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1
Dahmer, Marc R. Market Patrick S. "Investigating near-surface wind fields as influenced by low-level jet occurrences in Missouri." Diss., Columbia, Mo. : University of Missouri--Columbia, 2009. http://hdl.handle.net/10355/6555.
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The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Title from PDF of title page (University of Missouri--Columbia, viewed on November 13, 2009). Thesis advisor: Dr. Patrick S. Market Includes bibliographical references.
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Marchenko, S. V. "Wind inhomogeneities in low-Z environment : observations." Universität Potsdam, 2007. http://opus.kobv.de/ubp/volltexte/2008/1776/.
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We discuss the results of time-resolved spectroscopy of three presumably single Population I Wolf-Rayet stars in the Small Magellanic Cloud, where the ambient metallicity is $sim 1/5 Z_odot$. We were able to detect and follow numerous small-scale wind-embedded inhomogeneities in all observed stars. The general properties of the moving features, such as their velocity dispersions, emissivities and average accelerations, closely match the corresponding characteristics of small-scale inhomogeneities in the winds of Galactic Wolf-Rayet stars.
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Harvey, Scott A. "Low-speed wind tunnel flow quality determination." Thesis, Monterey, California. Naval Postgraduate School, 2011. http://hdl.handle.net/10945/5584.
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Approved for public release; distribution is unlimited.lected points. Incorporated instrumentation includes pressure transducers attached to a pitot-static tube, wall static pressure taps, and a pressure rake; a hotwire anemometry system, and a linear traverse system. These were integrated with a data acquisition (DAQ) processor with analog to digital conversion and digital I/O boards, and controlled using in-house developed LabVIEW software. Testing showed a maximum axial velocity of 38 m/s, which is 84% of the tunnel?s rated speed. The 2-D flow uniformity was within ±7% by pressure rake, and ±3% with a turbulence intensity ?0.11% at full speed using a CTA, affirming the tunnel?s viability as a demonstration platform. Spectral density plots in the boundary layer exhibit typical behavior of fully developed equilibrium turbulent flow with an intertial sub-range present. Future testing of a flat-plate wake for drag modification is planned.
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Keeli, Anupama. "Low frequency transmission for remote power generating systems." Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41190.
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The goal of this Masters Thesis research is to evaluate alternative transmission systems from remote wind farms to the main grid using low-frequency AC technology. Low frequency means a frequency lower than nominal frequency (60/50Hz). The low-frequency AC network can be connected to the power grid at major substations via cyclo-converters that provide a low-cost interconnection and synchronization with the main grid. Cyclo-converter technology is utilized to minimize costs which result in systems of 20/16.66 Hz (for 60/50Hz systems respectively). Low frequency transmission has the potential to provide an attractive solution in terms of economics and technical merits.
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Alam, Muhammad Mahbubul. "Wind-driven rotodynamic pumps for low-lift applications." Thesis, University of Reading, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359007.
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Prevezer, Tanya. "Wind pressure fluctuations on a low-rise building." Thesis, University of Nottingham, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287236.
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Wang, Shuai. "The low-level wind structure of tropical cyclones." Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/44564.
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The main effects of tropical cyclones include high winds, extensive storm surges, and widespread flooding. These main effects are all closely related to the low-level wind structure, the height of which is about 2 km from the underlying surface. A physically based analytic model (λ model) is presented to describe the low-level wind structure of tropical cyclones in terms of one intensity measure, one size measure, and the storm meridional position. The λ model provides an accurate fit of the near-surface azimuthal wind field simulated with an idealized full-physics numerical model. This numerical model is further applied to investigate the tropical cyclone low-level wind structure evolution during the mature stage with observations. Three basic features at the mature stage are observed: the outward expansion of eyewall, the reduction of intensity and the increase of tangential wind in the outer spiral bands. Model simulations show that the outer circulation expansion is accompanied by the outward migration of diabatic heating at mid-level in the eyewall. The outward movement of eyewall is caused by the opposing angular momentum transports. Consequently, the intensity decays due to the angular momentum conservation and cyclostrophic adjustment, which is captured in a new analytic pressure-wind relationship derived from the λ model. To investigate the relationship between the tropical cyclone damage and low-level wind structure, the λ model is used to reconstruct the historical wind structure of hurricanes that allows us, for the first time, to calculate the correlation of damage with the integrated wind profile of all hurricanes at landfall since 1988. We find that those metrics, which include the horizontal wind structure, rather than just maximum intensity, are better correlated with the hurricane cost. The vertical wind shear over the main development region of hurricanes plays a more dominant role than the sea surface temperature in controlling these metrics and therefore also ultimately the cost of hurricanes.
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Feldman, Michael A. "Efficient Low-Speed Flight in a Wind Field." Thesis, Virginia Tech, 1996. http://hdl.handle.net/10919/36527.
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A new software tool was needed for flight planning of a high altitude, low speed unmanned aerial vehicle which would be flying in winds close to the actual airspeed of the vehicle. An energy modeled NLP formulation was used to obtain results for a variety of missions and wind profiles. The energy constraint derived included terms due to the wind field and the performance index was a weighted combination of the amount of fuel used and the final time. With no emphasis on time and with no winds the vehicle was found to fly at maximum lift to drag velocity, Vmd. When flying in tail winds the velocity was less than Vmd, while flying in head winds the velocity was higher than Vmd. A family of solutions was found with varying times of flight and varying fuel amounts consumed which will aid the operator in choosing a flight plan depending on a desired landing time. At certain parts of the flight, the turning terms in the energy constraint equation were found to be significant. An analysis of a simpler vertical plane cruise optimal control problem was used to explain some of the characteristics of the vertical plane NLP results.Master of Science
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Carrion, Marina. "Low mach number CFD for wind turbine analysis." Thesis, University of Liverpool, 2014. http://livrepository.liverpool.ac.uk/2005639/.
