Quasi-smooth flow in pipes

Abstract

This thesis contains the results of a flow analysis for a circular pipe with a quasi-smooth roughness pattern. Seven ring-and-groove test patterns were investigated, all with h/j (h = depression depth, j = depression width) ratios equal to or greater than one. Resistance measurements for the flow of water through the test patterns were taken over a range of Reynolds numbers extending from 10⁴ to 7X10⁵. Finally analytical relations that this flow regime were developed.

The friction loss in quasi-smooth flow was divided in.to two parts: the friction loss due to the stable vortices rotating in the depressions and the friction loss due to pure viscous shear along the crests of the roughness elements. An expression combining these two losses has been derived.

Unfortunately, it was impossible to determine if a system of "geared" vortices did exist or did not exist in the depression whenever the h/j ratio was greater than one. However, it was found that the depth or the depression does not affect the friction loss.