Abstract: This paper reports turbulence modulations and the accompanying drag reduction observed in direct numerical simulation (DNS) of particleladen channel flow. The pointforce twoway coupling model is applied to describe the interaction between the particle and the turbulence. Lagrangian tracking approach is used to describe the dynamics of particles, and derive a formula of drag coefficient from NavierStokes equations. Flow visualizations show that turbulence production can be suppressed by particles. Comparing the results of particleladen and unladen flows, the impact of the diameter and number of the particles on friction reduction are examined.

Key words: direct numerical simulation (DNS), drag coefficient, particles, turbulence modulation, twoway coupling