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To maximise the amount of energy extracted from wind turbines, the rotor diameter has increased, reaching values of 160m in some cases. Large scale wind turbines are working at high Reynolds numbers and a wide range of flow conditions, with virtually incompressible flow present at the root and mildly compressible near the blade tips, where the Mach numbers can reach locally 0.48 for the largest wind turbines employed to date. In traditional aerodynamics, most CFD methods were designed to cope with high Mach number flows and consequently solve the compressible Navier-Stokes equations. This is the case of the Helicopter Multi-Block (HMB2) CFD method from Liverpool University. The present PhD thesis aims to provide an all-Mach-number capability to the HMB2 method, by implementing modified Roe schemes to account for low-Mach flows. For 2D cases, the modified Roe schemes showed great improvement in the convergence and the quality of the solution, when compared with the Original Roe and Osher schemes, and the Low-Mach Roe scheme showed the best performance. With the low-Mach capability included in the compressible solver, both MEXICO and NREL Annex XX experiments were simulated. A detailed analysis of the velocity field behind the MEXICO rotor was performed, where the low-Mach scheme (LM-Roe) showed less sensitivity on the grid size than the Osher scheme. Accurate prediction of wind turbine wake breakdown is also important for the performance analysis of the turbines and their optimal positioning within tightly-spaced wind farms. Using a fine mesh able to preserve the vortices up to 8R downstream the MEXICO rotor plane, the instabilities on the wake leading to vortex pairing were captured. FFTs of the axial velocity component enabled to identify the main harmonics in the wake. In the stable region, the wake was a perfect spiral and the main frequency was the bladepassing one. An approximate exponential growth was then observed and in the region where instabilities were present, higher frequencies dominated, leading an oscillatory pattern. Simple wake models were also investigated and a combination between a kinematic model to account for the wake initial expansion and a field model to account for the far wake decay was proposed, showing good agreement with the CFD solution. With the correct set of constants, it was proved that this simple model can be used to approximate the behaviour of wind turbine wakes with minimal computational cost. Another consequence of the increased size of wind turbines is that their stiffness lowers and aeroelasticity therefore plays an important role, since the blades can suffer great deformations. To account for the blade deformations, a tightly coupled CFD-CSD method was employed to analyse the MEXICO and NREL Annex XX wind turbines. For the latter, the tower and nacelle were considered as stiff bodies and the blades were allowed to deform. As a result of the aeroelastic calculations, the blades showed deformation in bending (towards the tower). The maximum deflections were present after the blades had passed in front of the tower, and maximum amplitudes of 0.59%R, at 20m/s were observed.
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Sangpanich, Umarin. "Optimization of wind-solar energy systems using low wind speed turbines to improve rural electrification." Thesis, University of Strathclyde, 2013. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=18944.
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Electricity is significant in improving the quality of life for people in rural and remote areas in developing countries. There are two main options for Rural Electrification (RE), namely grid extension and stand-alone systems. The governments and developers face the challenges of their limitations, namely technical, economic and environmental effects of each RE choice. This thesis intends to improve RE by focusing on renewable energy technologies, namely Wind Turbine (WT) and Photovoltaic (PV) systems. They have been developed and applied to RE because they are simple and environmentally friendly. They can be installed as separate units and they are sustainable alternative energy solutions. Installation, cost and performance are crucial issues of WT and PV applications, and are based on the terrain and climate where the renewable are installed. The efficiency of WTs and PV modules has increased, while their cost has declined continuously. However, a PV system still has installatio n costs around two times more expensive per watt than WTs. Most WTs using current technology can be financially worthwhile for high wind speed areas, having wind speeds greater than 6.4 m/s at 10 m hub height, but most rural areas have wind speeds of less than 6 m/s at the same height. Therefore, Low Wind Speed Turbines (LWSTs) have evolved, by increasing rotor diameter and while maintaining similar generator capacity. This is to reduce Levelized Cost of Energy (LCOE) for WTs in low wind speed areas. This thesis proposes simple cost models, namely the Sum-component cost model and the Total-cost model in order to calculate the LCOE of LWSTs. In addition, novel aspects of this thesis are that the optimization processes of stand-alone hybrid WT-PV systems and hybrid WT-PV systems using batteries at peak demand in remote area power systems provide simple, fast and flexible methods, by applying Multi-objective Evolutionary Algorithm (MOEA). The MOEA can analyze complex objective problems a nd provide an accurate multi-objective method. Results from relevant case studies show that the cost models and the optimization processes proposed are novel and are valuable tools for analysis and design, including the approaches for improving the system reliability and for estimating the Initial Capital Cost (ICC) of WTs having different rated wind speeds. The proposed algorithms are generic and can be utilized for other energy planning problems.
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Schmidt, Sarah Ruth. "Computational and wind tunnel studies of shelterbelts for reduction of wind flow and wind-induced loads on low-rise buildings." [Ames, Iowa : Iowa State University], 2008.
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Borujerdi, Javad. "Numerical evaluation of low-slope roofs for wind uplift." Thesis, University of Ottawa (Canada), 2004. http://hdl.handle.net/10393/26588.
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This dissertation contributes to an ongoing research project at the National Research Council Canada in the evaluation of roofing systems for wind uplift design. Accomplishments are grouped in two tasks. Task one provides development of a knowledge-based design module for the estimation of wind load distribution on roofs. Task two, numerical modeling using finite element methods and experiments to investigate the performance of roofing systems subjected to wind uplift loads.
For the Task one, all the data of wind uplift pressure distribution on roof configurations from open literature, including studies using wind tunnel boundary layer and full-scale measurements, are reviewed.
For the Task two, various mechanically attached single-ply roofing systems were numerically modeled based on the Finite Element program with the capability of non-linear analysis. Experiments were also carried out and data obtained from the Dynamic Roofing Facility was used for benchmarking the developed model. Since, there is no consensus on table size for evaluation of roofing system in various test procedures, the validated model was further used to investigate the effect of table size. (Abstract shortened by UMI.)
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Kumaresannair, Suresh Kumar. "Simulation of fluctuating wind pressures on low building roofs." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0007/NQ39782.pdf.
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Balaramudu, Vasanth Kumar. "Tornado-induced wind loads on a low-rise building." [Ames, Iowa : Iowa State University], 2007.
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15
Pietrzak, J. D. "Low frequency response of coastal waters to wind forcing." Thesis, Swansea University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.638531.
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The low frequency flow dynamics of the N.W. Aegean Sea, are investigated using a barotropic shelf circulation model, and by analysis of data from current meters deployed in Thermaikos Gulf. The performance of Groves (1955) and Lanczos-cosine filters is assessed to provide optimal low-pass filtering for the current meter records. The Lanczos-cosine filter is found to be the most effective in the present study. Time series and spectral analysis are applied to the filtered current meter records and to concurrent meteorological data. The results of these analyses show significant inputs of low frequency energy at periods of 2-4 days, 6-8 days and 20-26 days. An anomalous energy band exists that is uncorrelated with the wind and which is absent from one current meter record. The results from a depth-integrated momentum balance suggest that these bands are related to direct meteorological forcing. The 2-4 day band is related to 3-dimensional coastal water processes. The 6-8 day band is described in terms of internal Kelvin waves and the 20-26 day band is related to continental shelf waves. The anomalous band with 11-13 day period is associated with freshwater forcing from rivers. The low frequency shelf circulation of the Aegean Sea is modelled analytically. Solutions to the two-dimensional vorticity equation written in terms of stream functions are sought within a circular basin with exponential cross-shelf topography. The dispersion relations for the propagation of free waves is given. Introduction of the ageostrophic approximation allows solution to the wind-forced vorticity equation wherein, parameter separation leads to a wave equation soluble by the method of characteristics. The separation parameter is determined from the associated Sturm-Liouville equation. The damped wave problem is also solved. The model predicts the propagation of continental shelf waves, with periods of 20-26 days around the Aegean Sea.
