Dissertations / Theses on the topic 'Aerodynamics'
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1
Vančura, Jan. "Výpočet aerodynamiky závodního automobilu." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2008. http://www.nusl.cz/ntk/nusl-228231.
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The main subject of this diploma thesis is computation of race car aerodynamics. It describes composition method of CFD model with utilization of 3D scanner ATOS and CAD software Pro Engineer. During creating this diploma thesis were found influences of additional aerodynamics components of racing car on globally axle loads.
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Lång, Marcus. "CFD-Method for 3D Aerodynamic Adjoint Simulations : For External Automotive Aerodynamics." Thesis, Linköpings universitet, Mekanisk värmeteori och strömningslära, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-158624.
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Today’s rules and regulations regarding emissions from combustion vehicles are very strict and the travel range per tank and/or charge, especially for electric vehicles, is a crucial factor which will always be considered by the customers. Hence, automotive manufacturers strive to boost fuel and battery economy. This can, to a great extent, be done by improving the aerodynamics of the vehicle for lower drag. The conventional CFD process for aerodynamic development is relatively time consuming and there is rarely enough timeor resources to find the optimal design in all regions of the vehicle. Hence, the adjoint solver was investigated to make the aerodynamic development process more efficient by providing sensitivities of the geometry with respect to drag force. The adjoint solver was investigated both through a literature review as well as by performing CFD and adjoint simulations. The CFD and adjoint simulations were performed using Fluent 2019 R1 and the realizable k-ε turbulence model. It was found that it is important to monitor surface sensitivities during the solution in addition to the adjoint residuals to assess convergence of the adjoint simulation. It is also recommended to analyse regions of high residuals in the domain to ensure that they are far away from the surface(s) of interest. Investigations regarding different stabilization schemes as well different meshes for the adjoint solver were performed. It was concluded that the residual minimization scheme (RMS) is the preferred stabilization scheme. It was found that a coarser mesh can be used to reduce localized transient behaviour if the adjoint solver has trouble converging. It was found that a simplified model of a fully detailed car geometry is necessary to reduce the complexity and the resolution of the mesh to be able to use the RMS and to avoid local instabilities. A proposed CFD and adjoint procedure with guidelines and recommendation was developed.
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Poláš, Maroš. "Experimentální identifikace aerodynamických vlastností vozidla jízdní zkouškou." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2017. http://www.nusl.cz/ntk/nusl-319863.
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This thesis deals with road loads, coastdown tests and evaluation of measured data. Thesis consists of two main parts: theoretical and computational. The first part describes road loads with focus on aerodynamic drag and lift force. In the second part, a software tool for processing the measurement per ISO 10521-1 is designed and lift force measured with running resistance method is calculated.
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McNabb, Michael Lynn. "Development of a cycloidal propulsion computer model and comparison with experiment." Master's thesis, Mississippi State : Mississippi State University, 2001. http://library.msstate.edu/etd/show.asp?etd=etd-08032001-111940.
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Wakeling, James Michael. "Dragonfly aerodynamics." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243066.
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Barman, Emelie. "Aerodynamics of Flutter." Thesis, KTH, Mekanik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-34152.
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The unsteady ow around an aerofoil placed in a uniform ow stream with an angle of attack is investigated, under the assumption of inviscid, incompressible, two-dimensional flow. In particular, a function of the velocity jump over the wake is achieved, where this function depends on the horizontal displacement and time. The aerofoil geometry is represented by two arbitrary functions, one for the upper and one for the lower side of the aerofoil. These functions are dependent on time, hence the aerofoil can perform oscillating movement, which is the case when subjected to utter. The governing equations for the ow are the Euler equations. By assuming thin aerofoil, small angle of attack and that the perturbation of the wake is small, the problem is linearised. It is shown that the linearised Euler equations can be rewritten as the Cauchy-Riemann equations, and an analytic function exists where its real part is the horizontal velocity component and its imaginary part is the vertical velocity component with opposite sign. The ow eld is then investigated in the complex plane by making an appropriate branch cut removing all discontinuities, and with restrictions on the analytic function such that the kinematic and boundary conditions are satis ed. By using Cauchy's integral formula an expression for the anti-symmetric part of the analytic function is achieved. A general expression for the velocity jump over the wake is obtained, which is applied to the speci c case of harmonic oscillations for a symmetric aerofoil. In the end three types of utter is investigated; twisting oscillations around the centre of stiness, vertical oscillation, and aileron flutter.
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Hazby, Hamid Richard. "Centrifugal compressor aerodynamics." Thesis, University of Cambridge, 2011. https://www.repository.cam.ac.uk/handle/1810/252228.
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Potts, Jonathan Roger. "Disc-wing aerodynamics." Thesis, University of Manchester, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.569224.
