Experimental Investigation of Friction Coefficient in Ribleted Pipes and the Effect of Fine Particles

The effect of fine particles on turbulence damping and reduction of flow friction coefficient in ribleted pipes, have been investigated experimentally. Tests have been conducted in a ribleted pipe with hydraulic diameter of 18.6 mm, and 20 stream wise riblets of 1.8 mm depth, along the pipe. Flows of water tap with Reynolds number from 5000 to 30000 were compared with flows containing silt-clay particles and stone powder of less than 63 micron sizes. In the flows containing 1.6 kg/in3 of stone powder, the pressure drop along the pipe reduced by 25 percent, and with flows containing silt-clay particles, the pressure drop reduction was about 15 percent. Reduction of friction, in flows containing fine particles, may be due to the interaction of particles and turbulence generated at pipe boundary, and damping of this turbulence.