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Claudepierre, Seth G. "Solar wind driving of magnetospheric ultra-low frequency pulsations." Connect to online resource, 2008. 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:3315834.
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Thesis (Ph.D.)--University of Colorado at Boulder, 2008.Source: Dissertation Abstracts International, Volume: 69-07, Section: B, page: 4214. Advisers: Scot R. Elkington; Keith Julien. Includes supplementary digital materials.
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Sehn, Kevin. "Aerodynamic mitigation of extreme wind loading on low-rise buildings." [Ames, Iowa : Iowa State University], 2008.
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Janajreh, Isam Mustafa II. "Wavelet Analysis of Extreme Wind Loads on Low-Rise Structures." Diss., Virginia Tech, 1998. http://hdl.handle.net/10919/30414.
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Over the past thirty years, extensive research has been conducted with the objective of reducing wind damage to structures. Wind tunnel simulations of wind loads have been the major source of building codes. However, a simple comparison of pressure coefficients measured in wind tunnel simulations with full-scale measurements show that the simulations, in general, underpredict extreme negative pressure coefficients. One obvious reason is the lack of consensus on wind tunnel simulation parameters.
The wind in the atmospheric surface layer is highly turbulent. In simulating wind loads on structures, one needs to simulate the turbulent character besides satisfying geometric and dynamic similitudes. Some turbulence parameters that have been considered in many simulations include, turbulence intensities, integral length scales, surface roughness, and frequency spectrum. One problem with these parameters is that they are time varying in the atmospheric boundary layer and their averaged value, usually considered in the wind tunnel simulations, cannot be used to simulate pressure peaks.
In this work, we show how wavelet analysis and time-scale representation can be used to establish an intermittency factor that characterizes energetic turbulence events in the atmospheric flows. Moreover, we relate these events to the occurrence of extreme negative peak pressures.Ph. D.
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Saha, Nilanjan. "Gap Size Effect on Low Reynolds Number Wind Tunnel Experiments." Thesis, Virginia Tech, 1999. http://hdl.handle.net/10919/35938.
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A system was designed to measure the effect of gap size on semi-span low Reynolds number wind tunnel experiments. The lift forces on NACA 1412, NACA 2412 and NACA 4412 half wings were measured using a strain gauge balance at chord Reynolds numbers of 100,000 and 200,000 and three different gap sizes including sealed gap. Pressure distributions on both airfoil top and bottom surfaces in the chord-wise direction near the gap were recorded for these airfoils. Also recorded was the span wise pressure distribution on both the airfoil surfaces at the quarter chord section. The results revealed that the presence of the gap, however small, affects the measurements. These effects were mainly observed in drop of lift and change in zero lift angle of attack and change in stall angle for the airfoil. The size of the gap is not linearly related to these changes, which also depend on the camber of the airfoil. These changes occur due to the flow through the gap from the lower surface to the upper surface of the model. The wing/end plate gap effect reduces along the span but is not fully restricted to the base of the model and the model behaves more like a full three-dimensional wing than a semi-span model. This study was made possible with the support of Department of Aerospace and Ocean Engineering, Virginia Polytechnic Institute and State University under the supervision of Dr. James MarchmanMaster of Science
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Joseph, Liselle AnnMarie. "Transition Detection for Low Speed Wind Tunnel Testing Using Infrared Thermography." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/78145.
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Transition is an important phenomenon in large scale, commercial, wind tunnel testing at low speeds because it is an excellent indicator of an airfoil performance. It is difficult to estimate transition through numerical techniques because of the complex nature of viscous flow. Therefore experimental techniques can be essential. Over the transition region the rate of heat transfer shows significant increases which can be detected using infrared thermography. This technique has been used predominantly at high speeds, on small models made of insulated materials, and for short test runs. Large scale testing has not been widely undertaken because the high sensitivity of transition to external factors makes it difficult to detect.
The present study records the process undertaken to develop, implement and validate a transition detection system for continual use in the Virginia Tech Stability Wind Tunnel: a low speed, commercial wind tunnel where large, aluminium models are tested. The final system developed comprises of two high resolution FLIR A655sc infrared cameras; four 63.5-mm diameter circular windows; aluminium models covered in 0.8-mm silicone rubber insulation and a top layer of ConTact© paper; and a series of 25.4-mm wide rubber silicone fiberglass insulated heaters mounted inside the model and controlled externally by experimenters. This system produces images or videos of the model and the associated transition location, which is later extracted through image processing methods to give a final transition location in percentage chord.
The system was validated using two DU96-W-180 airfoils of different chord lengths in the Virginia Tech Stability Wind Tunnel, each tested two months apart. The system proved to be robust and efficient, while not affecting the airfoil performance or any other system in use in the wind tunnel. Transition results produced by the system were compared to measurements obtained from pressure data and stethoscope tests as well as the numerical predictions of XFOIL. The transition results from all four methods showed excellent agreement with each other for the two models, for at least two Reynolds numbers and for several angles of attack on both suction and pressure side of the model. The agreement of data obtained under such different conditions and at different times suggests that the infrared thermography system efficiently and accurately detects transition for large aluminium models at low speeds.Master of Science
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Gough, Tim. "Low Reynolds number turbulent boundary layers and wakes." Thesis, University of Surrey, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360949.
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Burton, Melissa Deanne. "Effects of low frequency wind-induced building motion on occupant comfort." online access from Digital Dissertation Consortium, 2006. http://libweb.cityu.edu.hk/cgi-bin/er/db/ddcdiss.pl?3268726.
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Dagnew, Agerneh. "Computational Evaluation of Wind Loads on Low- and High- Rise Buildings." FIU Digital Commons, 2012. http://digitalcommons.fiu.edu/etd/802.
