Roughness effect on particle laden turbulent channel flow

Particle-laden turbulent suspensions of inertial particles are ubiquitous, occurring naturally as well as in industries with highly inertial particles. Fluid Turbulence gets attenuated with relatively small size particles, whereas it gets amplified for larger size particles. It has been reported that turbulent disruption happens discontinuously for wall-bounded flows. The objective of the present study is to quantify the effect of particle and wall roughness on turbulence modulation. Point-particle Direct numerical simulations (PP-DNS) are carried out for a vertical channel, including the roughness in particle-particle and particle-wall interactions. The Reynolds number based on the channel width and average airflow velocity and viscosity Re = 5600 is considered. The particle Reynolds number based on the particle diameter and root mean square of the difference in the particle and fluid velocities is in the range of 4–15. The particle volume fractions are 0–3.5×10^-3, and the particle Stokes number is 200. It is observed that irrespective of the nature of particle-particle interactions, only the particle-wall interaction majorly controls the dynamics of the flow inside the system. With an increase in the roughness between wall-particle interaction, the second moments of the velocity fluctuations increase. However, the particle mean velocity decreases, and fluid velocity becomes more flat at the center core. The rough particle-wall interaction leads to an early collapse in the fluid phase turbulence.