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.

Dentre as competições nas quais estudantes são desafiados a construir protótipos com finalidades específicas, está a de fazer um veículo que transporte uma pessoa e percorrera a maior distância com um litro de combustível. Um dos fatores que contribuem para o consumo é a resistência aerodinâmica, assim prever seus efeitos é essencial para um bom projeto. Nesse contexto o presente trabalho teve por objetivo avaliar de forma numérica e experimental o escoamento ao redor de um veículo de milhagem e calcular os coeficientes aerodinâmicos de arrasto e sustentação dessas duas formas. Também foi estudada a sensibilidade desses coeficientes ao número de Reynolds e, no caso do teste virtual, aos modelos de turbulência. Através dos resultados de simulações verificou-se que a porção frontal do veículo é a maior responsável pelo arrasto e pela sustentação negativa. Os coeficientes de arrasto caíram com o aumento do número de Reynolds tanto nos ensaios virtuais quanto nos experimentais. Na comparação entre os modelos de turbulência, k-E e k-w em suas formas padrão foram os que mais destoaram em relação aos outros apresentando valores de CD maiores. Os resultados experimentais apresentaram a mesma tendência dos numéricos, e ficaram mais próximos do k- padrão, mas acredita-se que um ângulo de ataque negativo do modelo devido à montagem tenha provocado um aumento no CD obtido experimentalmente. Os valores dos coeficientes de sustentação baixaram com o número de Reynolds nos testes numéricos e aumentaram nos ensaios experimentais. Nas simulações observou-se que a alta velocidade entre as rodas dianteiras devido à pequena distância entre o veículo e o piso era responsável por boa parte da sustentação negativa. Por questões de montagem não foi possível repetir esse efeito solo de forma similar nos experimentos. Os resultados numéricos de visualização do escoamento apresentaram boa concordância com os experimentais. / Among the many competitions in which students are challenged to build up prototypes with specific purposes there, is one in which the goal is to design a car to carry one person and make it go as long as it can with one liter of fuel. One of the factors that contribute for fuel consumption is the aerodynamic resistance, so to predict its effects is essential for a good design. In this context, the present work had as goals the numerical and experimental evaluation of flow around a Supermileage vehicle and to calculate its drag and lift coefficients in these both ways. It was also studied the sensitivity of these forces to Reynolds number and, in the virtual case, to turbulence models. Thanks to simulation results it was verified that the front part of the model is responsible for great part of drag and negative lift. The drag coefficients fell with the increase of Reynolds number in both numerical and experimental tests. In a comparison of turbulence models comparison, k-E and k-w in their standard forms presented higher CD values than the other models. Experimental CD results showed the same tendency of numerical ones, and were closer to standard k-, although it was believed that a negative angle of attack due to experimental assembly issues has made for a higher experimental CD. Lift coefficients values fell with the increase of Reynolds number in virtual analysis and grew in experimental tests. In the simulations it was observed that the high velocity between the two front wheels, due to the short distance between the vehicle and the ground, is responsible for a large portion of the negative lift. Owing to assembly issues it was not possible to reproduce this ground effect on experimental tests. Flow visualization results presented good agreement between experimental and numerical testing.

Dentre as competições nas quais estudantes são desafiados a construir protótipos com finalidades específicas, está a de fazer um veículo que transporte uma pessoa e percorrera a maior distância com um litro de combustível. Um dos fatores que contribuem para o consumo é a resistência aerodinâmica, assim prever seus efeitos é essencial para um bom projeto. Nesse contexto o presente trabalho teve por objetivo avaliar de forma numérica e experimental o escoamento ao redor de um veículo de milhagem e calcular os coeficientes aerodinâmicos de arrasto e sustentação dessas duas formas. Também foi estudada a sensibilidade desses coeficientes ao número de Reynolds e, no caso do teste virtual, aos modelos de turbulência. Através dos resultados de simulações verificou-se que a porção frontal do veículo é a maior responsável pelo arrasto e pela sustentação negativa. Os coeficientes de arrasto caíram com o aumento do número de Reynolds tanto nos ensaios virtuais quanto nos experimentais. Na comparação entre os modelos de turbulência, k-E e k-w em suas formas padrão foram os que mais destoaram em relação aos outros apresentando valores de CD maiores. Os resultados experimentais apresentaram a mesma tendência dos numéricos, e ficaram mais próximos do k- padrão, mas acredita-se que um ângulo de ataque negativo do modelo devido à montagem tenha provocado um aumento no CD obtido experimentalmente. Os valores dos coeficientes de sustentação baixaram com o número de Reynolds nos testes numéricos e aumentaram nos ensaios experimentais. Nas simulações observou-se que a alta velocidade entre as rodas dianteiras devido à pequena distância entre o veículo e o piso era responsável por boa parte da sustentação negativa. Por questões de montagem não foi possível repetir esse efeito solo de forma similar nos experimentos. Os resultados numéricos de visualização do escoamento apresentaram boa concordância com os experimentais. / Among the many competitions in which students are challenged to build up prototypes with specific purposes there, is one in which the goal is to design a car to carry one person and make it go as long as it can with one liter of fuel. One of the factors that contribute for fuel consumption is the aerodynamic resistance, so to predict its effects is essential for a good design. In this context, the present work had as goals the numerical and experimental evaluation of flow around a Supermileage vehicle and to calculate its drag and lift coefficients in these both ways. It was also studied the sensitivity of these forces to Reynolds number and, in the virtual case, to turbulence models. Thanks to simulation results it was verified that the front part of the model is responsible for great part of drag and negative lift. The drag coefficients fell with the increase of Reynolds number in both numerical and experimental tests. In a comparison of turbulence models comparison, k-E and k-w in their standard forms presented higher CD values than the other models. Experimental CD results showed the same tendency of numerical ones, and were closer to standard k-, although it was believed that a negative angle of attack due to experimental assembly issues has made for a higher experimental CD. Lift coefficients values fell with the increase of Reynolds number in virtual analysis and grew in experimental tests. In the simulations it was observed that the high velocity between the two front wheels, due to the short distance between the vehicle and the ground, is responsible for a large portion of the negative lift. Owing to assembly issues it was not possible to reproduce this ground effect on experimental tests. Flow visualization results presented good agreement between experimental and numerical testing.