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Disc-wings are a class of un-powered, axi-symmetric flight vehicles that use spin to achieve acceptably stable flight characteristics. Examples of commonly encountered disc-wings include the Frisbee sports disc, the athletics discus and the clay pigeon. Historically, it appears that most disc-wing designs have been based on trial and error approaches. The main aim of the present work is to develop a theory of flight for spinstabilised disc-wings that can be used to inform the process of their design. This theory of flight is based both on theoretical analysis and experimental data. It is shown from a simple trim and stability analysis that a disc-wing with positive camber will trim at a positive angle of attack. However, for most axi-symmetric crosssectional shapes, the aerodynamic centre is ahead of the centre of the disc (which by definition is the disc centre of gravity). Hence, the static margin is negative and the disc is unstable in pitch. In practice, a disc-wing must be spun in order to fly successfully. The imparted angular momentum due to the spin means that, through precessional effects, the destabilising pitching moments tend to result in a rolling motion rather than a pitching motion. Thus, without spin, a disc-wing would tumble soon after release. With spin however, the discwing will not tumble, instead it tends to exhibit a relatively benign roll to the left or right, depending on the spin direction. The aerodynamic characteristics of various disc-wing geometries based around a Frisbee sports disc are investigated through a series of wind tunnel experiments on a spinning and non-spinning disc. It is shown that the basic lift and drag characteristics are consistent with those expected for a finite wing of the same aspect ratio. The pitching moment characteristic is key to understanding the resulting disc dynamics. A comparison of pitching moment curves is given, for a number of different cross-sectional profiles, some tested as part of the present work and some taken from data found in the literature. It is shown that the Frisbee cross-section is unique in that the pitching moment is zero at around 9° angle of attack, approximately coincident with the angle attack for best lift to drag ratio, and that the disc is approximately neutrally stable in this region. It is these characteristics that enable a typical Frisbee to fly successfully. Spin has almost negligible effect on aerodynamic forces and moments. Force and moment data is supported by surface pressure data, and by on and off surface flow visualisation. Surface pressure data shows that the aerodynamic centre of the Frisbee cross-section is shifted aft by the presence of an aft pressure peak that is not present on other cross-section shapes. The aft pressure peak is a function of both the upper surface geometry and the presence of the cavity on the under surface of the disc. Flow visualisation and pressure data are used to propose a model of disc-wing flow topology that is dependant on the angle of attack and includes leading edge separation and reattachment, recirculating cavity flow and a pair of trailing vortices. To understand further disc-wing flight dynamics and the effect of aerodynamic characteristics, a six-degree of freedom disc-wing simulation model was developed using Matlab. The simulation is validated against published Frisbee trajectory data obtained from free-flight experiments. Flight profiles are also discussed for a number of different launch conditions consistent with a range of typical Frisbee throws. The simulation is also used to demonstrate that with control moments from suitable control effectors, it is possible to generate a number of proscribed manoeuvres, including a spiral turn and a spiral roll.
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Standen, Paul. "Towed vehicle aerodynamics." Thesis, University of Bath, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.311175.
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Zamboni, Giulio. "Fan root aerodynamics." Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.611841.
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Baig, Mariam S. "Aerodynamics and Dysphagia." Cleveland State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=csu1375371353.
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Wilks, Brett Landon Burkhalter Johnny Evans. "Aerodynamics of wrap-around fins in supersonic flow." Auburn, Ala., 2005. http://repo.lib.auburn.edu/2005%20Fall/Thesis/WILKS_BRETT_54.pdf.
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Gillam, David A. "Airloads on a finite wing in a time dependent incompressible freestream." Diss., Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/12371.
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Rigaldo, Alexis. "Aerodynamics Gust Response Prediction." Thesis, KTH, Flygdynamik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-41506.
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This project presents the work performed within the aerodynamics department of Airbus Operation SAS inToulouse through a ve months master thesis. This department works with the industrialization and the use of tools developed by laboratories to perform CFD aerodynamic simulations. The primary purpose of the present work was to support the development of gust analysis methods based on CFD. A new gust model has been developed and integrated to the aerodynamic solver elsA.This solver has been used in order to compute the unsteady aerodynamic simulations for both gust loads and forced motions with CFD. The results were then compared with those from a Doublet Lattice Method computation for validation. Once the validation phase was ended with good agreement between the two methods, a Chimera simulation has been carried out.
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Doig, Graham Mechanical & Manufacturing Engineering Faculty of Engineering UNSW. "Compressible ground effect aerodynamics." Awarded by:University of New South Wales. Mechanical & Manufacturing Engineering, 2009. http://handle.unsw.edu.au/1959.4/44696.
