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A SIMULTANEOUS PHYSICAL AND SPECTRAL ANALYSIS OF THE TURBULENT BOUNDARY LAYER VIA TIME-RESOLVED PARTICLE IMAGE VELOCIMETRY

Jeffrey A. LeHew
Graduate Aerospace Laboratories California Institute of Technology 1200 E. California Blvd, MC 205-45 Pasadena, California 91125

Michele Guala
Department of Civil Engineering University of Minnesota, Twin Cities 500 Pillsbury Dr. SE Minneapolis, Minnesota 55455

Beverley J. McKeon
Department of Aeronautics, Imperial College London, SW7 2AZ, UK; Graduate Aerospace Laboratories California Institute of Technology Pasadena, CA 91125, USA

Resumo

In this study, time-resolved particle image velocimetry (PIV) was performed in wall-parallel planes to investigate both the time evolution of structures in the flow as well as the 3D spatio-temporal spectrum. In particular vortex signatures in wall-parallel planes were studied which were found to correspond closely with the signature of hairpin vortices found in wall-bounded shear flows. Considering the convection velocity of different streamwise-spanwise scale pairs calculated from the spatio-temporal spectrum, it was found that the average convection velocity of highly energetic scales in the range 1.5 < λx/δ < 5.0 and 0.5 < λz/δ < 1.0 was close to the convection velocity of the vortex signatures. Also, this range of wavelengths is similar in size to the streamwise-elongated structures around which these vortices often appear.