This thesis describes the development and assessment of an undergraduate wind tunnel test engineering course utilizing the 7ft by 10ft Oran W. Nicks Low Speed Wind Tunnel (LSWT). Only 5 other universities in the United States have a wind tunnel of similar size and none have an undergraduate wind tunnel test engineering course built around it. Many universities use smaller wind tunnels for laboratory instruction, but these experiments are meant to only demonstrate basic concepts. Students go beyond conceptual learning in this wind tunnel test engineering course and conduct real-world experiments in the LSWT. This course puts knowledge into practice and further prepares students whether continuing on to graduate school or industry. Course content mainly originates from the chapters in Low Speed Wind Tunnel Testing by Barlow, Rae, and Pope. This is the most comprehensive book that addresses the specific requirements of large scale, low speed wind tunnel testing. It is not a textbook for novices. The three experiments used in the course are modeled on actual experiments that were performed at the LSWT. They are exactly what a commercial entity would want performed although the time scale is drastically reduced because of class requirements. Students complete the course with a working knowledge of the requirements of large scale, low speed wind tunnel tests because they have successfully performed real-world tests and have performed data reduction that is needed for high-quality industrial tests.

Thesis (Ph. D.)--University of Hong Kong, 2009. / Includes bibliographical references (p. 219-225). Also available in print.

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The velocity profile shape and boundary layer thickness of an equilibrium boundary layer grown over a long fetch of roughness are closely matched with those of a boundary layer artificially thickened using spires (by adjusting the shape and height of the spires). Other turbulent characteristics of these two wind tunnel simula tions of the atmospheric wind are then compared. At the same time, more information on rough wall boundary layers is obtained to allow for a rational choice of the shape and spacing of roughness elements required to produce a particular simulation of the full scale boundary layer. A technique for calculating the shape of boundary layers in exact equilibrium with the roughness beneath, using a data correlation for the wall stress associated with very rough boundaries and a semi-empirical calculation method, is examined experimentally. Wall shear stress, measured directly from a drag plate, i combined with boundary layer integral properties to show that the shear stress formula is reasonably accurate and that the boundary layer grown over a long fetch of roughness is close to equilibrium after passing over a streamwise distance equal to about 350 times the roughness element height. The boundary layer quickly generated using spires proved to be a fair approximation to that grown over a long fetch of roughness, but did not accurately represent the longitudinal turbulence intensity of the full scale atmospheric wind or the naturally grown boundary layer. The boundary layer produced here by spires showed little change in gross characteristics after travelling about eight spire heights downstream of the spires. A distance of six or seven such heights has been advised by other workers in the past. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

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 Marchman / Master of Science

The acoustic treatment and calibration of a new anechoic system for the Virginia Tech Stability Wind Tunnel has been performed. This novel design utilizes Kevlar cloth to provide a stable flow boundary, which eliminates the need for a free jet and jet catcher. To test this concept a series of measurements were performed both to validate the reduction in overall test section noise levels and to ascertain the effect of these modifications on the test section aerodynamics. An extensive program of experiments has been conducted to examine the performance of this new hardware under a range of conditions. These include baseline experiments that reveal the aerodynamic and aeroacoustic performance of the tunnel in its original configuration, treatment of the tunnel circuit with validation of in-flow noise reduction, wind tunnel tests to examine the effect of the test section acoustic treatment, and measurements of the aerodynamic and aeroacoustic characteristics of a NACA 0012 airfoil model over a range of angles of attack and Reynolds numbers. These measurements show that acoustically treating the walls of the circuit both upstream and downstream of the test section, as well as the fan, result in an overall reduction of 5 dB depending on frequency, of the in-flow noise level. These measurements also show that the complete system provides a reduction of between 15 to 20dB depending on frequency, in the in-flow background noise level. Measurements taken both within the test section and in the adjacent chambers also show that large Kevlar windows can be used to quietly and stably contain the flow, eliminating the need for an open-jet and jet catcher system, as well as overall noise levels competitive with many other facilities. Measurements on several airfoils at various angles of attack and Reynolds number show that the interference correction for the fully anechoic configuration is approximately -22% for model with a chord length equal to half the test section height. Aerodynamic measurements with the NACA 0012 airfoil show its lift, drag and boundary layer characteristics at high Reynolds numbers are consistent with theoretical expectations. Measurements of the window deflection as well as examination of flow transpiration through the Kevlar windows were accomplished, both with and without the NACA 0012 model. These measurements, along with the interference correction data, confirm that the Kevlar windows are a stable flow boundary. / Master of Science

