Applicability of Sediment Transport Capacity Formulas to Dam-Break Flows over Movable Beds

摘要

In this paper, we investigate the extent to which well-known sediment transport capacity formulas can be used in one-dimensional (ID) numerical modeling of dam-break waves over movable beds. The ID model considered here is a one-layer model based on the shallow-water equations, a bed update (Exner) equation, a space-lag equation for the nonequilibrium sediment transport and an empirical formula calculating the sediment transport capacity of the flow. The model incorporates a variety of sediment transport capacity formulas proposed by Meyer-Peter and Miiller, Bagnold, Engelund and Hansen, Ackers and White, Smart and Jaeggi, van Rijn, Ricken-mann, Cheng, Abrahams and Camenen, and Larson. We examine the performance of each formula by simulating four idealized laboratory cases on dam-break waves over sandy beds. Comparisons between numerical results and measurements show that for each case better predictions are obtained using a particular formula, but overall, formulas proposed by Meyer-Peter and Miiller (with the factor 8 being replaced by 12), Smart and Jaggi, Cheng, Abrahams and Camenen, and Larson rank as the best predictors for the entire range of conditions studied here. Moreover, results show that in the cases where a bed step exists, implementing a mass failure mechanism in the numerical modeling plays an important role in reproducing the bed and water profiles.