Study on Multi-Time Scale Hydrodynamic Model Based on Local Time Stepping Scheme and GPUs and its Application in Urban Inundation

In view of the frequent occurrence of urban inundation, this paper establishes a multi-time scale non-uniform grid model that integrates a non-uniform grid division approach, local time stepping scheme and Graphics Processing Unit (GPU) parallel technology to improve computational efficiency. The Harten-Lax-vanLeer-Contact (HLLC) approximate Riemann solution is adopted to estimate interface fluxes, the Monotonie Upwind Scheme for Conservation Laws (MUSUL) and Runge–Kutta methods are adopted to achieve second-order accuracy in time and space. Each grid uses the time step allowed locally to update variables. The results show that the proposed model has certain accuracy and greatly improves the calculation efficiency. When the threshold for grid density is 30%-45% of the average topographic gradient change, the accuracy and the efficiency are optimized in simulation of urban inundation. At this time, the average error of inundation area is about 6.05%, and the simulated speed of the proposed model is about 4.52 times that of the traditional uniform grid model. Therefore, the proposed model has a certain promotion value in large-scale shallow water flow simulations.