Roughness Spacing in Rigid Open Channels

A series of experiments to determine the effect of roughness spacing on open channel flow is reported. The experiments were conducted in an 8-ft wide by 72-ft-long adjustable-slope flume. Roughness elements consisting of sheet metal baffles were placed on the bed of the flume at various longitudinal and transverse spacings. The data are analyzed in terms of the von Karman-Prandtl concepts of turbulent flow near a rough boundary. Logarithmic flow formulas are developed in which the roughness factor is related to the size and spacing characteristics of the roughness elements. The experimental results are compared with those of some other investigators. In addition, some observations are made on the von Karma n turbulence coefficient and the problem of depth determination in rough channels.