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Buildings and other infrastructures located in the coastal regions of the US have a higher level of wind vulnerability. Reducing the increasing property losses and causalities associated with severe windstorms has been the central research focus of the wind engineering community. The present wind engineering toolbox consists of building codes and standards, laboratory experiments, and field measurements. The American Society of Civil Engineers (ASCE) 7 standard provides wind loads only for buildings with common shapes. For complex cases it refers to physical modeling. Although this option can be economically viable for large projects, it is not cost-effective for low-rise residential houses.
To circumvent these limitations, a numerical approach based on the techniques of Computational Fluid Dynamics (CFD) has been developed. The recent advance in computing technology and significant developments in turbulence modeling is making numerical evaluation of wind effects a more affordable approach. The present study targeted those cases that are not addressed by the standards. These include wind loads on complex roofs for low-rise buildings, aerodynamics of tall buildings, and effects of complex surrounding buildings. Among all the turbulence models investigated, the large eddy simulation (LES) model performed the best in predicting wind loads. The application of a spatially evolving time-dependent wind velocity field with the relevant turbulence structures at the inlet boundaries was found to be essential. All the results were compared and validated with experimental data. The study also revealed CFD’s unique flow visualization and aerodynamic data generation capabilities along with a better understanding of the complex three-dimensional aerodynamics of wind-structure interactions.
With the proper modeling that realistically represents the actual turbulent atmospheric boundary layer flow, CFD can offer an economical alternative to the existing wind engineering tools. CFD’s easy accessibility is expected to transform the practice of structural design for wind, resulting in more wind-resilient and sustainable systems by encouraging optimal aerodynamic and sustainable structural/building design. Thus, this method will help ensure public safety and reduce economic losses due to wind perils.
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Primeau, François W. (François William) 1966. "Multiple equilibria and low-frequency variability of wind-driven ocean models." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/58512.
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Thesis (Ph. D.)--Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 1998.Includes bibliographical references (leaves 156-158).
by François W. Primeau.
Ph.D.
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Wise, John Nathaniel. "Optimization of a low speed wind turbine using support vector regression." Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/2737.
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Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2009.NUMERICAL design optimization provides a powerful tool that assists designers in improving their products. Design optimization automatically modifies important design parameters to obtain the best product that satisfies all the design requirements. This thesis explores the use of Support Vector Regression (SVR) and demonstrates its usefulness in the numerical optimization of a low-speed wind turbine for the power coe cient, Cp. The optimization design problem is the three-dimensional optimization of a wind turbine blade by making use of four two-dimensional radial stations. The candidate airfoils at these stations are selected from the 4-digit NACA range. A metamodel of the lift and drag coe cients of the NACA 4-digit series is created with SVR by using training points evaluated with XFOIL software. These SVR approximations are used in conjunction with the Blade Element Momentum theory to calculate and optimize the Cp value for the entire blade. The high accuracy attained with the SVR metamodels makes it a viable alternative to using XFOIL directly, as it has the advantages of being faster and easier to couple with the optimizer. The technique developed allows the optimization procedure the freedom to select profiles, angles of attack and chord length from the 4-digit NACA series to find an optimal Cp value. As a result of every radial blade station consisting of a NACA 4-digit series, the same lift and drag metamodels are used for each station. This technique also makes it simple to evaluate the entire blade as one set of design variables. The thesis contains a detailed description of the design and optimization problem, the implementation of the SVR algorithm, the creation of the lift and drag metamodels with SVR and an alternative methodology, the BEM theory and a summary of the results.
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Jeyaratnam, Jonathan Jehan. "On the low speed longitudinal stability of hypersonic waveriders." Thesis, The University of Sydney, 2020. https://hdl.handle.net/2123/22456.
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The development of hypersonic civilian transport aircraft requires solutions to a number of challenging problems in the areas of aerothermodynamics, control, aeroelasticity, propulsion and others encountered at high Mach number flight. The desire for good aerodynamic performance at high Mach numbers results in slender vehicle designs called waveriders. The stability and handling of waverider shapes at the low speeds at the take-off and landing phases of flight is not well studied. This thesis covers static and dynamic CFD simulations of the Hexafly-Int glider which have been used to obtain longitudinal stability derivatives at low speeds. Complementary static and free-to-pitch dynamic wind tunnel testing, are used to validate the CFD computations. A final chapter on the optimisation of waverider designs including low speed longitudinal stability is presented to show the impacts of this additional requirement on the hypersonic design space. The static wind tunnel testing has identified stability issues relating to the location of the centre of gravity. The design centre of gravity which is suitable for the Hexafly-Int vehicle at Mach 7.2 is found to be too far aft which results in instability at low speeds. In addition, the dynamic testing in the wind tunnel shows that the pitch damping is inadequate at low speeds. The CFD simulations agree well with the wind tunnel test results validating the use of CFD tools for determining dynamic stability derivatives of this class of slender vehicle in the design process. To alleviate the low speed stability issue of hypersonic vehicles, a waverider shape optimisation study has been carried out to understand what shapes will produce better low speed stability behaviour. These shapes are found to produce lower aerodynamic efficiency at high speeds which suggests that a design compromise between low speed stability and high speed performance is required at the outset of hypersonic waverider design.
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Elzaidabi, Abdalla Ali Mohamed. "Low energy, wind catcher assisted indirect-evaporative cooling system for building applications." Thesis, University of Nottingham, 2009. http://eprints.nottingham.ac.uk/10703/.
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Increased consciousness of the environmental problems has aroused people’s interest of renewable energy systems, especially the application of green features in buildings. The demand for air conditioning / cooling in domestic and non-domestic buildings is rising throughout the world; this increases the reliance on conventional fuels and the global warming effect from greenhouse gas emissions. Passive cooling and energy efficient design can substantially reduce reliance on fuel based heating and cooling. Passive and Hybrid Downdraught Cooling, in different forms, is now technically viable in many parts of the world. This has been established through a combination of research projects. In some hot arid regions, a major part of the energy consumed consists of air-conditioning requirements. Alternative methods, using passive cooling techniques, can assist in reducing the conventional energy consumption in buildings. Evaporative cooling, which can be tracked back several hundreds of years in ancient Egypt and Persia [1–3], is one of the most effective strategies, because of the enormous latent heat needed for evaporation of water. Green features are architectural features used to mitigate migration of various air-borne pollutants and transmission of air from outside to indoor environment in an advantageous way [9]. The reduction of fossil fuel consumption and the associated decrease in greenhouse gas emissions are vital to combat global warming and this can be accomplished, in part, by the use of natural ventilation. To assess the performance of several innovative cooling systems devices and to develop improved models for more established technology, quantitative measurement of output was necessary. This was achieved in this study by the development of simply constructed low energy cooling systems which were calibrated by the innovative use of wind and water as a source. These devices were found to be consistent and accurate in measuring the temperature and cooling load from a number of devices. There were some problems in the original evaporative units. Therefore, a number of modifications have to be made to enhance the systems performance. The novel Windcatcher – PEC cooling system was assessed and different cooling loads were achieved.
