Reservoir Turbidity Current Modeling with a Two-Dimensional Layer-Averaged Model

Abstract

A two-dimensional layer-averaged model is developed and verified to simulate turbidity current characteristics and its sluicing in reservoirs. The governing equations consist of mass and momentum conservation laws for the turbidity current mixture, equations for the sediment transport and bed dynamics, and auxiliary relations for the interactions among clear water, turbidity current, and bed. A finite-volume, unstructured, polygonal mesh method is adopted so that reservoirs with complex terrains may be simulated. Special algorithms are developed to capture the turbidity current front movement through a clear water bed and to simulate turbidity current sluicing through reservoir outlets. The developed model has been tested and verified with both conservative and nonconservative turbidity currents ranging from simple to complex reservoir terrains. Case studies presented include a lock-exchange turbidity current with large eddy simulation and direct numerical simulation results, a laboratory test of turbidity currents, and a physical model of turbidity currents at Shihmen Reservoir in Taiwan. Comparisons of model results with available data show that the developed model, with appropriate calibration, reasonably predicts the turbidity current movement through reservoirs, the resultant sediment deposition along the reservoir bottom, and sediment sluicing through bottom outlets. The study also points to the need for future model improvements.