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The aerodynamics of bodies in compressible ground effect flowfields from low-subsonic to supersonic Mach numbers have been investigated numerically and experimentally. A study of existing literature indicated that compressible ground effect has been addressed sporadically in various contexts, without being researched in any comprehensive detail. One of the reasons for this is the difficulty involved in performing experiments which accurately simulate the flows in question with regards to ground boundary conditions. To maximise the relevance of the research to appropriate real-world scenarios, multiple bodies were examined within the confines of their own specific flow regimes. These were: an inverted T026 wing in the low-to-medium subsonic regime, a lifting RAE 2822 aerofoil and ONERA M6 wing in the transonic regime, and a NATO military projectile at supersonic Mach numbers. Two primary aims were pursued. Firstly, experimental issues surrounding compressible ground effect flows were addressed. Potential problems were found in the practice of matching incompressible Computational Fluid Dynamics (CFD) simulations to wind tunnel experiments for the inverted wing at low freestream Mach numbers (<0.3), where the inverted wing was found to experience significant compressible effects even at Mach 0.15. The approach of matching full-scale CFD simulations to scale model testing at an identical Reynolds number but higher Mach number was analysed and found to be prone to significant error. An exploration was also conducted of appropriate ways to conduct experimental tests at transonic and supersonic Mach numbers, resulting in the recommendation of a symmetry (image) method as an effective means of approximating a moving ground boundary in a small-scale blowdown wind tunnel. Issues of scale with regards to Reynolds number persisted in the transonic regime, but with careful use of CFD as a complement to experiments, discrepancies were quantified with confidence. The second primary aim was to use CFD to gain a broader understanding of the ways in which density changes in the flowfield affect the aerodynamic performance of the bodies in question, in particular when a shock wave reflects from the ground plane to interact again with the body or its wake. The numerical approach was extensively verified and validated against existing and new experimental data. The lifting aerofoil and wing were investigated over a range of mid-to-high subsonic Mach numbers (1>M???>0.5), ground clearances and angles of incidence. The presence of the ground was found to affect the critical Mach number, and the aerodynamic characteristics of the bodies across all Mach numbers and clearances proved to be highly sensitive to ground proximity, with a step change in any variable often causing a considerable change to the lift, moment and drag coefficients. At the lowest ground clearances in both two and three dimensional studies, the aerodynamic efficiency was generally found to be less than that of unbounded (no ground) flight for shock-dominated flowfields at freestream Mach numbers greater than 0.7. In the fully-supersonic regime, where shocks tend to be steady and oblique, a supersonic spinning NATO projectile travelling at Mach 2.4 was simulated at several ground clearances. The shocks produced by the body reflected from the ground plane and interacted with the far wake, the near wake, and/or the body itself depending on the ground clearance. The influence of these wave reflections on the three-dimensional flowfield, and their resultant effects on the aerodynamic coefficients, was determined. The normal and drag forces acting on the projectile increased in exponential fashion once the reflections impinged on the projectile body again one or more times (at a height/diameter ground clearance h/d<1). The pitching moment of the projectile changed sign as ground clearance was reduced, adding to the complexity of the trajectory which would ensue.
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Murphy, John. "Intake Ground Vortex Aerodynamics." Thesis, Cranfield University, 2008. http://hdl.handle.net/1826/3515.
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When an aircraft is operating in static or near static conditions during taxiing or take-o
a vortex can form between the ground and the intake. With engine diameters increasing,
intakes are moving non-dimensionally closer to the ground and as a consequence
the likelihood of vortex formation during the aircraft operating envelope is set to increase.
To date there is little quantitative knowledge therefore a greater understanding
is required. This research is aimed at providing an extensive quantitative parametric
study of vortex formation leading to advanced design rules for future engines.
A 1/30
th
scale generic model intake was operated in the Cranfield University 8 ′
×
6 ′
wind tunnel to examine ground vortex formation under quiescent, headwind and crosswind
conditions. Stereoscopic Particle Image Velocimetry and total pressure measurements
have been extensively taken to assess the external and internal flowfields. For
the first time experiments with a rolling ground plane have been performed to provide
insight into the formation and characteristics of ground vortices during take-o .
As the velocity ratio reduces a characteristic trend is established whereby the vortex is
initially weak, increases in strength to a local maximum and reduces to zero thereafter.
The operating points that generate the strongest vortex for a given configuration have
been determined and an empirical model has been developed which can predict the vortex
strength and fan face distortion for any configuration. Under headwind conditions
a new vortex formation criterion has been established which also includes contours of
vortex circulation. An a priori prediction of the vortex strength under headwind conditions
has also been developed which considers the approaching and intake induced
vorticity sources, the latter of which is determined empirically. Good agreement is
found between the model and the experimental dataset. The rolling ground plane experiments
demonstrate significant sensitivities illustrating that the correct conditions
must be simulated properly.
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Main, A. D. J. "Annular turbine cascade aerodynamics." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239350.
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Underwood, Lindsey. "Aerodynamics of Track Cycling." Thesis, University of Canterbury. Mechanical Engineering, 2012. http://hdl.handle.net/10092/7804.
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The aim of this thesis was to identify ways in which the velocity of a track cyclist could be increased, primarily through the reduction of aerodynamic drag, and to determine which factors had the most significant impact on athlete performance. An appropriate test method was set up in the wind tunnel at the University of Canterbury to measure the aerodynamic drag of different cycling positions and equipment, including helmets, skinsuits, frames and wheels, in order to measure the impact of specific changes on athlete performance.
A mathematical model of the Individual Pursuit (IP) event was also created to calculate the velocity profile and finishing time for athletes competing under different race conditions. The model was created in Microsoft Excel and used first principles to analyse the forces acting on a cyclist, which lead to the development of equations for power supply and demand. The mathematical model was validated using SRM data for eleven, elite track cyclists, and was found to be accurate to 0.31s (0.16%). An analysis of changes made to the bike, athlete, and environmental conditions using the mathematical model showed that the drag area and air density had the greatest impact on the finishing time. The model was then used to predict the finishing times for different pacing strategies by generating different power profiles for a given athlete with a fixed stock of energy (the work done remained the same for all generated power profiles) in order to identify the optimal pacing strategy for the IP. The length of time spent in the initial acceleration phase was found to have a significant impact on the results, although all strategies simulated with an initial acceleration phase resulted in a faster finishing time than all other strategies simulated.
