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.

Several types of discrepancies have been examined between CFD simulations, wind tunnel measurements and real world conditions. The results of different wheel rotation methods show that while stationary approaches can often substitute real unsteady wheel rotation, they can also be very sensitive to the exact angular positioning of wheel rims. Using both measured and computed flow fields, the lower part of wheel wake was identified as a key area, showing differences between rotation methods and sources of simulation errors in general. It was also shown that the level of detail in tyre geometry and its deformation near contact patch do not have a large impact on accuracy. Due to the absence of tyre rotation, the tyre sidewall was identified as an important place of flow separation with large effect on flow field and forces. Angle of attack study confirmed that assessing purely straight-line drag causes its under prediction compared to real-world values. This judgement would however benefit from obtaining data in more adverse conditions compared to those currently available. Finally, tyre radial expansion was investigated, causing a drop in drag with increasing vehicle velocity and altering the flow around the rear bodywork. Ignoring this effect can therefore negatively influence the aerodynamic development of a vehicle.

This paper will investigate the development of a landing footprint for a re-entry vehicle. Vehicles can re-enter the atmosphere with a range of orientations, velocities and flight path angles. The central question is whether a vehicle with any combination of these states can be brought to an acceptable landing condition at a particular landing site and with a particular landing speed. To aide in this investigation several models must be implemented, including that of the atmosphere, the vehicles, the Earth, and the aerodynamics. A detailed analysis of the aerodynamic model will be treated, and the equations of motion subject to these aerodynamic laws will then be compared to results from existing atmospheric reentry software. The principles of optimization will then be employed to generate the footprint of landable states, based on maximum and minimum possible downrange distances, for two vehicle concepts.

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No description available.

No description available.

The primary purpose of this study is to perform accurate dynamic measurements on a scaled roller rig designed and constructed by Virginia Tech and the Federal Railroad Administration (VT-FRA Roller Rig). The study also aims at determining the effect of naturally generated third-body layer deposits (because of the wear of the wheel and/or roller) on creep or traction forces. The wheel-rail contact forces, also referred to as traction forces, are critical for all aspects of rail dynamics. These forces are quite complex and they have been the subject of several decades of research, both in experiments and modeling. The primary intent of the VT-FRA Roller Rig is to provide an experimental environment for more accurate testing and evaluation of some of the models currently in existence, as well as evaluate new hypothesis and theories that cannot be verified on other roller rigs available worldwide. The Rig consists of a wheel and roller in a vertical configuration that allows for closely replicating the boundary conditions of railroad wheel-rail contact via actively controlling all the wheel-rail interface degrees of freedom: angle of attack, cant angle, normal load and lateral displacement, including flanging. The Rig has two sophisticated independent drivelines to precisely control the rotational speed of the wheels, and therefore their relative slip or creepage. The Rig benefits from a novel force measurement system, suitable for steel on steel contact, to precisely measure the contact forces and moments at the wheel-rail contact. Experimental studies are conducted on the VT ��" FRA Roller Rig that involved varying the angle of attack, wheel and rail surface lubricity condition (i.e., wet vs. dry rail), and wheel wear, to study their effect on wheel-rail contact mechanics and dynamics. The wheel-rail contact is in between a one-fourth scale AAR-1B locomotive wheel and a roller machined to US-136 rail profile. A quantitative assessment of the creep-creepage measurements, which is an important metric to evaluate the wheel-rail contact mechanics and dynamics, is presented. A MATLAB routine is developed to generate the creep-creepage curves from measurements conducted as part of a broad experimental study. The shape of the contact patch and its pressure distribution have been discussed. An attempt is made to apply the results to full-scale wheels and flat rails. The research results will help in the development of better simulation models for non-Hertzian contact and non-linear creep theories for wheel-rail contact problems that require further research to more accurately represent the wheel-rail interaction. / MS / Rail vehicles are supported, steered, accelerated, and decelerated by contact forces acting in extremely small wheel-rail contact areas. The behavior of these forces is quite complex and a broad interdisciplinary research is needed to understand and optimize the contact mechanics and dynamics problem. Key industry issues, such as control of Rolling Contact Fatigue (RCF), maximizing wheelset mileages, and minimizing the impact of rolling stock on the infrastructure, are directly related to the interaction at the wheel-rail contact. The Rig consists of a wheel and roller in a vertical configuration that allows for closely replicating the boundary conditions of railroad wheel-rail contact via actively controlling all the wheel-rail interface degrees of freedom: angle of attack, cant angle, normal load and lateral displacement, including flanging. The Rig has two sophisticated independent drivelines to precisely control the rotational speed of the wheels, and therefore their relative slip or creepage. The Rig benefits from a novel force measurement system, suitable for steel on steel contact, to precisely measure the contact forces and moments at the wheel-rail contact. The primary purpose of this study is to perform accurate dynamic measurements on a scaled roller rig designed and constructed by Virginia Tech and the Federal Railroad Administration (VT-FRA Roller Rig). Experimental studies are conducted on the VT – FRA Roller Rig that involved varying the angle of attack, the wheel and rail surface lubricity condition (i.e., wet vs. dry rail), and the wheel wear to study their effects on wheel-rail contact mechanics and dynamics. The wheel-rail contact is in between a one-fourth scale AAR-1B locomotive wheel and a roller machined to US-136 rail profile. A quantitative assessment of the creep-creepage measurements, which is an important metric to evaluate the wheel-rail contact mechanics and dynamics, is presented. A MATLAB routine is developed to generate the creep-creepage curves from measurements conducted as part of a broad experimental study. The shape of the contact patch and its pressure distribution have been discussed. An attempt is made to apply the results to full-scale wheels and flat rails. The research results will help in the development of better simulation models for non-Hertzian contact and non-linear creep theories for wheel-rail contact problems that require further research to more accurately represent the wheel-rail interaction.

