Bedform Length and Velocity Pulsations in Alluvial Channels

Abstract

It is conjectured that the low‐frequency turbulence in alluvial channels is engendered at the separation points of the large eddies in the lee of bedforms. These points are taken as the locations of point sources of pressure disturbances, and their influence throughout the flow region is determined using the normal‐mode analysis of the linear hydrodynamic stability theory for inviscid fluids. The analysis predicts that the spatial rate of decay, with respect to depth, of the standard deviation of velocity fluctuations is closely related to the bedform length. The theoretical predictions are borne out reasonably well by the observed data.