Results from the wind tunnel tests showed that, in general, changes made to the position of the cyclist had the greatest impact on the aerodynamic drag compared to changes made to the equipment. Multiple changes in position had a greater impact on drag than individual changes in position, but the changes were not additive; the total gain or loss in drag for multiple changes in position was not the sum of individual gains or losses in drag. Actual gains and losses also varied significantly between athletes, primarily due to differences in body size and shape, riding experience, and reference position from which changes were made from. Changes in position that resulted in a reduction of the frontal area, such as lowering the handlebars and head, were the most successful at reducing the aerodynamic drag, and a change in skinsuit was found to have the greatest impact on drag out of all equipment changes, primarily due to the choice of material and seam placement. The mathematical model was used to quantify the impact of changes in position and equipment made in the wind tunnel on the overall finishing time for a given athlete competing in an IP event. Time savings of up to 8 seconds were seen for multiple changes in position, and up to 5 seconds for changes to the equipment.
Overall this thesis highlights the significance of aerodynamics on athlete performance in track cycling, suggesting that it is worthwhile spending time and money on research and technology to find new ways to reduce the aerodynamic drag and maximise the speed of cyclists. Although this thesis primarily concentrates on the Individual Pursuit event in track cycling, the same principles can be applied to other cycling disciplines, as well as to other sports.
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Aishwar, Ravichandran. "Aerodynamics of Bird Flight." Thesis, KTH, Skolan för teknikvetenskap (SCI), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-154492.
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It is the objective of this thesis project to understand the physics behind the different modes of bird flight and to do numerical two dimensional simulations of pure plunging, pure pitching and combined pitch-plunging motion of an aerofoil. First, the different physical models used to understand the generation of thrust are explained. Then the numerical model used for the simulation is explained briefly. Then the results and analysis of the numerical simulations are presented.
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Horikiri, Kana. "Aerodynamics of wind turbines." Thesis, Queen Mary, University of London, 2011. http://qmro.qmul.ac.uk/xmlui/handle/123456789/1881.
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The study of rotor blade aerodynamic performances of wind tur- bine has been presented in this thesis. This study was focused on aero- dynamic effects changed by blade surface distribution as well as grid solution along the airfoil. The details of numerical calculation from Fluent were described to help predict accurate blade performance for comparison and discussion with available data. The direct surface curvature distribution blade design method for two-dimensional airfoil sections for wind turbine rotors have been dis- cussed with the attentions to Euler equation, velocity diagram and the factors which affect wind turbine performance and applied to design a blade geometry close to an existing wind turbine blade, Eppler387, in order to argue that the blade surface drawn by direct surface curvature distribution blade design method contributes aerodynamic efficiency. The FLUENT calculation of NACA63-215V showed that the aero- dynamic characteristics agreed well with the available experimental data at lower angles of attack although it was discontinuities in the surface curvature distributions between 0.7 and 0.8 in x/c. The dis- continuities were so small that the blade performance could not be affected. The design of Eppler 387 blade performed to reduce drag force. The discontinuities of surface distributionmatched the curve of the pressure coefficients. It was found in the curvature distribution that the leading edge pressure side had difficulties to connect to Bezier curve and also the trailing edge circle was never be tangent to the lines of trailing edge pressure and suction sides due to programming difficulties.
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Vafidis, Constantinos. "Aerodynamics of reciprocating engines." Thesis, Imperial College London, 1986. http://hdl.handle.net/10044/1/38177.
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Rojratsirikul, Pinunta. "Aerodynamics of flexible membranes." Thesis, University of Bath, 2010. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.527135.
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Membrane wings are used both in nature and small aircraft as lifting surfaces. For these low Reynolds number applications, separated flows are common and are the main sources of unsteadiness. Adaptability of the membrane wing is known to improve the vehicle performance; and membrane compliancy in animal wings such as bats contributes significantly to their astonishing flights. Yet, the aerodynamic characteristics of the membranes are still largely unknown. An experimental study of flexible membranes at low Reynolds numbers was undertaken. Two-dimensional membrane aerofoils were investigated, with particular focus on the unsteady aspects. Membrane deformation, flow fields and fluid-structure interaction were examined over a range of angles of attack and freestream velocities. A comprehensive study of the effect of membrane pre-strain and excess length was carried out. Low aspect ratio membrane wings were investigated for rectangular and nonslender delta wings. The amplitude and mode of membrane vibration are found to be dependent mainly on the location and the unsteadiness level of the shear layer. The results indicate a strong coupling of unsteady flow with the membrane oscillation. With increasing Reynolds number, the separated shear layer becomes more energetic and closer to the surface. The membrane not only has smaller size of the separation region compared to a rigid aerofoil, but also excites the roll-up of large vortices which might lead to delayed stall. The membrane aerofoils with excess length exhibit higher vibration modes, earlier roll-up and smaller separated region, compared to the ones with pre-strain. This smaller separated region delays the onset of membrane vibrations to a larger incidence. For the low aspect ratio membrane wings, the combination of tip vortices and leading-edge vortex shedding results in a mixture of streamwise and spanwise vibrational modes. The flexibility benefits the rectangular wing more than the delta wing by increasing the maximum normal force and the force slope by a larger amount. Similar to the two-dimensional membrane aerofoils, the Strouhal numbers of the oscillations are on the order of unity, and there is a coupling with the wake instabilities in the post-stall region. Stronger tip vortices on membrane wings contribute significantly to total lift enhancement.