As technology for manufacturing small scale prototypes of aeroplanes has become cheaper and more easily viable, the process of Rapid Prototyping has become more common. Rapid Prototyping allows for the fundamental aerodynamic qualities of a geometric body to be tested in a wind tunnel using a small scale prototype. This means smaller prototypes of aircraft can be manufactured more rapidly and at a lower cost, allowing for more extensive testing of a design’s final aerodynamic qualities before any actual full-size production. In order to gain a better insight in the behaviours of the full-sized aircraft itself, a downscaled version of the KTH project UAV ALPHA has been deigned for testing in a low speed wind tunnel. The design will be used in further testing to help confirm simulations and estimations done on the ALPHA of its aerodynamic performance.

<p dir="ltr">Force and moment measurements are valuable tools for evaluating designs in a wind tunnel environment. In fact, this type of research has been conducted ever since the earliest wind tunnels were in use. Load measurement techniques are complicated by hypersonic wind tunnel designs, which often have much shorter test times due to the immense stagnation pressures that are used. Previous research had been conducted once before in the Boeing/AFOSR Mach 6 Quiet Tunnel (BAM6QT) at Purdue University using a six-component moment balance. This initial testing utilized a balance with maximum load limits which far exceeded the loads experienced within the BAM6QT. Because of this, much of the data collected was imprecise. </p><p dir="ltr">Testing was conducted in the BAM6QT using three different balances - a five-component foil, five-component semiconductor, and six-component semiconductor balance. Data were taken for a variety of geometry configurations over a range of total pressures. All data were taken at 0 degree angle of attack. The two geometries used most commonly were the 1 inch diameter blunt nose-tip, 7 degree half-angle, 1.75 inch base diameter cone, with either a 20 degree or 30 degree curved ramp. An additional sharp nose-tip configuration was also used. Results for multiple load components were calculated during each run and compared between each balance type. Results were compared to the surface panel method results of CBAERO, which uses either modified Newtonian theory or the tangent cone method to compute loads. </p><p dir="ltr">Results between each balance type were similar and generally in good agreement. The semiconductor balance designs showed considerably less noise than the foil design. Results of CBAERO matched well with the balance data, with a baseline comparison of the plain blunt cone showing a maximum difference of 12% for the modified Newtonian theory. The more complicated ramp geometries, which exhibited regions of flow detachment, agreed surprisingly well with CBAERO results, despite the more complicated flow phenomena, which was unexpected. The best agreement was generally seen in the cases where the large 30 degree ramp was used, while the sharp nose-tip configuration produced the worst agreement. Overall, CBAERO proved valuable as an approximate method for determining the general magnitude of loads. The sting, used to mount the model in the wind tunnel, was found to drive the oscillation frequency of the model-sting system. The longer sting and less stiff balance used on the six-component system likely contributed to lower oscillation frequencies which affected the results for the pitching moment and normal force. The relationship between startup and running loads was also investigated and a startup-to-running load ratio of 5 to 20 was determined, depending on the load component and geometry.</p>

Research focused on the reduction of uncertainties when considering the wind resource in the vicinity of forestry. This thesis examined the use of high density laser scanning technology to capture the structure of forest canopies along with the measurement of thermal effects using sonic anemometry. Methodologies were then developed to include these high quality data in Computational Fluid Dynamics software in order to allow the complex nature of forestry flows to be considered analytically.

published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy