MODELING OF LOCAL SCOUR UPSTREAM OF A WEIR : ORDINARY- DIFFERENTIAL EQUATION BASED MODEL INTEGRATING CLEAR-WATER SCOUR AND LIVE-BED SCOUR CONDITIONS

Abstract

This study presents a practical model for time-varying scouring around a weir under the condition of clear-water scour and live-bed scour for an unsteady flow rate. The model is based on the continuity law of sediment transport and empirical formula for dimensionless scour rate, resulting in a non-linear ordinary differential equation (ODE) of a scoured volume. The model also allows for predicting a maximum depth and horizontal geometric parameters in a scour hole. The present model was validated in scour tests for an unsteady flow rate. The scour topographies for computation and experiment agreed very well. The present model was also compared to a 3D simulation model of sediment transport. The accuracy of the present model was found to be comparable with the 3D simulation model. The validation results implies that the ODE-based model is able to accurately predict long term scour phenomena which are quite difficult to be predict with 3D simulations due to computational costs.