HYDRAULIC RESISTANCE OF RIPPLES

Experiments were conducted to investigate the division of the total shear stress into a friction loss and a form loss component for flows with ripples on the bed. Four different sizes of glass beads were used as bed material, each representing a different value of the dimensionless variable Ξ. The experimental evidence indicates that Y′, the mobility number related to the frictional shear stress, is dependent only upon Y', the mobility number related to the total shear stress. The variable Ξ appears to have an effect only in so far as it determines the value of Ycr, the critical mobility number for the initiation of sediment motion. Inspection of other published data revealed much the same dependence. Copyright © 1988 ASCE.