Effect of mixing gas–fine particle suspension flow with small amount of coarse ones in a horizontal pipe

A phase doppler anemometer (PDA) was used to measure axial components of mean and fluctuation velocities of air and particles in a pipe of 80 mm inside diameter. Glass beads having mean diameter of 55 and , respectively, were used, the density being . The fine particles suppress the air flow turbulence while the coarse ones increase it. Mixing fine particles with coarse ones in 5–9% in mass increases the turbulence above that by coarse ones alone. The acceleration pressure drop due to the particles is increased as well above that by the fine particles alone, which is larger than that by the coarse ones alone.