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Nandamudi, Srihimaja. "Aerodynamics of Vocal Vibrato." Bowling Green State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1499427478103556.
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Detwiler, Kevin P. "Reduced fan noise radiation from a supersonic inlet." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-09192009-040457/.
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Job, Štefan. "Experimentální měření aerodynamických silových účinků." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2012. http://www.nusl.cz/ntk/nusl-230273.
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This thesis deals with the effect of the aerodynamic forces on a vehicle. It contains the description of the test run of the vehicle, the proposal on how to process the measurements, the processing of the measurements themselves, and the final assessment of the results as to their accuracy and the possibility of repeating the experiment. Furthermore, this thesis contains the comparison of the effect of the individual aerodynamic features on the race car.
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Saini, Manjinder. "Experimental and computational study of airfoil load alteration using oscillating fence actuator." Laramie, Wyo. : University of Wyoming, 2008. http://proquest.umi.com/pqdweb?did=1663059971&sid=3&Fmt=2&clientId=18949&RQT=309&VName=PQD.
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Pope, Orrin Dean. "Aerodynamic Centers of Arbitrary Airfoils." DigitalCommons@USU, 2017. https://digitalcommons.usu.edu/etd/6890.
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The study of designing stable aircraft has been widespread and ongoing since the early days of Orville and Wilbur Wright and their famous Wright Flyer airplane. All aircraft as they fly through the air are subject to minor changes in the forces acting on them. The field of aircraft stability seeks to understand and predict how aircraft will respond to these changes in forces and to design aircraft such that when these forces change the aircraft remains stable. The mathematical equations used to predict aircraft stability rely on knowledge of the location of the aerodynamic center, the point through which aerodynamic forces act on an aircraft. The aerodynamic center of an aircraft is a function of the aerodynamic centers of each individual wing, and the aerodynamic center of each wing is a function of the aerodynamic centers of the individual airfoils from which the wing is made. The ability to more accurately predict the location of the airfoil aerodynamic center corresponds directly to an increase in the accuracy of aircraft stability calculations.
The Aerolab at Utah State University has develop new analytic mathematical expressions to describe the location of the airfoil aerodynamic center. These new expressions do not suffer from any of the restrictions, or approximations found in traditional methods, and therefore result in more accurate predictions of airfoil aerodynamic centers and by extension, more accurate aircraft stability predictions.
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Grim, Robert. "Aerodynamická optimalizace vysokovýkonného padákového kluzáku." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2016. http://www.nusl.cz/ntk/nusl-241112.
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This thesis is focused on the aerodynamic analysis of the competition paraglider wing. Drags of the particular wing parts are divided into chapters. The aim was to get a grasp of sizes of the individual components drags in relation to the entire assembly. In the first instance, a 2D profile and then the entire configuration of the 3D wing was analyzed. After the evaluation, some power reserves were detected in an airfoil and so the airfoil shape was optimized. After the optimization of the individual components, the CFD calculation was used again. At the end, geometry changes were evaluated.
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Peters, Brett. "On Accelerating Road Vehicle Aerodynamics." Thesis, The University of North Carolina at Charlotte, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10791882.
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Road vehicle aerodynamics are primarily focused on developing and modeling performance at steady-state conditions, although this does not fully encompass the entire operating envelope. Considerable vehicle acceleration and deceleration occurs during operation, either because of driver input or from transient weather phenomenon such as wind gusting. With this considered, high performance road vehicles experience body acceleration rates well beyond ±1G to navigate courses during efficient transition in and out of corners, accelerating from maximum straight-line speed to manageable cornering speeds, and then back to maximum straight-line speed. This dissertation aims to answer if longitudinal acceleration is important for road vehicle aerodynamics with the use of transient Computational Fluid Dynamics (CFD) to develop a method for obtaining ensemble averages of forces and flow field variables. This method was developed on a simplified bluff body, a channel mounted square cylinder, achieving acceleration through periodic forcing of far field velocity conditions. Then, the method was applied to an open-source road vehicle geometry, the DrivAer model, and a high performance model which was created for this dissertation, the DrivAer-GrandTouringRacing (GTR) variant, as a test model that generates considerable downforce with low ground proximity. Each test body experienced drag force variations greater than ±10% at the tested velocities and acceleration rates with considerable variations to flow field distributions. Finally, an empirical formulation was used to obtain non-dimensional coefficients for each body from their simulated force data, allowing for force comparison between geometries and modeling of aerodynamic force response to accelerating vehicle conditions.
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Kontis, Konstantinos. "Projectile aerodynamics : measurement and computation." Thesis, Cranfield University, 1997. http://hdl.handle.net/1826/1678.
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An experimental study has been performed at M∞=8.2 and Re∞/cm=93000 to examine:
1. The effect of strakes on the aerodynamic characteristics and performance on slender elliptic cone missile configurations. Some information regarding the shock layer was obtained from schlieren pictures. Detailed flow properties in the shock layer were obtained, for some elliptic cone configurations with and without strakes, using a threedimensional, high resolution, iterative, finite volume parabolized Navier-Stokes solver. Surface flow visualisation, using an oil-dot technique, and pressure measurements were made on one of the models to determine the effect of strakes. Lift, drag and pitching moment characteristics for the elliptic cones with and without strakes were obtained using a three component strain-gauge balance.