The atomization problem of high speed viscous jets has many applications in industrial processes and machines. In all these applications, it is required that the droplets have high surface area/volume ratio meaning that the droplets should be as small as possible. This can be achieved with high rates of turbulence and mixing of the flow. In order to constitute a foresight of geometry eects on droplet size, experimental investigation and the determination of flow characteristics in near and far fields of a low-speed air jet have been performed. In order to fulfill this task, three components of instantaneous velocity are measured, using a triple sensor Constant Temperature Anemometer (CTA) system. Through these measurements, mean velocity, Reynolds stress, velocity decay, spreading rate, turbulent kinetic energy, vorticity, and mass entrainment rate values are obtained. Stress-Strain relationship is also observed. Measurements are obtained for a baseline circular nozzle (round jet) as well as for an equilateral triangular and a square nozzle. On the basis of these measurements, the equilateral triangular jet is found to be the best option in order to get highest turbulence and mixing level with smallest core length.

No description available.

<p dir="ltr">The dynamics and characteristics of a high-speed compressible turbulent boundary layer or shear layer have significant effects on separation, heating, shockwave boundary layer interactions, effectiveness of control surfaces, and ultimately the performance of supersonic / hypersonic vehicles. Experimental data with high spatiotemporal resolution and low uncertainty is necessary for understanding complex flow physics and validating computational models. </p><p dir="ltr">Background oriented schlieren (BOS) is a technique derived from traditional schlieren imaging to provide whole-field, quantitative density gradient measurements with a simplistic setup at the expense of reduced spatial resolution and increased uncertainty. The majority of BOS applications focus on low-speed flows with an entocentric optical setup which causes low depth-of-field, wall-blurring, and perspective error issues, making conventional BOS not suitable for high-speed compressible turbulent flow settings. Additionally, despite the widespread adoption of BOS, it has primarily been used as an alternative visualization technique to traditional schlieren imaging and thus the quantitative capabilities of BOS are left under-exploited.</p><p dir="ltr">The workflow of BOS consists of image acquisition, displacement estimation, and integration of the density gradient field. The work presented in this thesis improves the image acquisition and displacement estimation of the BOS workflow by implementing a telecentric optical system and conducting a comprehensive comparison and optimization of several state-of-the-art displacement estimation techniques. Experimental results for a Mach 2 turbulent boundary layer exhibit high spatiotemporal resolution and low uncertainties and are compared against high-fidelity computational results for validation. This work also focuses on the development of BOS velocimetry capabilities, by leveraging ray tracing simulations of an LES turbulent shear layer. Overall this dissertation advances the accuracy, precision, spatial resolution, and capabilities of BOS for fluid dynamic applications relevant to defense and propulsion.</p>