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Copland, Christopher M. "The generation of transverse and longitudinal vortices in low speed wind tunnels." Thesis, University of Glasgow, 1997. http://theses.gla.ac.uk/2543/.
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The present study documents an experimental and numerical investigation into the feasibility of generating longitudinal and transverse vortices in low speed wind tunnels. The longitudinal vortex system is that of a co-rotating vortex pair which, if substituted for a classical single tip vortex, may produce a beneficial modification to Blade Vortex Interaction. The transverse vortex mimics the tip vortex of a typical helicopter rotor and may be used to assess its effect when interacting with other aerofoils or fuselage components. Experiments have been conducted to investigate the flow field associated with two co-rotating vortices which represent the idealised vortex system associated with a novel rotor blade tip platform - the Westland Helicopters Vane Tip. These vortices were generated by two rectangular NACA 0015 half wings positioned upstream of the working section of a low speed wind tunnel. Hot-wire measurements were conducted downstream of the generators using x-wire probes to document the strength, position and size of the vortices. A numerical model was utilised to provide an accurate means of determining vortex strength, position and size. Finally, the model was successfully extended to consider the rotation of the vortex system. The transverse vortex was generated by a rotating blade placed in the contraction of a low speed wind tunnel. A numerical model was utilised in the conceptual design of the experimental facility to model the flow through the settling chamber, contraction, working section and diffuser. This numerical model consisted of a three dimensional source panel method, used to calculate the constrained flow through the low speed tunnel, and a free wake model representing the wake generated by the vortex generator. Convection of the wake was determined by superposition of the undisturbed tunnel velocity and the induced velocity components from the wake itself. Results, obtained via a parametric analysis, illustrate the relationship between the geometry of the wake and basic physical design parameters. On this basis, two possible operational strategies for the upstream rotor are examined with reference to development of the experimental facility. It is concluded that, while a short duration finite rotor traverse may be the optimum vortex generation strategy, a continuous running rotor is a more cost effective and viable option.
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Ibrahim, Rania Assem Elsayed. "Low voltage ride-through of permanent magnet synchronous generator wind energy systems." Thesis, University of Strathclyde, 2014. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=24907.
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Low Voltage Ride-Through (LVRT) capability is considered a critical feature that should be implemented within a Wind Energy Conversion System (WECS). The mismatch produced between the generated active power and the power delivered to the grid during any dip incidence at the Point of Common Coupling causes a dc link voltage rise, and increase in grid currents and generator speed-up. Failure to ride-through grid voltage dips would lead to converter failures within the WECS. This thesis focuses on enhancing LVRT capability of PMSG based WECS using magnetic amplifiers. LVRT techniques vary according to the turbine and utility grid variables. A survey of the state-of-art LVRT techniques highlighting the merits and demerits of each approach is carried out. A 1.5 MW wind turbine system is modelled, which includes the wind turbine, PMSG, and power converters. Also PMSG control, maximum power point extraction, and grid active and reactive power control are investigated. System performance is studied in compliance with British grid codes for active and reactive power sudden changes, frequency excursion, and grid voltage phase angle jump. The model is tested for LVRT capability under symmetrical network dips. Magnetic amplifiers have been used in various applications such as instrumentation, fault current limiting, and battery chargers. In this thesis, magnetic amplifiers are proposed as part of a LVRT capability enhancing technique. Two possible configurations are proposed; 3-phase and dc-side configurations. LVRT capability enhancement is investigated for the 1.5MW WECS using the two magnetic amplifier configurations. The 3-phase topology is able to reduce the dc link voltage rise; however, it causes an increase in the stored rotor inertia accompanied by an increase in generator speed. The dc-side magnetic amplifier topology is able to limit the dc-link voltage rise which in turn protects the power converters without affecting generator performance. In addition to simulations, a scaled prototype with the dc side magnetic amplifier configuration is used to verify the effectiveness and applicability of the proposed technique during steady state and transient behaviour under various operating conditions.
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Wang, Yuchen. "Blade Design of Vertical Axis Wind Turbine at Low Tip-speed-ratios." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1524224348317784.
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Ross, Ian Jonathan. "Wind Tunnel Blockage Corrections: An Application to Vertical-Axis Wind Turbines." University of Dayton / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1271306622.
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Worasinchai, Supakit. "Small wind turbine starting behaviour." Thesis, Durham University, 2012. http://etheses.dur.ac.uk/4436/.
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Small wind turbines that operate in low-wind environments are prone to suffer performance degradation as they often fail to accelerate to a steady, power-producing condition. The behaviour during this process is called “starting behaviour” and it is the subject of this present work. This thesis evaluates potential benefits that can be obtained from the improvement of starting behaviour, investigates, in particular, small wind turbine starting behaviour (both horizontal- and vertical-axis), and presents aerofoil performance characteristics (both steady and unsteady) needed for the analysis. All of the investigations were conducted using a new set of aerodynamic performance data of six aerofoils (NACA0012, SG6043, SD7062, DU06-W-200, S1223, and S1223B). All of the data were obtained at flow conditions that small wind turbine blades have to operate with during the startup - low Reynolds number (from 65000 to 150000), high angle of attack (through 360◦), and high reduced frequency (from 0.05 to 0.20). In order to obtain accurate aerodynamic data at high incidences, a series of CFD simulations were undertaken to illustrate effects of wall proximity and to determine test section sizes that offer minimum proximity effects. A study was carried out on the entire horizontal-axis wind turbine generation system to understand its starting characteristics and to estimate potential benefits of improved starting. Comparisons of three different blade configurations reveal that the use of mixed-aerofoil blades leads to a significant increase in starting capability. The improved starting capability effectively reduces the time that the turbine takes to reach its power-extraction period and, hence, an increase in overall energy yield. The increase can be as high as 40%. Investigations into H-Darriues turbine self-starting capability were made through the analogy between the aerofoil in Darrieus motion and flapping-wing flow mechanisms. The investigations reveal that the unsteadiness associated with the rotor is key to predicting its starting behaviour and the accurate prediction can be made when this transient aerofoil behaviour is correctly modelled. The investigations based upon the analogy also indicate that the unsteadiness can be exploited to promote the turbine ability to self-start. Aerodynamically, this exploitation is related to the rotor geometry itself.
