说明：  用MATLAB编写的基于有限体积法求解二维浅水方程边界数值通量的Riemann求解器（HLL格式），可处理干河床问题，适用于规则网格及不规则网格，只需提供边界左右两侧的水深和流速以及外法线矢量
(Written using MATLAB numerical flux based on the finite volume method for solving the two-dimensional shallow water equations boundary Riemann solver (HLL format), can handle the dry riverbed problem, applicable to a regular grid and irregular grid, just on both sides of the border around water depth and flow rate as well as outside the normal vector)