Abstract: Method for treating a moving surface during a transient condition in a computational fluid dynamics system multi-cell computer model, the model having a fixed underlying geometric grid, includes identifying cells in the grid adjacent the moving surface at the beginning of a transient time step and identifying beginning adjacent cell boundaries formed in the grid by the moving surface. The method also includes computing effective thermophysical value fluxes through the beginning cell boundaries in accordance with the sense of the movement of the moving surface relative to the beginning adjacent cells. The method further includes solving transport equations for all the cells to determine cell thermophysical values at the end of the time step, using the computed effective fluxes and reforming the grid to comply with the moving surface at the end of the time step. Apparatus includes a digital computer programmed to carry out the above method.

Abstract: Method and apparatus are disclosed for implementing a geometric multi-cell system dynamics model having an embedded grid, the embedded grid having cells with a finer grid size relative to the grid size of other cells. The apparatus includes a digital computer having a computational fluid dynamics model program stored therein, the program having software for iteratively solving transport equations for thermophysical values for the embedded cells and the other cells, and for solving residual equations for the values for each cell using a multi-grid computation method. The program also has other software for computationally manipulating the embedded grid cells to provide composite cells of the same grid size as the other cells and having averaged residual thermophysical values, for allowing the multi-grid computation method to operate on the embedded grid cells.