A coupled 1D and 2D hydrodynamic model for free-surface flows

A coupled one-dimensional (1D) and two-dimensional (2D) numerical model for free-surface flows is presented. For the 1D model, the finite-difference method is used to discretize the Saint-Venant equations. An implicit dual time-stepping method is applied to a finite-volume model for 2D flows to improve run-time efficiency. Four test cases – one extensive analytical benchmark case, two linking examples and a dam break with actual topography – are applied to validate the proposed model and to demonstrate its performance in comparison with an explicit scheme and published results. The proposed model was found to be accurate and efficient for simulating free-surface flows in practical applications. Two treatment methods for dealing with the boundary of the 2D model at the coupled area are also compared. The results show that using exchange water as a source term is a more stable treatment than as an open flow boundary, with only a small difference in simulation results.