Fig. 7-8 Speed-up ratio for the generation of 122 x 122 x 16 grids used for a flow calculation around a cylinder on a scalar parallel computer SR2201. By using 32 processors the speed-up ratio of 20 was attained.

Fig. 7-9 An example of the grid generation around a high-speed vehicle by using the general-purpose grid generating system. By looking at the figure from the upper-left subfigure, and following the arrows, a three-dimensional grid structure is generated, through the processes of: entering the shape data, grid generation at the boundary edges, and the grid generation at the boundary surfaces. In the upper-right subfigure the final result has been enlarged. The above processes are very easily carried out with the help of GUI.

When one solves partial differential equations by the finite difference method (FDM) or the finite element method (FEM) for analyses of the fluid motion or the structural mechanics, the computational domain should be first divided into an appropriate grid structure. Previously, the grid generation process has not been the leading part of the numerical simulation, and it remained unnoticed behind the scenes. Recently, however, with the progress of high-speed parallel computers, large-scale complicated computations are carried out rather easily, and the grid generator, though it is still a by-player of a simulation, comes into the spotlight. The reason is that the computation time necessary for the grid generation is not negligible for the large-scale computation with an enormous number of grid points, and that the grid generation itself becomes a very complicated task for the case with boundaries of a complicated shape. Under this situation we developed a general-purpose grid generator system for parallel computers. This system provides, as a matter of course, the various functions required as a general-purpose grid generator and, we gave special priority to the fact that it is oriented to parallel computers. For example, the grids are generated for numerical simulations carried out on parallel computers, and moreover, the grid generation itself is carried out on a parallel computer because the grid generation method by using the solution of partial differential equations is very time consuming (Fig. 7-8). As preparation of data for the grid generation requires three-dimensional imagination, the concept of graphic user interface (GUI) is made good use of everywhere. In this way we succeeded in developing a friendly high-speed general-purpose grid generating system. Figure 7-9 shows an example of the use of the system for the grid generation around a high-speed vehicle.

Reference K. Muramatsu et al., Structured Grid Generator on Parallel Computers, JAERI-Data/Code 97-005 (1997).

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