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Notre Dame, IN, United States

Mark Rennie R.,University of Notre Dame | Mark Rennie R.,Hessert Laboratory for Aerospace Research | Nguyen M.,University of Notre Dame | Nguyen M.,Hessert Laboratory for Aerospace Research | And 6 more authors.
33rd AIAA Applied Aerodynamics Conference

An experimental measurement of three components of velocity and associated flow angles by optical tracking of the light emitted by a laser-induced breakdown (LIB) spark is described. The measurements were performed in a blowdown wind tunnel at a nominal flow Mach number of 4.38. The tests showed that flow velocity could be accurately measured using the technique, with a demonstrated flow-angle uncertainty of less than ± 0.2° at the Mach 4.38 test condition. Wavefront measurements through the shock of a 20° wedge were also performed, and indicated that the measurements could also be performed through a shock with negligible effect on spark formation due to the much smaller aperture of the LIB laser beam in relation to the wavelength of the shock aero-optical effect. © 2016, American institute of aeronautics and astronautios. All right reserved. Source

Mark Rennie R.,University of Notre Dame | Mark Rennie R.,Hessert Laboratory for Aerospace Research | Kane T.,University of Notre Dame | Kane T.,Hessert Laboratory for Aerospace Research | Cain A.B.,Innovative Technology Applications Co.
42nd AIAA Thermophysics Conference

The development from basic fluid-mechanic principles of a mathematical model for the thermal behavior of a closed-circuit wind tunnel is presented. As part of the development of the model, parameters such as total-pressure loss factors and convective heat-transfer coefficients are identified that must be determined from experimental measurement. Techniques for the measurement of these parameters, as well as results for the Mach 0.6 capable 3 Foot Wind Tunnel at the University of Notre Dame, are presented. After incorporating these experimentally-measured parameters into the mathematical model, the model is shown to predict the behavior of the 3 Foot Wind Tunnel with reasonable accuracy. © 2011 by Rennie. Source

Sutcliffe P.,University of Notre Dame | Sutcliffe P.,Hessert Laboratory for Aerospace Research | Vorobiev A.,University of Notre Dame | Vorobiev A.,Hessert Laboratory for Aerospace Research | And 3 more authors.
AIAA Ground Testing Conference

An example of mathematical-model based control is presented, in which a mathematical model for the behavior of a low-speed wind tunnel is used to determine the control inputs necessary to control the test-section temperature during rapid changes in test windspeed. Development of the mathematical model from basic fluid-mechanic equations is shown, as well as the experimental measurements that were performed to determine the values of various model parameters that produce a high-fidelity simulation of the behavior of the actual wind tunnel. The results show that the mathematical model, when properly benchmarked against the actual wind-tunnel performance, can be used for accurate feedforward control of the wind-tunnel temperature, even without a complementing PID loop to reduce residual error. Source

Porter C.,University of Notre Dame | Porter C.,U.S. Air force | Gordeyev S.,University of Notre Dame | Gordeyev S.,Hessert Laboratory for Aerospace Research | And 4 more authors.
AIAA Journal

This paper discusses the aero-optical environment for a flat-window hemisphere-on-cylinder turret over a wide range of viewing angles during flight tests in the Airborne Aero-Optics Laboratory. Aero-optical aberrations around the turret were measured using a high-speed Shack-Hartmann wave-front sensor providing an extensive aero-optical mapping. The primary data were acquired atMach 0.5 at an altitude of 15,000 ft, with a subset of the data collected at Mach 0.4 for verification of scaling relationships. Data were acquired holding the relative position between two aircrafts constant. Additional data sets were acquired allowing two aircrafts to change their relative positions so that slewing data could be acquired; this provided statistical data over a large range of viewing angles between lookingforward to looking-back angles. Results were analyzed, and the aero-optical contribution from different flow features over the turret was identified and discussed. Cross-correlation functions and convective speed were also computed for some viewing angles and compared with other experiments. The flight-test data were also compared to wind-tunnel measurements using the identical turret. Source

Nightingale A.M.,University of Notre Dame | Nightingale A.M.,Hessert Laboratory for Aerospace Research | Goodwine B.,University of Notre Dame | Goodwine B.,State University of New York at Buffalo | And 3 more authors.
AIAA Journal

An alternative adaptive-optic controller, using both flow control and a phase-lock-loop control strategy, has been designed to overcome bandwidth limitations inhibiting current adaptive-optic controllers. Adiscrete-vortex code and weakly compressible model were used to simulate high-speed shear layer adaptive-optic corrections based upon the proposed phase-lock-loop controller given a range of upper and lower Mach numbers. The shear layer was forced at its origin, creating a region of regularized large-scale structures through which a simulated optical beam was projected. The controller applied a predicted conjugate correction to the shear layer's emerging wavefront in a feedforward approach. The phase-lock-loop controller produces a sinusoidal signal for which the amplitude and phase are adjusted in real time to synchronize with the reference input. The controller is designed to track abrupt changes in phase or frequency.An overview of the design process is provided along with the alternative adaptive-optic controller's basic layout and circuitry diagrams. Finally, experimental jitter results illustrate the controller's amplitude and phase response capabilities given a purely sinusoidal function generator input signal. Copyright © 2013 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. Source

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