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Published January 2022 | Published
Journal Article Open

Amplitude and wall-normal distance variation of small scales in turbulent boundary layers


The spatial organization of small scales around large-scale coherent structures in a flat plate turbulent boundary layer is studied using a conditional-averaging technique applied to experimental and computational data. The technique averages the small-scale velocity conditioned on the projection coefficient between the instantaneous streamwise velocity field and a model for large-scale velocity structures in the wake and logarithmic regions. Two distinct scenarios are identified for the organization of the small scales: amplitude variation, in which at a given wall-normal location the small-scale intensity varies in amplitude across the streamwise extent of the large-scale structure, and height variation, in which the small-scale velocity intensity remains nearly constant along a curve that changed its wall-normal location across the streamwise extent of the large-scale structure. Small scales that are energetic at the wall-normal location where the large-scale structure is centered primarily show evidence of height variation, while small scales that are energetic at wall-normal locations far from the center of the large-scale structure primarily show evidence of amplitude variation. Connections can be drawn between the statistical observations characterized by the amplitude modulation statistic and the structural picture associated with vortex clusters.

Additional Information

© 2022 American Physical Society. (Received 7 October 2021; accepted 3 January 2022; published 20 January 2022) This work was made possible through United States Air Force Grants No. FA9550-12-1-0060 and No. FA9550-16-1-0361 and through a National Defense Science and Engineering Graduate Fellowship. The authors would like to thank Xiaohua Wu for providing access to and support using his computational data. The support of the Center for Turbulence Research at Stanford University and useful conversations there with Kevin Rosenberg and Aaron Towne are also gratefully acknowledged.

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Published - PhysRevFluids.7.014606.pdf


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August 22, 2023
October 23, 2023