Direct numerical simulation and parametric study of the noise generated from particle dispersion in decaying homogeneous isotropic turbulent flow

Abstract

The main objective of this study is to understand the noise produced by the dispersion of particles in a simple turbulent flow and to classify the statistics of the particles that influence the noise. The three-dimensional, time-dependent, non-stationary flow-fields of the homogenous isotropic turbulence with microscale Reynold numbers varying from 15 to 50 are computed using direct numerical simulation. 1, 5, 10, 50, and 100 thousand solid particles of varying diameters and densities are randomly injected into the computational domain. The particles' positions, velocities, and temperatures are assessed by integrating the equations of particle motion along each trajectory. The acoustic pressure time history at different far-field observer locations are predicted using the Crighton and Ffowcs Williams (CFW) acoustic analogy for two-phase turbulence. The root mean square acoustic pressures at different observer locations are ensemble-averaged and compared. Three distinct sources of noise from the CFW acoustic analogy are computed, and the effects of particle dispersion on noise sources are presented. The root mean square acoustic pressures increase drastically with an increasing number of particles in the cases of large particles, while the increases in the cases of small particles are not significant comparing to the single-phase flow.