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Bykerk, Tamas. "Low Speed Aerodynamics, Performance and Handling Qualities of a Hypersonic Waverider." Thesis, University of Sydney, 2020. https://hdl.handle.net/2123/23111.
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Interest in the development of high speed commercial aircraft capable of travelling in excess of Mach 5 is on the increase. This is mainly driven by the potential of these vehicles to significantly reduce long haul flight times, connecting antipodal city pairs such as Brussels and Sydney in less than three hours. The hypersonic waverider concept has received particular attention because of its ability to achieve comparatively high aerodynamic efficiency at hypersonic cruise, as the body shock is contained by the wing leading edges. As research into the extreme conditions at high Mach numbers takes priority, no full subsonic handling quality analysis of a waverider has ever been completed, nor has an understanding of the mechanisms behind both static and dynamic stability been developed. This gap in literature is addressed by this thesis, which presents a combination of results from computational fluid dynamics simulations and wind tunnel experiments, completing the first full subsonic handling quality analysis of a waverider.
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Harley, Christopher Donald. "Aerodynamic performance of low form factor spoilers." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/aerodynamic-performance-of-low-form-factor-spoilers(1d16d656-3f9e-48de-8272-bce587ba64e4).html.
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The development of low form factor flight controls is driven by the benefits of reducing the installed volume of the control device and/or minimising the change in external geometry, with particular application to flight control of low observable aircraft. For this work, the term "low form factor" does not refer to the aspect ratio of the control device rather the overall installed volume. This thesis compares the use of low form factor geometric and fluid devices on a NACA 0015 aerofoil section through two-dimensional numerical analysis and low speed wind tunnel experiments. The geometric spoiler is implemented as a small (boundary layer scale) variable height tab oriented normal to the local surface, referred to as a Micro Geometric Spoiler (MiGS). The fluidic spoiler is implemented as an air jet tangential to the local surface acting in the forward direction, referred to as a Counter-Flow Fluidic Spoiler (CFFS). Two chordwise spoiler locations were considered: 0.35c and 0.65c. Numerical analysis was undertaken using a commercial CFD code using an unsteady solver and k-omega shear-stress-transport turbulence model. Experimental forces and moments were measured via an overhead force balance, integrated surface pressures and pressure wake survey. Device performance is assessed against the magnitude of control achievable compared to macro scale spoilers and trailing edge controls (effectiveness), the ratio of aerodynamic output to control input (efficiency or gain), the shape of control response curve (linearity), and the degree of control cross coupling. Results show that the MiG and CFF spoilers work by a similar mechanism based on inducing flow separation that increases the pressure ahead of the spoiler and reduces the pressure downstream. Increasing control input increases drag and reduces lift, however the change in pitching moment is dependent on chordwise location. Chordwise location has a significant effect on effectiveness, efficiency, linearity and separability. Forward MiGS location gives the largest drag gain however the control response is strongly nonlinear with angle of attack and there is a significant undesirable coupling of drag with pitching moment. Aft MiGS location significantly improves control linearity and reduces pitching moment coupling however the drag gain is much reduced. For the CFFS, the control linearity with respect to control input and angle of attack is good for both forward and aft locations, with the aft location giving the largest gain for lift and drag. The control response trends predicted from numerical analysis are good, however a calibration factor of around ½ has to be applied to the control input momentum to match the experimentally observed gains. Furthermore numerical control drag polars under predict the change in lift with change in drag at low blowing rates. Through the use of a CFFS device on both the upper and lower surfaces of a wing section it is possible to generate control drag inputs fully decoupled from both lift and pitching moment, thus potentially simplifying device control law implementation within an integrated yaw control system.
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Hinneburg, Detlef. "The calculation of a wind climatology of the Erzgebirge." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-212336.
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Ausgangspunkt für die Berechnung klimatologisch gemittelter Windgeschwindigkeiten ist die mesoskalige Simulation atmosphärischer Strömungsereignisse, die von der geostrophischen Windgeschwindigkeit gesteuert werden. Der geostrophische Wind wird in 8 Richtungssektoren und Betragsklassen zu je 5m/s eingeteilt, so daß für jeden Sektor bis zu 7 Simulationen auszuführen waren. Die Simulationen wurden mit dem nicht-hydrostatischen Modell GESIMA für eine adiabatisch geschichtete Atmosphäre durchgeführt. Die statistische Mittelung der berechneten Werte erfolgte mit Hilfe einer 10-jährigen Häufigkeitsverteilung des 850hPa-Windes der Radiosondenmessungen von Prag. Ein Vergleich mit den Beobachtungswerten einiger Bodenstationen ergibt Abweichungen bis zu lm/s über höheren BergenStarting from the classification of the geostrophic wind into 8 sectors each of them splitted up into 7 classes by 5m/s, simulations with the non-hydrostatic mesoscale atmospheric model GESIMA were performed assuming adiabatic stratification of the atmosphere for each class. The climatologically averaged wind velocities are obtained by the folding with a ten-years frequency distribution of the geostrophic wind measured by the radio sonde station of Prague. Wind velocities observed at some surface stations indicate, that the simulated values can deviate from them by up to lm/s on high mountains
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Ksiazek, Peter F. "Reduction of current/torque ripple in low power grid-tie PMSG wind turbines." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/50298.
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Small-scale Wind Energy Conversion Systems (WECS) are becoming an attractive option for distributed and renewable energy generation. In order to be affordable, WECS must have low capital and maintenance costs. This leads to the increasing penetration of Permanent Magnet Synchronous Generators (PMSG) operating at variable frequency with connections to the power grid through a rectifier, and grid-tie inverter. Because PMSGs lack brushes and can be directly coupled to wind turbines, the capital and maintenance costs are greatly reduced. A direct connection to the grid further reduces system costs by removing the requirement of large battery banks.
The loading produced by grid-tie inverters on the DC bus is different than more typical constant-current or constant-power loads. They are characterized by large input ripple currents at twice the inverter's grid frequency. These ripple currents are reflected through the DC bus into the PMSG causing increased heating in the stator, and ripple torques which lead to premature bearing failure and increased maintenance costs. To mitigate this problem, manufacturers typically add large amounts of capacitance on the DC bus to partially absorb these ripples at the expense of system size, cost, and reliability.
