A Phase-Averaged Analysis of Droplet Dispersion in the Wake of a Square Cylinder in a Uniform Stream

Abstract

Time-averaged and phase-averaged size and velocity distributions of water droplets in the turbulent wake of a square cross-section cylinder, measured with a phase-Doppler anemometer, are presented for a Reynolds number ReD=18,500, based on the free stream velocity, U∞, and cylinder side dimension, D. It is shown that the coherent motion strongly influences the particle distribution and that the mean flow representation can be misleading in interpreting mixing. The results show that small particle concentration is largest in the very near wake. The mean particle distributions are homogeneous as early as 4D downstream of the cylinder, but the influence of vortex shedding on instantaneous distributions persists much longer. It is also observed that at the point of maximum mean streamline curvature, which also coincides with the region of maximum streamwise velocity fluctuations, particle separation is most effective.