Hybrid grid—a specialized mesh system for full three-dimensional numerical simulation in natural waters

A specialized refined grid system for simulating full three-dimensional natural waters, named hybrid grid system by the authors, is reported in the paper. This system is composed of part orthogonal body-fitted curvilinear coordinates in horizontal directions and part Cartesian coordinates in the vertical direction. In the horizontal plan the orthogonal body-fitted coordinate (BFC) system exactly fits shore lines, in the vertical direction the blockage coefficients approximate the bottom topography. The main principle and particulars of numerical mesh generation have been stated in detail, the established nonsimplified governing equations of fluid movement and temperature transport under the present grid system are also presented. An example of the generation of the hybrid grid system for a 90° curved river reach has been provided, the discretization of governing equations and corresponding result analyses of the numerical computation will be presented in more detail in another paper.