequency and compared to other models, revealing the promising capacities of WMLES in such cases

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46

Kazlova, Ala, and Bettina Ullmann. "When Wind Goes Vertical: : Can a start-up company make use of its born global potential to revolutionize the wind turbine industry?" Thesis, Linnéuniversitetet, Ekonomihögskolan, ELNU, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-6605.

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The 21st century would be a nightmare for Don Quijote: thousands of windmills are installed all over the globe and the number will increase tremendously over the next years. If climate change was an issue in the early 17th century, Don Quijote might have specialized in fighting nuclear or fossil fuel power plants. The change in power production is clearly pronounced, and it inspires the market to respond immediately. Numerous wind turbine manufacturers emerge, developing one technological innovation after another. The trend clearly goes in one direction: horizontal axis wind turbines in all possible variations. However, there are a few companies that do not follow the mainstream – they swim against the current and introduce new concepts, with the potential to set new standards in the industry. Nevertheless, the question whether these companies can establish operations and survive in an industry dominated by large multinational corporations arises. If these companies want to become recognized, they need to compete on an international scale from the outset – they become born globals. This master’s thesis investigates the preconditions under which an innovative start-up company can become born global in the wind turbine industry. For that, distinctive resources and capabilities of such companies, as well as key success factors for the industry are defined. Furthermore, enhancing or restricting parameters lying within company’s environment – in particular, within its networks – are discovered. These findings are based on and supported by the case study of an innovative vertical axis wind turbine manufacturer. In addition, the influence of this company’s university spin-off origin is investigated.

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He, Yanping. "Representations of boundary layer cloudiness and surface wind probability distributions in subtropical marine stratus and stratocumulus regions." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/22585.

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Thesis (Ph. D.)--Earth and Atmospheric Sciences, Georgia Institute of Technology, 2007.
Committee Chair: Dr. Robert E. Dickinson; Committee Member: Dr. Irina Sokolik; Committee Member: Dr. Judth Curry; Committee Member: Dr. Peter Webster; Committee Member: Dr. Rong Fu.

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48

Qiao, Wei. "Integrated control of wind farms, facts devices and the power network using neural networks and adaptive critic designs." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/29716.

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Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Ronald G. Harley; Committee Member: David G. Taylor; Committee Member: Deepakraj M. Divan; Committee Member: Ganesh Kumar Venayagamoorthy; Committee Member: Thomas G. Habetler. Part of the SMARTech Electronic Thesis and Dissertation Collection.

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49

Ko, Joon Soo. "Analysis of the dynamic stability derivatives for high angle of attack aircraft." Diss., Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/52300.

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Modern, high performance aircraft are required to be able to fly and be controlled over a wide variety of flight conditions. In order to predict the aircraft behavior and control requirements over the entire flight regime it is necessary to have a proper aerodynamic model. Flight conditions at high angles of attack lead to separated flows making the aerodynamic model more difficult to obtain. In this research wind tunnel experiments are performed on an F-5 air-craft model at high angles of attack, with small oscillations about the body oriented roll axis. In addition the free stream environment can be configured in one of three ways: l) straight uniform flow, 2) curved flow to simulated a horizontal turn, and 3) rolling flow to simulated a roll motion about the relative Velocity vector.
Ph. D.

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50

Sanz, 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.

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Antarctic Wind Engineering deals with the effects of wind on the built environment. The assessment of wind induced forces, wind resource and wind driven snowdrifts are the main tasks for a wind engineer when participating on the design of an Antarctic building. While conventional Wind Engineering techniques are generally applicable to the Antarctic environment, there are some aspects that require further analysis due to the special characteristics of the Antarctic wind climate and its boundary layer meteorology.

The 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

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