Experimental study of the flow in the wake of a stationary sphere immersed in a turbulent boundary layer

René Van Hout, Jerke Eisma, Gerrit E. Elsinga, Jerry Westerweel

Research output: Contribution to journalArticleScientificpeer-review

5 Citations (Scopus)
39 Downloads (Pure)

Abstract

In many applications, finite-sized particles are immersed in a turbulent boundary layer (TBL) and it is of interest to study wall effects on the instantaneous shedding of turbulence structures and associated mean velocity and Reynolds stress distributions. Here, 3D flow field dynamics in the wake of a prototypical, small sphere (D+=50, 692<ReD<959) placed in the TBL's outer, logarithmic, and buffer layer, were measured using time-resolved tomo-PIV. Increasing wall proximity increasingly tilted the mean recirculating wake away from the wall implying a negative lift force. Mean velocity deficit recovery scaled with the mean wake length with minor effects of wall proximity. Farthest from the wall, streamwise Reynolds normal stresses encircled the mean wake as an axisymmetric tubular "shell," while transverse and wall-normal stresses extended off its tip as axisymmetric tapered cones. Wall proximity removed axisymmetry and attenuated values near the wall. Reynolds shear stresses were distributed as antisymmetric lobes extending off the mean wake displaying increasing values with reducing sphere-wall gap. Instantaneous snapshots revealed a wake densely populated by "archlike" vortices with shedding frequencies lower than for a sphere in uniform flow except in the buffer layer. Tilting of the wake away from the wall resulted from self-induced motion of shed hairpinlike vortices whose symmetry plane was increasingly wall-normal oriented with reduced sphere-wall gap.

Original languageEnglish
Article number024601
Number of pages28
JournalPhysical Review Fluids
Volume3
Issue number2
DOIs
Publication statusPublished - 2018

Keywords

  • boundary layers
  • fluid-particle interactions
  • turbulence
  • wakes & jets
  • fluid mechanics

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