68th Annual Meeting of the APS Division of Fluid Dynamics (November 22, 2015 — November 24, 2015)

P0012: Hairpin forest in the upper region of the fully-turbulent flat-plate boundary layer

  • Xiaohua Wu, Royal Military College of Canada
  • Parviz Moin, Stanford University
  • James Wallace, University of Maryland
DOI: https://doi.org/10.1103/APS.DFD.2015.GFM.P0012

Fluid dynamists around the world have been searching for the most basic constitutitve vortex element of turbulent flat-plate boundary layer over the past 60 years, counting from the hairpin model of Theodorsen (1952). The  issue is a profound one since it relates to whether human beings understand even the simplest type of external flows.  Other current structural models in competition include random worms, and cluster of tangled tubes. This image shows that over the momentum-thickness Reynolds number range from 2100 to 3000, in the upper region of the zero-pressure-gradient, fully-turbulent flat-plate boundary layer, the prevailing vortex elements form a forest of hairpin vortices. This is consistent with the earlier work of Wu and Moin (2009) on the structures of transitional and early-turbulent boundary layers. The present image was extracted from our direct numerical simulation database with 4 billion grid points.    

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