Improved method for converting equivalent sand-grain roughness to Hazen-Williams coefficient

Abstract

A method of predicting the Hazen-Williams roughness coefficient from knowledge of equivalent sand-grain roughness is presented. An equation resulting from combining the Hazen-Williams, Darcy-Weisbach, and Colebrook-White equations is used as the basis of the relationship. This equation in turn is used as the theoretical foundation for correlating existing experimental data for sandgrain roughness and Hazen-Williams coefficient. Previously developed methods have not incorporated such data. The result is a correlation that shows very good agreement between accepted and predicted values, providing an improved means by which conversion of sand-grain roughness to Hazen-Williams coefficient can be accomplished where values for one or the other are not readily available.