In this work, the effects of the grid-tie inverter load are explored using system behavioural models which provide insight into the low frequency behaviour of the PMSG, rectifier, DC bus, and inverter. The swinging bus concept is presented and analysed in the time and frequency domains. A control philosophy is developed which allows the DC bus to swing, thus removing the effects of the grid-tie inverter on the PMSG while keeping the DC bus capacitor small. A solution consisting of a Moving Average Filter (MAF) is presented as an integral part of the control strategy.
Full simulations of a complete system are developed and investigated to verify the ripple torque reduction technique. Finally, a prototype is developed and experimental results are presented for a 2.5kW PMSG turbine generator. The simulation and experimental results are compared to a traditional controller showing tangible improvements in ripple current and torque in the PMSG, while improving the dynamic response of the system.Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate
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Young, Michael A. "Effect of open fields on low building wind loads in a suburban environment." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq28694.pdf.
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Steinhoff, Daniel Frederick. "Cyclogenesis near the Adélie coast and influence of the low-level wind regime." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1204812781.
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Dalley, Sam. "Wind tunnel measurements on a low rise building and comparison with full-scale." Thesis, University of Surrey, 1993. http://epubs.surrey.ac.uk/886/.
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Cencelli, Nicolette Arnalda, Bakstrom T. W. Von, and T. S. A. Denton. "Aerodynamic optimisation of a small-scale wind turbine blade for low windspeed conditions." Thesis, Stellenbosch : Stellenbosch University, 2006. http://hdl.handle.net/10019.1/353.
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Thesis (MScEng (Department of Mechanical and Mechatronic Engineering))--Stellenbosch University, 2006.ENGLISH ABSTRACT: Wind conditions in South Africa determine the need for a small-scale wind turbine to produce useable power at windspeeds below 7m/s. In this project, a range of windspeeds, within which optimal performance o the wind turbine is expected, was selected. The optimal performance was assessed in terms of the Coefficient of Power(Cp), which rates the turbines blade's ability to extract energy form the avalible wind stream. The optimisation methods employed allowed a means of tackling the multi-variable problem such that the aerodynamic characteristics of the blade were ideal throughout the wind speed range. The design problem was broken down into a two-dimensional optimisaion of the airfoils used at the radial stations, and a three-dimensional optimisation of the geometric features of the wind rotor. by means of blending various standard airfoil profiles, a new profile was created at each radial station. XFOIL was used for the two-dimensional analysis of these airfoils. Three-dimensional optimisn involved representation of the rotor as a simplified model and use of the Blade Element Momentum(BEM) method for analysis. an existimg turbine blade, on which the design specifications were modelled, was further used for comparative purposes throughout the project. The resulting blade design offers substantial improvements on the reference design. The application of optimisation methods has successfully aided the creation of a wind turbine blade with consistent peak performance over a range of design prints.
Sponsored by the Centre for Renewable and Sustainable Energy Studies, Stellenbosch University
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Khan, Md Shahrukh Adnan. "Low cost vertical axis wind energy harvesting system using supercapacitors for rural Malaysia." Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/40586/.
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Numerous countries worldwide are conscious about the fact that the past and current trends of energy system are not sustainable and a solution needs to be drawn to protect the world energy from a drastic falling. One of the sources that can replace the current trend is surely wind energy that momentously depends on the availability of the wind resource. For a typical horizontal axis wind turbine to run and generate power, a wind speed of at least 5 m/s is required. Countries like Malaysia have less than 5m/s average wind speed. Another predicament is that these regions face unsteady multi-directional winds making HAWT totally incompatible in such areas. The vertical axis wind turbine on the other hand is appropriate for such regions due to its ability to capture wind energy at any direction. Also, the use of Neodymium magnets for suspension at the bottom surface assist attaining nearly zero friction (Maglev), could be of help improving the output efficiency. Conventional generators now-a-days have been replaced with Permanent Magnet Synchronous Generator (PMSG). Although a number of researches in the area of VAWT and PMSG are carried through separately, few attempts were taken to build a system that work efficiently at low wind speed. Moreover, there is another gap in research for an off-grid standalone energy harvesting device incorporated with low wind Maglev VAWT. This thesis provides a platform for a novel innovative approach towards an off-grid energy harvesting system (EHS) for Maglev VAWT. This EHS basically a Supercapacitor based hybrid battery charging energy harvesting device. Rural areas in countries like Malaysia where grid connection is not always available, this standalone system there can make a difference for small scale electronic devices. In this thesis, a complete simulation analysis is done for all 3 types of PMSG connected to VAWT and result was compared. This novel comparison showed that 5-phase is a better performer both in high and low speed comparing with 3-phase and dual stator. Moreover, although at high speed dual stator provides better power efficiency than 3-phase, at low wind, output power performance in 3-phase surpasses that of dual stator. At low wind, even though 5-phase PMSG shows better performance in low wind speed, 3-Phase PMSG was chosen for low maintenance cost, light weight and less complicated design. With the variation of design parameters under low wind speeds, two configurations were optimized for rural Malaysia in terms of low speed, high power and output torque. First configuration was a 1.5KW 220V 20 Pole AFPMSG adopted to a Maglev based VAWT having radius and height of 1m and 2.6m respectively. The other configuration presents a 200W 12V 16 Pole AFPMSG attached to Maglev VAWT of 14.5cm radius and 60cm of height. Later weight to Power Ratio is applied subsequently and the second configuration has been proved to be more cost-effective. The proposed system was also compared with existing models in rural Malaysia for cost-efficiency. A prototype version of the low cost optimized system is built up in lab for open circuit performance and with satisfactory findings, design is sent for fabrication. Upon arrival, the optimized system is implemented into the energy harvesting circuit and field testing is carried to observe the performance. The energy harvesting circuit shows better efficiency in charging battery in all aspects comparing to direct charging of battery regardless of with or without converter. Sufficient groundwork and results have been laid out in this thesis to deliver the necessary development and framework for further improvements. Based on analysis and results carried out in this thesis, all feasibility studies and information are provided for the next barrier.
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Gomez, Martinez Jonathan. "Investigating the flexibility of low-carbon power systems : wind variability and carbon capture." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/investigating-the-flexibility-of-lowcarbon-power-systems-wind-variability-and-carbon-capture(3df46bcf-aa09-4ed2-b528-1c473900ba37).html.
