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 ۱۸.۶ mm, and ۲۰ stream wise riblets of ۱.۸ mm depth, along the pipe. Flows of water tap with Reynolds number from ۵۰۰۰ to ۳۰۰۰۰ were compared with flows containing silt-clay particles and stone powder of less than ۶۳ micron sizes. In the flows containing ۱.۶ kg/in۳ of stone powder, the pressure drop along the pipe reduced by ۲۵ percent, and with flows containing silt-clay particles, the pressure drop reduction was about ۱۵ 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.