Bed-Form Geometry in Sand-Bed Flows

A new method is proposed for predicting relative bed-form height h/d in sand-bed flows. The proposed method is based on the concept of relating energy loss due to form drag to the head loss across a sudden expansion in open channel flows. A unique feature of the proposed method is that it can be applied to various bed forms, i.e., ripples, dunes, antidunes/standing waves, and transitional bed regimes that occur in alluvial flows. The relation thus developed was applied to a large number (251 flows, 14 different data sets) of laboratory and river data, and was found to give good agreement with the observed h/d values. In a comparison of prediction accuracies with seven existing relationships, the proposed method was found to give significantly better agreements with the observed data. Future improvements in the prediction of h/d will depend on improved formulations of the two parameters incorporated in the present relation, i.e., energy loss coefficient K, and the relative bed-form length L/d for various bed configurations. More research is needed to develop better formulations for these parameters.