Turbulent boundary layer approaches to resistance coefficient in quasi-rough circular pipes and gravel bed rivers

Abstract

A logarithmic velocity profile has been used, in conjunction with a formulation for the origin of the profile, to study the nature of wall roughness and influence of roughness elements on turbulent flow through circular pipes with part smooth, part rough walls. Experimental data on velocity distribution and frictional head loss have been used to derive expressions for surface characteristics of pipes with uniform and non-uniform wall roughness surface characteristics equations representative wall roughness have been developed for use in the hydraulic design of pipes in the transition zone. In this paper also an experimental investigation is carried out in order to study the effect of concentration of coarse roughness elements on the friction factor. The investigation has shown that it is possible to represent indirectly the effects of concentration by using d₈₄ or d₉₀ as characteristic diameter on gravel bed rivers.

Keywords: velocity profile, frictional head loss, resistance coefficient

Nigeria Journal of Pure and Applied Physics Vol. 4(1) 2005: 90-95