Reflected Shock Tunnel Noise Measurement by Focused Differential Interferometry

Creators: Parziale, N. J.; Shepherd, J. E.; Hornung, H. G.

Abstract

A series of experiments is conducted where a quantitative non-intrusive optical technique is used to investigate disturbances in the free-stream of T5, the free-piston driven reflected shock tunnel at Caltech. The optical technique, focused laser differential interferometry (FLDI), measures fluctuations in density. In the test matrix, reservoir enthalpy is varied while the reservoir pressure is held fixed. The results show the perturbations in density are not a strong function of the reservoir enthalpy. During one experiment, exceptional levels of noise were detected; this unique result is attributed to non-ideal operation of the shock tunnel. The data indicate that rms density fluctuations of less than 0.75% are achievable with attention to tunnel cleanliness. In addition, the spectral content of density fluctuation does not change throughout the test time.

Additional Information

© 2012 American Institute of Aeronautics and Astronautics. Thanks to Bahram Valiferdowsi for the isometric views of the solid model of the facility. Also, thanks to Joe Jewell for helping to compute the run conditions. This work was sponsored by AFOSR/National Center for Hypersonic Research in Laminar-Turbulent Transition, for which Dr. John Schmisseur and Dr. Deepak Bose are the program managers. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of the Air Force Office of Scientific Research or the U.S. Government.

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