<div>Many important measurements of low-amplitude instabilities related to hypersonic laminar-turbulent boundary-layer transition have been successfully performed with 1-MHz PCB132 pressure sensors. However, there is large uncertainty in measurements made with PCB132 sensors due to their poorly understood response at high frequency. The current work continues efforts to better characterize the PCB132 sensor with a low-pressure shock tube, using the pressure change across the incident shock as an approximate step input. </div><div> </div><div> New vacuum-control valves provide precise control of pre-run pressures in the shock tube, generally to within 1\% of the desired pressure. Measurements of the static-pressure step across the shock made with Kulite sensors showed high consistency for similar pre-run pressures. Skewing of the incident shock was measured by PCB132 sensors, and was found to be negligible across a range of pressure ratios and static-pressure steps. Incident-shock speed decreases along the shock tube, as expected. Vibrational effects on the PCB132 sensor response are significantly lower in the final section of the driven tube.</div><div> </div><div> Approximate frequency responses were computed from pitot-mode responses. The frequency-response amplitude varied by a factor of 5 between 200--1000 kHz due to significant resonance peaks. Measurements with blinded PCB132 sensors indicate that the resonances in the frequency response are not due to vibration. </div><div> </div><div> Using the approximate frequency response measured with the shock tube to correct the spectra of wind-tunnel data produced inconclusive results. Correcting pitot-mode PCB132 wind-tunnel data removed a possible resonance peak near 700 kHz, but did not agree with the spectrum of a reference sensor in the range of 11--100 kHz. </div>

Infrared transition location estimates can be fast and useful measurements in wind tunnel and flight tests. Because turbulent boundary layers have a much higher rate of convective heat transfer than laminar boundary layers, a difference in surface temperature can be observed between turbulent and laminar regions of an airfoil at a different temperature than the free stream air temperature. Various implementations of this technique are examined in a wind tunnel. These include using a heat lamp as an external source and circulating fluid inside of the airfoil. Furthermore, ABS plastic and aluminum airfoils are tested with and without coatings such as black paint and surface wraps. The results show that thermal conduction within the model and surface reflections are the driving issues in designing an IR system for detecting transition. Aluminum has a high thermal diffusivity so is a poor choice for this method. However, its performance can be improved using an insulating layer. Internal fluid circulation was far more successful than the heat lamp because it eliminates the reflected IR due to the heat lamp. However, using smooth surface wraps can mitigate reflection issues caused by the heat lamps by reducing the scatter within the reflection, producing an IR image with fewer contaminating reflections.

A wind tunnel investigation of an axisymmetric bluff body, known as a Goldschmied propulsor, was completed. This model conceptually combines boundary layer control and boundary layer ingestion into a single complementary system that is intended to use energy to reduce the axial force on the body by eliminating separation and increasing the pressure recovery aft of the body’s maximum thickness. The goal of the current project was to design, fabricate, and fully document the performance of a wind tunnel model incorporating the Goldschmied propulsor concept and complete an examination of its aerodynamic performance. The investigation took place at California Polytechnic State University, San Luis Obispo in the Aerospace Engineering Department’s subsonic 3ft by 4ft wind tunnel. The model is 38.5 inches in length and 13.5 inches in diameter with a discrete suction slot at 85% of the body length and an embedded propulsor that provides the suction flow, expelling it out of the model’s aft end. The experiment included measurements of surface pressure, total axial force, suction mass flow rate, fan thrust, fan torque, fan speed, and input fan power. The size of the suction slot and amount of input fan power were the main test variables in the 54 data point test matrix that was completed at a length Reynolds number of 1.34 million and a tunnel speed of 66 ft/s (20 m/s). The model was able to achieve fully attached flow on the aftbody with as little as 100W of input power and a net positive (forward) axial force coefficient of 0.12 with as little as 200W of input power. The model was also able to achieve a peak axial pressure force coefficient of 0.005 in the forward direction with an input power of 500W and a slot gap of 1.6% of the body length. A slightly lower axial pressure force coefficient of 0.0045 was achieved with only 200W of input power and a slot gap of 0.7% of the body length. The peak axial pressure force for most tested slot gaps occurred at about 200W of input power, and a slot gap of 0.7% of the body length resulted in the best overall performance for most input power settings. Two different suction slot configurations, a simple gap and a cusp, were tested, and no significant performance differences were seen between them. The pressure coefficient data showed similar trends as test data from 1956 of a similar model at higher Reynolds number, but it did not show complete agreement. Despite these positive aspects of the investigation, a simple power based comparison between the collected data and a conventional non-integrated propulsor does not show a performance improvement for the Goldschmied propulsor.

<p>This thesis addresses the development and implementation of an experimental methodology for turbine rotors which enables experiments to be performed in the stationary frame. This method enables measurements with increased spatial resolution and reduced probe blockage effects while also reducing the cost and complexity of the experimental apparatus. Adding this experimental method to the turbine designer’s toolbox will enable more rapid design evaluation and iteration, resulting in faster and less expensive development cycles for new turbine designs. To demonstrate the viability of this new methodology it has been used to evaluate a family of high-lift, high-diffusion turbine geometries in a rainbow ring in the Big Rig for Aerothermal Stationary Turbine Analysis (BRASTA) facility at Purdue University.</p>