ITC/USA 2006 Conference Proceedings / The Forty-Second Annual International Telemetering Conference and Technical Exhibition / October 23-26, 2006 / Town and Country Resort & Convention Center, San Diego, California / Telemetry data are usually collected for analysis at some later time and can be monitored to follow the progress of a test. In the case of an Air Data System the signals from the sensors are sent to a computer that calculates the air data parameters for use on multiple LabView-generated displays, as well as to the Data Acquisition System. The readouts on the multiple displays need to be real-time so they are useful to the flight crew. Equations that control the different air data values are determined by what telemetry data are available and the preference of those doing the test planning. These systems need to display the information in a format useful to the flight crew and be reliable.

Baigiamajame magistro darbe nagrinėjamos būsimo eksperimentinio akrobatinio lėktuvo aerodinaminės savybės. Pristatomos tokio pobūdžio sritys (temos), kaip tinkamo sparno profilio parinkimas orlaiviui, reikalingo sparno formos apibrėžimas, sparno būsimos charakteristikos ir parametrų apskaičiavimas, kitų orlaivio dalių ir jų įtakos visai lėktuvo dinamikai analizavimas. Kadangi analizuojamas dvivietis eksperimentinis akrobatinis lėktuvas, tikintis geresnių rodiklių, pasirinktas palyginimo objektas  dvivietis akrobatinis mokomasis lėktuvas SU 29. Remiantis šio lėktuvo esamomis charakteristikomis ir parametrais, pateikiamos išvados ir siūlymai. / The thesis examines the aerodynamics of future experimental aerobatic aircraft. Featured in such areas (topics): proper selection of an aircraft wing profile, the required form of the wing, the wing's future performance and parameter estimation, other aircraft parts and their impact on the entire plane dynamics analysis. As analyzed double seated, experimental aerobatic plane in the hope of better indicators selected comparison object  double seated acrobatic training plane SU 29. Based on the existing aircraft characteristics and parameters, the conclusions and recommendations will be made.

Thesis (M.S.)--Air Force Institute of Technology, 2008. / Title from title page of PDF document (viewed on: Dec 10, 2009).