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Increasing concerns about global warming have led to the exploration of options to abate CO2 emissions. Recent studies have identified the energy sector as the largest emitting source worldwide. Therefore, the transition towards low-carbon power systems has incorporated larger volumes of renewable generation. This situation is prompting the necessity of improving current strategies to operate power systems, as more variability is introduced in the decision making process. This thesis contributes in two aspects to manage the generation mix of future power systems. Firstly, it addresses the question of how many scenarios are enough to represent the variability of wind power. Results obtained indicate that a balance should be pursued between quality of solution and computational burden, as more scenarios does not significantly change the operational cost. Secondly, an original method to narrow down the number of scenarios is proposed. The so-called severe scenarios outperform typical reductions in the sense that fewer adjustments are required to the generation scheduling programme. Despite the growing renewable generation capacity, the operation of the electric system is likely to continue its reliance on thermal plants. Hence, the need to curb CO2 emissions in the existing thermal plants has led to the development of technologies such as carbon capture. The technical maturity of this technology is still in its early stages, since its application to thermal plants is under development. This thesis bridges the gap of current knowledge on carbon capture in three aspects. Firstly, it presents an innovative methodology to quantify the value of flexibility provided by carbon capture in the context of the British system. Secondly, the role of retrofitted generators as reserve providers is addressed. Finally, the synergy between carbon capture and wind power is assessed. The evaluation considers CO2 pricing, two strategies to manage CO2 capture rate, variability and different levels of wind integration.
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Steinhoff, Daniel Frederick. "Cyclogenesis Near the Adélie Coast and Influence of the Low-level Wind Regime." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1204812781.
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Antonutti, Raffaello. "Numerical study of floating wind turbines : hydro- and aero-mechanics." Thesis, University of Edinburgh, 2016. http://hdl.handle.net/1842/16530.
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Floating wind technology has the potential to produce low-carbon electricity on a large scale: it allows the expansion of o shore wind harvesting to deep water, indicatively from 50-60 to a few hundred metres depth, where most of the worldwide technical resource is found. New design specifi cations are being developed for floating wind in order to meet diverse criteria such as conversion effi ciency, maintainability, buoyancy stability, and structural reliability. The last is the focus of this work. The mechanics of floating wind turbines in wind and waves are investigated with an array of numerical means. They demand the simulation of multiple processes such as aerodynamics, hydrodynamics, rotor and structural dynamics; understanding their interaction is essential for engineering design, verifi cation, and concept evaluation. The project is organised in three main parts, presented below. Aero-hydro-mechanical simulation, characterising the rigid-body motions of a floating wind turbine. An investigation of multi-physical couplings is carried out, mainly through EDF R&D's time-domain simulator CALHYPSO. Wave forces are represented with the potential- ow panel method and the Morison equation. Aerodynamic forces are represented by a thrust model or with the blade element momentum theory. Main fi ndings: Exposure of fi nite-angle coupling for semi-submersible turbines with focus on heave plate excursion; characterisation of the aerodynamic damping of pitch motion provided by an operating vertical-axis turbine. Dynamic mooring simulation, focussed on highly compliant mooring systems, where the fluid-structure interaction and mechanical inertial forces can govern line tension. EDF R&D's general-purpose, finite-element solver Code Aster is confi gured for this use exploiting its nonlinear large-displacement and contact mechanics functionalities. Main findings: Demonstration of a Code Aster-based work ow for the analysis of catenary mooring systems; explanation of the dynamic mooring eff ects previously observed in the DeepCwind basin test campaign. Aeroelastic analysis of vertical-axis rotors, aimed at verifying novel large-scale floating wind turbine concepts in operation, when aeroelastic-rotordynamic instabilities may occur. The finite-element modal approach is used to qualify rotor vibrations and to estimate the associated damping, based on the spinning beam formulation and a linearised aerodynamic operator. Main fi ndings: Characterisation of the vibration modes of two novel vertical-axis rotor concepts using the Campbell diagram; estimation of the related aerodynamic damping, providing information on the aeroelastic stability of these designs.
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Arnold, Klaus, Armin Raabe, and Gerd Tetzlaff. "Regionale Unterschiede im Auftreten von Eisablagerungen." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-212389.
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Bei der Errichtung von Windenergieanlagen in Mittelgebirgsregionen ist darauf zu achten, daß an windexponierten Standorten die Gefahr einer Vereisung der Rotorblätter besteht. Es wurden klimatologische Daten im Bereich der Mittelgebirge ausgewertet und daraus eine Karte erarbeitet, in der die jährliche mittlere Häufigkeit der Tage mit Eisablagerungen dargestellt istWith the installation of wind turbines in low mountain areas the hazard of ice accretions on rotor blades at windy places must be considered. Interpreting climatological datas of the low mountain areas of S. E. Germany a map has been produced which shows the annual frequencies of days ice accretions on structures occurs
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Cedrun, Mark E. "Low-speed wind tunnel testing of the NPS/NASA Ames Mach 6 optimized waverider." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1994. http://handle.dtic.mil/100.2/ADA283585.
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Thesis (M.S. in Aeronautical Engineering)--Naval Postgraduate School, June 1994.Thesis advisor(s): Conrad F. Newberry, Jeffrey V. Bowles. "June 1994." Includes bibliographical references. Also available online.
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Lemmer, Frank [Verfasser]. "Low-order modeling, controller design and optimization of floating offshore wind turbines / Frank Lemmer." München : Verlag Dr. Hut, 2018. http://d-nb.info/1174425768/34.
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Baker, Jonathan. "An optimal, low-cost design for small wind turbine converters applied to charging batteries." Honors in the Major Thesis, University of Central Florida, 2009. http://digital.library.ucf.edu/cdm/ref/collection/ETH/id/1232.
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This item is only available in print in the UCF Libraries. If this is your Honors Thesis, you can help us make it available online for use by researchers around the world by following the instructions on the distribution consent form at http://library.ucf.edu/Systems/DigitalInitiatives/DigitalCollections/InternetDistributionConsentAgreementForm.pdf You may also contact the project coordinator, Kerri Bottorff, at kerri.bottorff@ucf.edu for more information.Bachelors
Engineering and Computer Science
Electrical Engineering and Computer Science
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Hamilton, Christopher. "Digital control algorithms : low power wind turbine energy maximizer for charging lead acid batteries." Honors in the Major Thesis, University of Central Florida, 2009. http://digital.library.ucf.edu/cdm/ref/collection/ETH/id/1280.
Full textAbstract:
This item is only available in print in the UCF Libraries. If this is your Honors Thesis, you can help us make it available online for use by researchers around the world by following the instructions on the distribution consent form at http://library.ucf.edu/Systems/DigitalInitiatives/DigitalCollections/InternetDistributionConsentAgreementForm.pdf You may also contact the project coordinator, Kerri Bottorff, at kerri.bottorff@ucf.edu for more information.Bachelors
Engineering and Computer Science
Electrical Engineering and Computer Science
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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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