No gross external flow differences were detected from the schlieren pictures for models tested due to the addition of strakes. Oil-dot visualisation demonstrates that the strakes alter the surface flow characteristics and tended to inhibit the cross-flow. The addition of strakes caused a reduction of pressure on the leeward side and an increase of pressure on the windward side. The strakes produced a significant increase in the lift and drag coefficients, in the incidence range of 0° to 200. The right elliptic cone without strakes with its major axis horizontal exhibits higher lift coefficients than the cone with its major axis vertical.
The numerical study predicted the complex flowfield surrounding the right elliptic cone with its major axis horizontal, gave a better understanding of the complicated nature of the flow and good indications of the shock shape and vortex core positions. An estimation model of the aerodynamic forces and moments for the right elliptic cone with and without strakes was developed based on the standard Newtonian theory. The model successfully predicted the experimental trends in the aerodynamic coefficients.
2. The aerodynamic effectiveness of a cylinder flare body at zero incidence under laminar and turbulent boundary layer conditions. Two nose geometries, namely a 10° half-angle sharp cone and a hemisphere, were used. The surface flow over the cylinderflare body was studied using oil-dot and liquid crystal techniques. Some information regarding the shock layer was obtained from schlieren pictures. The effects of entropy layer and boundary layer state on flare effectiveness were deduced from pressure measurements over the cylinder and the flare.
The most important difference between the laminar and turbulent boundary layer interaction is that a much smaller angle is necessary to cause laminar separation than that necessary for turbulent separation. The determination of incipient separation is very sensitive to the detection method employed. The existence of a small scale separation bubble can explain the differences in the determination of incipient separation angles if different experimental methods are used. The addition of a hemisphere nose reduces the surface pressure and heat transfer levels on the flare. This is due to loss of reservoir pressure across the bow shock wave. The reduction of flare pressure also reduces the separated flow lengths for the laminar case, whereas for the turbulent case the separated flow lengths are increased. This may be due to the boundary layer along the cylinder body not being fully developed. The effect of Mach shear on the flare pressures distribution has been calculated theoretically. The model predicted the experimental results satisfactorily.
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Bomphrey, Richard J. "The aerodynamics of insect flight." Thesis, University of Oxford, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.410318.
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Stevenson, J. C. "Traction kite testing and aerodynamics." Thesis, University of Canterbury. Mechanical Engineering, 2003. http://hdl.handle.net/10092/7688.
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A Traction kite is a controllable high performance kite used to pull other objects in a desired direction. In recent years Traction kites have been used for Kite Surfing and Kite Buggying, generating significant sales revenue. In conjunction with Peter Lynn Kites Ltd, this aim of this project was to develop testing methods to determine Traction kite performance. An additional aim was to lay the fundamental groundwork of kite theory to enable further research on kites.
The original testing method used a car-based test rig, in which kites were flown from the roof of the car while driving down a beach. By measuring each kite's line angle and tension under various conditions, the performance of each kite could be determined. Despite extensive development this method was only moderately successful. In particular, the tangent relationship between a kite's line angle and Lift to Drag ratio caused large experimental errors.
In light of the difficulties, a circular testing method was developed for testing Traction kites. It was found that if a kite was flown indoors, in a horizontal circle around the flyer, the performance of the kite was related to the geometry of the test setup. This method was far less sensitive to measurement error and provided very good kite performance results. Unfortunately, this method is limited by the size of the required test site.
Investigations of kite theory determined that the stable flying location of a kite could be predicted and this led to other key flight characteristics. In particular, the structural requirements of a kite can be addressed and the initial turning properties of a kite can be determined.
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Zheng, Yun. "Computational aerodynamics on unstructed meshes." Thesis, Durham University, 2004. http://etheses.dur.ac.uk/2830/.
