Turbulent Friction Drag of a Dusty Gas : Part 1, Theoretical Study

Abstract

The mechanism of a reduction of turbulent friction drag of a dusty gas is studied. The viscous sublayer of the dusty gas is increased with an increase of turbulence energy dissipation due to the presence of dust particles without producing additional turbulence energy, and is dependent on the kinematic viscosity of the gas, the friction velocity, the relaxation time of dust particle and the mass concentration of dust. Assumptions used in this analysis determine the minimum friction velocity, the maximum mass concentration, the maximum density ratio and the maximum particle size of dust at which the drag reduction occurs. For an air of normal temperature the minimum friction velocity is 0.053m/sec and the maximum particle diameter is 142μ. The reduction rate is relatively small and is decreased with an increase of friction velocity for given dust particles.