Turbulence Distortion amongst Particles in a Channel Flow by Lagrangian Measurements.

Abstract

Turbulence distortion by solid particles in a fully-developed channel flow was investigated by Lagrangian measurement technique. Digital particle image velocimetry and a high-speed CCD camera mounted on a shuttle moving with particle mean streamwise velocity were used to simultaneously detect particle and fluid information amongst particles. Two classes of particles at particle volumetric fraction up to 3.32×10-4 were employed to provide characteristic values of length ratio and distance between particles, i.e., inter-particle spacing. Turbulence augmentation by particles greater than the Kolmogorov micro length scale was induced by the region of the high-strain rate and high vorticity on both sides of particles. The Rapid Distortion Theory applied to dispersed two-phase turbulent flows indicated that the directional non-isotropic structure was observed with an increase in particle volumetric fraction. The enstrophy production was enhanced with decreasing values of inter-particle spacing, yieding an increase in the enstrophy amongst particles.