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New 2D and 3D unstructured-grid based flow solvers have been developed for simulating steady compressible flows for aerodynamic applications. The codes employ the full compressible Euler/Navier-Stokes equations. The Spalart-Al Imaras one equation turbulence model is used to model turbulence effects of flows. The spatial discretisation has been obtained using a cell-centred finite volume scheme on unstructured-grids, consisting of triangles in 2D and of tetrahedral and prismatic elements in 3D. The temporal discretisation has been obtained with an explicit multistage Runge-Kutta scheme. An "inflation" mesh generation technique is introduced to effectively reduce the difficulty in generating highly stretched 2D/3D viscous grids in regions near solid surfaces. The explicit flow method is accelerated by the use of a multigrid method with consideration of the high grid aspect ratio in viscous flow simulations. A solution mesh adaptation technique is incorporated to improve the overall accuracy of the 2D inviscid and viscous flow solutions. The 3D flow solvers are parallelised in a MIMD fashion aimed at a PC cluster system to reduce the computing time for aerodynamic applications. The numerical methods are first applied to several 2D inviscid flow cases, including subsonic flow in a bump channel, transonic flow around a NACA0012 airfoil and transonic flow around the RAE 2822 airfoil to validate the numerical algorithms. The rest of the 2D case studies concentrate on viscous flow simulations including laminar/turbulent flow over a flat plate, transonic turbulent flow over the RAE 2822 airfoil, and low speed turbulent flows in a turbine cascade with massive separations. The results are compared to experimental data to assess the accuracy of the method. The over resolved problem with mesh adaptation on viscous flow simulations is addressed with a two phase mesh reconstruction procedure. The solution convergence rate with the aspect ratio adaptive multigrid method and the direct connectivity based multigrid is assessed in several viscous turbulent flow simulations. Several 3D test cases are presented to validate the numerical algorithms for solving Euler/Navier-Stokes equations. Inviscid flow around the M6 wing airfoil is simulated on the tetrahedron based 3D flow solver with an upwind scheme and spatial second order finite volume method. The efficiency of the multigrid for inviscid flow simulations is examined. The efficiency of the parallelised 3D flow solver and the PC cluster system is assessed with simulations of the same case with different partitioning schemes. The present parallelised 3D flow solvers on the PC cluster system show satisfactory parallel computing performance. Turbulent flows over a flat plate are simulated with the tetrahedron based and prismatic based flow solver to validate the viscous term treatment. Next, simulation of turbulent flow over the M6 wing is carried out with the parallelised 3D flow solvers to demonstrate the overall accuracy of the algorithms and the efficiency of the multigrid method. The results show very good agreement with experimental data. A highly stretched and well-formed computational grid near the solid wall and wake regions is generated with the "inflation" method. The aspect ratio adaptive multigrid displayed a good acceleration rate. Finally, low speed flow around the NREL Phase 11 Wind turbine is simulated and the results are compared to the experimental data.
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Barber, Sarah. "The aerodynamics of Association Footballs." Thesis, University of Sheffield, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.443860.
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McClain, A. "Aerodynamics of nonslender delta wings." Thesis, University of Bath, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.401655.
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Maybury, Will J. "The aerodynamics of bird bodies." Thesis, University of Bristol, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340357.
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Demargne, Albert André Jean. "Aerodynamics of stator-shroud leakage." Thesis, University of Cambridge, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.620983.
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Walker, Simon M. "Insect flight : kinematics and aerodynamics." Thesis, University of Oxford, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.670125.
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Van, Der Kindere Jacques. "Aerodynamics of surface-mounted ribs." Thesis, University of Southampton, 2017. https://eprints.soton.ac.uk/416112/.
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The flow over ribs consists of a forward-facing step followed by a backward-facing step. The interaction between the aerodynamics of these two canonical obstacles leads to complex patterns in an oscillating flow which depend on rib length. In order to study the aerodynamics of ribs, four steps were taken which involve multiple forms of velocity and pressure measurements. To begin, a method to estimate pressure fields from particle image velocimetry is applied and validated against pressure measurements. This provides pressure information necessary for the rest of the study. Second, the characteristics of the flow over ribs of varying length are studied in a statistical sense. Trends identified in previous work were found and extended to new quantities. The effect of free-stream turbulence on the characteristics of the flow is studied. It highlights the sensitivity of separation over short obstacles to free-stream turbulence in contrast with the unchanging separation over longer obstacles. Finally, the relationship between pressure and velocity is described using modelling of velocity components from surface pressure information. It shows that individual patterns in velocity fluctuations such as vortex shedding and shear layer flapping are closely linked to surface pressure fluctuations.
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Knapke, Clint J. "Aerodynamics of Fan Blade Blending." Wright State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=wright1567517259599736.
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Morren, Sybil Huang. "Transonic aerodynamics of dense gases." Thesis, Virginia Tech, 1990. http://hdl.handle.net/10919/42210.
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Transonic flow of dense gases for two-dimensional, steady state, flow over a NACA 0012 airfoil was predicted analytically. The computer code used to model the dense gas behavior was a modified version of Jameson's FLOS2 airfoil code. The modifications to the code enabled modeling the dense gas behavior near the saturated vapor curve and critical pressure region where the fundamental derivative, Γ, is negative. This negative Γ region is of interest because the nonclassical gas behavior such as formation and propagation of expansion shocks, and the disintegration of inadmissible compression shocks. The results of this study indicated that dense gases with undisturbed thermodynamic states in the negative Γ region show a significant reduction in the extent of the transonic regime as compared to that predicted by the perfect gas theory. The results of the thesis support existing theories and predictions of the nonclassical, dense gas behavior from previous investigations.Master of Science
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Desenfans, Philip. "Aerodynamics of the Maple Seed." Aircraft Design and Systems Group (AERO), Department of Automotive and Aeronautical Engineering, Hamburg University of Applied Sciences, 2019. http://d-nb.info/1204982848.
