Turbulence modulation in dense liquid-solid channel flow

Inertial solid particles suspended in dense turbulent channels modulate turbulence and fluid mass flow rate through two mechanisms: (I) the increase of the suspension's apparent kinematic viscosity with increasing solid volume fraction and (II) turbulence modulation through the particle feedback force. For particle volume fractions below 3%, the increase in suspensions apparent viscosity accounts for most of the modulation. As the volume fraction increases, the particle feedback force drives additional modulation beyond what the increased viscosity accounts for. Namely, this is a reduction in the bulk fluid velocity, reduction of turbulent fluctuations, and increased coefficient of friction.