Experimental investigation of particle-fluid interaction in turbulent channel flow

Experimental analysis of dilute suspension flow in a turbulent channel was performed using time-resolved particle image velocimetry and particle tracking velocimetry. The active particles had a mean diameter of 230 um and a relative density of 1.15. The mean particle volume fraction varied between 1.3x10 ^-4 and 1.8x10 ^-4. The particle properties and concentration were chosen to simulate the properties of light sand suspensions in oil pipelines, while ignoring particle wetting effects. Three experiments with Reynolds numbers 10,000, 20,000, and 30,000 are presented. The mean velocity profiles of the carrier fluid (water) was not significantly modified by the presence of particles except at Reynolds number 30,000 where the mean fluid velocity was enhanced along the top half of the channel. This is attributed to the low particle concentration of particles in this region. Particle settling is observed in the two lower Reynolds numbers tested. Results indicate a strong influence of the motion of settling particles on the carrier fluid turbulence. Turbulence is suppressed over the bulk of the flow but there is a strong enhancement of the wall-normal turbulence in the Reynolds number 20,000 case, compared to the other two cases. This behavior is attributed to the flow being in transition from a settling suspension to fully suspended flow conditions.