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Purpose - The paper presents a theoretical framework that describes the aerodynamics of a falling maple (Acer pseudoplatanus) seed. --- Methodology - A semi-empirical method is developed that provides a ratio stating how much longer a seed falls in air compared to freefall. The generated lift is calculated by evaluating the integral of two-dimensional airfoil elements using a preliminary falling speed. This allows for the calculation of the definitive falling speed using Blade Element Momentum Theory (BEMT); hereafter, the fall duration in air and in freefall are obtained. Furthermore, the input-variables of the calculation of lift are transformed to require only the length and width of the maple seed. Lastly, the method is applied to two calculation examples as a means of validation. --- Findings - The two example calculations gave percentual errors of 5.5% and 3.7% for the falling speed when compared to measured values. The averaged result is that a maple seed falls 9.9 times longer in air when released from 20 m; however, this result is highly dependent on geometrical parameters which can be accounted for using the constructed method. --- Research limitations - Firstly, the coefficient of lift is unknown for the shape of a maple seed. Secondly, the approximated transient state is yet to be verified by measurement. --- Originality / Value - The added value of this report lies in the reduction of simplifications compared to BEMT approaches. In this way a large amount of accuracy is achieved due to the inclusion of many geometrical parameters, even though simplicity is maintained. This has been accomplished through constructing a simple three-step method that is fundamental and essentially non-iterative.
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Vardaki, Eleni. "Aerodynamics of nonslender delta wings." Thesis, University of Bath, 2006. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.438644.
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Srinivasa, Murthy P. "Low Reynolds Number Airfoil Aerodynamics." Thesis, Indian Institute of Science, 2000. https://etd.iisc.ac.in/handle/2005/229.
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In this thesis we describe the development of Reynolds- averaged Navier Stokes code for the flow past two- dimensional configuration. Particularly, emphasis has been laid on the study of low Reynolds number airfoil aerodynamics.
The thesis consists of five chapters covering the back ground history, problem formulation, method of solution and discussion of the results and conclusion.
Chapter I deals with a detailed background history of low Reynolds number aerodynamics, problem associated with it, state of the art, its importance in practical applications in aircraft industries.
Chapter II describes the mathematical model of the flow physics and various levels of approximations. Also it gives an account of complexity of the equations at low Reynolds number regarding flow separation, transition and reattachment.
Chapter III describes method of solution, numerical algorithm developed, description of various upwind schemes, grid system, finite volume discrieti-zation of the governing equations described in Chapter II.
Chapter IV describes the application of the newly developed Navier Stokes code for the test cases from GAMM Workshop proceedings. Also it describes validation of the code for Euler solutions, Blasius solution for the flow past flat plate and compressible Navier Stokes solution for the flow past NACA 0012 Airfoil at low Reynolds number.
Chapter V describes the application of the Navier Stokes code for the more test cases of current practical interest . In this chapter laminar separation bubble characteristics are investigated in detail regarding formation, growth and shedding in an unsteady environment.
Finally the conclusion is drawn regarding the robustness of the newly developed code in predicting the airfoil aerodynamic characteristics at low Reynolds number both in steady and unsteady environment.
Lastly, suggestion for future work has been highlighted.
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Srinivasa, Murthy P. "Low Reynolds Number Airfoil Aerodynamics." Thesis, Indian Institute of Science, 2000. http://hdl.handle.net/2005/229.
Full textAbstract:
In this thesis we describe the development of Reynolds- averaged Navier Stokes code for the flow past two- dimensional configuration. Particularly, emphasis has been laid on the study of low Reynolds number airfoil aerodynamics.
The thesis consists of five chapters covering the back ground history, problem formulation, method of solution and discussion of the results and conclusion.
Chapter I deals with a detailed background history of low Reynolds number aerodynamics, problem associated with it, state of the art, its importance in practical applications in aircraft industries.
Chapter II describes the mathematical model of the flow physics and various levels of approximations. Also it gives an account of complexity of the equations at low Reynolds number regarding flow separation, transition and reattachment.
Chapter III describes method of solution, numerical algorithm developed, description of various upwind schemes, grid system, finite volume discrieti-zation of the governing equations described in Chapter II.
Chapter IV describes the application of the newly developed Navier Stokes code for the test cases from GAMM Workshop proceedings. Also it describes validation of the code for Euler solutions, Blasius solution for the flow past flat plate and compressible Navier Stokes solution for the flow past NACA 0012 Airfoil at low Reynolds number.
Chapter V describes the application of the Navier Stokes code for the more test cases of current practical interest . In this chapter laminar separation bubble characteristics are investigated in detail regarding formation, growth and shedding in an unsteady environment.
Finally the conclusion is drawn regarding the robustness of the newly developed code in predicting the airfoil aerodynamic characteristics at low Reynolds number both in steady and unsteady environment.
Lastly, suggestion for future work has been highlighted.
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Pande, Abhijit. "Effect of struts on aeroacoustics of axisymmetric supersonic inlets." Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-07292009-090449/.
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Stiborová, Dana. "Aktivní aerodynamické prvky osobních vozidel." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2017. http://www.nusl.cz/ntk/nusl-318777.
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In this diploma thesis active aerodynamic components are designed, specifically brake cooling duct and active automotive wing. Cooling duct prototype and also active regulation controlling electronics including the software were created. Road test was performed to measure the duct parameters. Construction design and the active regulation function of the automotive wing were created. The influence of the wing on aerodynamic characteristics of the car was determined.
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Xin, Hong. "Development and validation of a generalized ground effect model for lifting rotors." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/11880.
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Yoo, Kyung M. "Unsteady vortex lattice aerodynamics for rotor aeroelasticity in hover and in forward flight." Diss., Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/11961.
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Lal, Mihir Kumar. "Unsteady pressure and inflow velocity on a pitching rotor blade in hover." Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/12053.
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