Numerical Modelling of Sediment Transport at Weirs.

Abstract—A weir is a barrier across the width of a river or stream, which is commonly used to measure or regulate flow and water elevation. Constructing a weir can alter the characteristics of the flow and sediment transport in the river reach. In order to capture complex local patterns of the flow and sediment transport near structures, three-dimensional (3D) modelling is needed. However, two-dimensional (2D) morphological simulations are frequently carried out to investigate the long-term effect of such structures on morphological alterations at larger scales due to their lower computational effort. It is thereby important that the physical processes around such hydraulic structures need to be simulated with a reasonably accurate model in these situations. At present, the clear water module TELEMAC-2D of the model system TELEMAC-MASCARET has only offered the possibility to simulate water flow at unregulated weirs in a computationally efficient manner. The present paper shows, how the sediment transport module SISYPHE of the system is adapted and extended in order to integrate weirs in hydromorphological simulations with minimal modelling effort. Analogous to the implementation in TELEMAC-2D, the boundary condition at the weir nodes is defined internally in the main program sisyphe.f as liquid boundary in a way that bedload flux can be considered. Subsequently, the bedload flux coming from the upstream side of the weir is transferred to the downstream one by modifying the subroutine conlit.f according to the proportion of each grain fraction. Conducting simulations in a study case verifies the correctness of the new implementation, where the sediment fluxes are compared as well as the total volumes of the present sediment evaluated.     «

Abstract—A weir is a barrier across the width of a river or stream, which is commonly used to measure or regulate flow and water elevation. Constructing a weir can alter the characteristics of the flow and sediment transport in the river reach. In order to capture complex local patterns of the flow and sediment transport near structures, three-dimensional (3D) modelling is needed. However, two-dimensional (2D) morphological simulations are frequently carried out to investigate the long-term effe...     »