|Title:||Response of the wake of an isolated particle to isotropic turbulent cross-flow
|Author(s):||Bagchi, Prosenjit; Balachandar, S.
|Abstract:||The interaction of an isolated spherical particle with an isotropic turbulent flow is
considered using direct numerical simulations (DNS). The particle Reynolds number
is varied from about 50 to 600 and the particle diameter is varied from about 1.5 to 10
times the Kolmogorov scale. The Reynolds number based on the Taylor microscale of
the free-stream turbulent field considered here is 164. The DNS technique employed
here is the first of its kind to address particle–turbulence interaction and it resolves the
smallest scales in the free-stream turbulent flow and the complex vortical structures
in the particle wake. The primary objective of this paper is to present new results
on the effect of the free-stream turbulence on the particle wake and vortex shedding,
and the modulation of free-stream turbulence in the particle wake. The parameters of
the present simulations are comparable to those of the experimental study by Wu &
Faeth (1994a, b), and agreement between the present computational results and the
experimental measurement is demonstrated.
The effect of free-stream turbulence on the mean and instantaneous wake structure
is studied. The time-averaged mean wake in a turbulent ambient flow shows a lower velocity
deficit and a flatter profile. However, in agreement with the experimental results
of Wu & Faeth the mean wake in a turbulent flow behaves like a self-preserving
laminar wake. At Reynolds numbers below about 210 the effect of free-stream turbulence
is to introduce wake oscillations. For Reynolds numbers in the range 210 to
280, free-stream turbulence is observed to promote early onset of vortex shedding.
The nature of the shed vortices is somewhat different from that in a uniform flow.
Increasing the free-stream turbulence intensity suppresses the process of vortex
shedding, and only marginally increases the wake oscillation. The modulation of freestream
turbulence in the wake is studied in terms of the distribution of kinetic energy
and RMS velocity fluctuation. The free-stream energy lost in the wake is recovered
faster in a turbulent ambient flow than in a uniform ambient flow. The energy of the
velocity fluctuation is enhanced in the wake at low free-stream intensities, and is
damped or marginally increased at higher intensities. The fluctuation energy is not
equi-partitioned among the streamwise and cross-stream components. The RMS
streamwise fluctuation is always enhanced, whereas the RMS cross-stream fluctuation
is enhanced only at low free-stream intensities, and damped at higher intensities.
|Publisher:||Cambridge University Press
|Citation Info:||Prosenjit Bagchi and S. Balachandar. Response of the wake of an isolated particle to isotropic turbulent flow. Journal of Fluid Mechanics, Vol. 518, 2004, pp. 95-123.
|Publication Status:||published or submitted for publication
|Peer Reviewed:||is peer reviewed
|Rights Information:||Copyright owned by Cambridge University Press 2004.
|Date Available in IDEALS:||2007-06-18
|Has Version(s):||Previously released as TAM Reports 1047. http://hdl.handle.net/2142/243.