Notre Dame, IN, United States
Notre Dame, IN, United States

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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 | Year: 2015

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.


Gordeyev S.,University of Notre Dame | Gordeyev S.,Hessert Laboratory for Aerospace Research | Juliano T.J.,University of Notre Dame | Juliano T.J.,Hessert Laboratory for Aerospace Research
46th AIAA Fluid Dynamics Conference | Year: 2016

Results of aero-optical measurements of the naturally occurring transitional structures, turbulent spots, and second-mode wave-packet structures in the hypersonic laminar boundary layer are presented. Optical spectra of turbulent spots were similar to spectra for the fully turbulent boundary layers and the average thickness of the boundary layer during the turbulent spot was approximately 50% of the fully turbulent boundary layer. The convective speed of the leading edge of the spot was measured as 0.95 of the freestream speed, while the trailing edge moves at 0.7 of the freestream speed. The dominant frequency of the wave-packet structures was about 70 kHz, consistent with the theoretically predicted second-mode frequency; the average convective speed of the packets was measured as 0.88 of the freestream speed. Using the frozen-field hypothesis, the wavefronts were stitched together to reveal streamwise/spanwise topology of the packets. The packets were found to be fairly narrow, about 2-3δ in the spanwise direction, extending for 30-60δ in the streamwise direction, and having an unusual “reverse-bow” topology. © 2016, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.


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 | Year: 2011

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.


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 | Year: 2013

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.


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 | Year: 2013

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.


Smith A.E.,Hessert Laboratory for Aerospace Research | Smith A.E.,University of Notre Dame | Gordeyev S.,Hessert Laboratory for Aerospace Research | Gordeyev S.,University of Notre Dame | And 2 more authors.
45th AIAA Plasmadynamics and Lasers Conference | Year: 2014

Aero-optic measurements of turbulent boundary layers were performed in wind tunnels at the University of Notre Dame and California Institute of Technology for heated walls at a range of Reynolds numbers. Temporally resolved measurements of wavefronts were collected at a range of Mach numbers between 0.03 and 0.4 and the range of Reθ between 1,700 and 20,000. Wavefront spectra for both heated and un-heated walls were extracted and compared to demonstrate that wall heating does not noticeably alter the shape of wavefront spectra in the boundary layer. The effect of Reynolds number on the normalized spectra was also presented, and an empirical spectral model was modified to account for Reynolds number dependence. Measurements of OPDrms for heated walls were shown to be consistent with results from prior experiments, and a method of estimating OPDrms and other boundary layer statistics from wavefront measurements of heated-wall boundary layers was demonstrated and discussed.


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 | Year: 2013

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.


De Lucca N.,University of Notre Dame | De Lucca N.,Hessert Laboratory for Aerospace Research | Gordeyev S.,University of Notre Dame | Gordeyev S.,Hessert Laboratory for Aerospace Research | And 2 more authors.
43rd AIAA Plasmadynamics and Lasers Conference 2012 | Year: 2012

The optical environment around both a hemisphere-on-cylinder turret and a hemisphereonly turret with flat and conformal windows was characterized at both subsonic and transonic speeds. Data was taken from Mach 0.4 to 0.65 at altitudes from 15,000 ft to 30,000 ft to analyze scaling laws, with a focus on Mach numbers of 0.5 and 0.65. A 25 kHz Shack-Hartmann wavefront sensor was used to measure the optical aberrations around the turret. Data were primarily collected while the two planes slewed by, giving statistics at several azimuthal/elevation angles with additional data taken at fixed angles. Additionally, dynamics of a local shock appearing on the conformal-window turret at the transonic Mach number are presented and discussed. © 2012 by De Lucca N. G., Gordeyev S. and Jumper E. Published by the American Institute of Aeronautics and Astronautics, Inc.


Smith A.E.,University of Notre Dame | Smith A.E.,Hessert Laboratory for Aerospace Research | Gordeyev S.,University of Notre Dame | Gordeyev S.,Hessert Laboratory for Aerospace Research | And 2 more authors.
43rd AIAA Plasmadynamics and Lasers Conference 2012 | Year: 2012

Results of experimental measurements of aero-optical distortions caused by turbulent boundary layers at subsonic speeds M = 0.4...0.6 are presented. Measurements were performed using a high-speed Shack-Hartmann sensor and a Malley probe to collect instantaneous wavefronts with high spatial and temporal resolution. Effects of different aperture sizes on levels of aero-optical aberrations and correlation lengths in both spanwise and streamwise directions are compared and discussed for both wavefront sensors. Detailed statistical analysis of spatial and temporal spectra of aero-optical distortions is presented. Analytical method to predict levels of aero-optical distortions and streamwise correlation lengths for different aperture sizes is proposed and it was found to agree with experimental results. The contribution of boundary-layer large-and small-scale structures on overall level of aero-optical distortions is examined and discussed. © 2012 by Smith, Gordeyev, and Jumper. Published by the American Institute of Aeronautics and Astronautics, Inc.


Gordeyev S.,Hessert Laboratory for Aerospace Research | Neuharth L.,Hessert Laboratory for Aerospace Research | Thomas F.O.,Hessert Laboratory for Aerospace Research | Wicks M.,Hessert Laboratory for Aerospace Research
41st AIAA Fluid Dynamics Conference and Exhibit | Year: 2011

Motivated by closed-loop flow control applications, a formulation of the proper orthogonal decomposition (POD) is demonstrated which is capable of characterizing not only the controlled and natural states of a given flow, but also the transient behavior between these states. This approach, which is termed temporal POD (TPOD) extracts the optimum frame-of-reference and the temporal information regarding the dynamics of the system in the presence of the flow control. In this paper the TPOD approach is applied to two experiments using active flow control: (1) flow over a circular cylinder at subcritical Reynolds number and (2) flow over a NACA 0015 airfoil at a post-stall angle of attack. Both flows exhibit well-defined and distinct natural and controlled flow states. TPOD is shown to be a very effective tool in characterizing these two states as well as the system trajectories associated with the transient behavior in between. © 2011 by Stanislav V. Gordeyev and Flint O. Thomas.

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