Critical Analysis of Open-Channel Resistance

Despite continued progress in the analysis of closed-conduit and boundary-layer resistance, many of the results have been slow to find their way into the hydraulics of open channels. In this paper an effort is made to take greater advantage of existing knowledge in related fields, largely through findings from a continuing program of research in which the writer has been engaged for several decades. The general resistance function is examined under the following interdependent categories: Effects of viscosity, roughness, and shape of cross section; effects of boundary nonuniformity; and effects of unsteadiness, particularly free-surface instability. Special attention is given to such matters as integration of the logarithmic velocity law, variation of roughness form and concentration, channel choking in the critical region, and resistance augmentation by both standing and traveling waves.