Visual pipeline mechanism and basic structure of the parallel program were discussed based on the characteristics of Visualization ToolKit (VTK). Since the problem of visualization post-processing in computational fluid dynamics, VTK color mapping algorithm was introduced and a program of showing nephogram was written. In order to reduce the running time, a parallel algorithm was proposed. The proposed algorithm made full use of the parallelism between the VTK tasks, reduced the program running time and improved the running efficiency. Finally the speedup ratios of files of different sizes were compared and analyzed. The results show that the requirements of visualization post-processing is satisfied by visualization technology based on VTK and the good parallel effect is obtained with Message Passing Interface (MPI).

Due to the shortcomings of large amount of computational grids and slow convergence rate in the numerical simulation of the complex flow, the parallel algorithm of multiple Cartesian grid generation based on three-dimensional geometry was proposed for Lattice Boltzmann Method (LBM). And multi-grid parallel LBM was developed based on the parallel algorithm of grid generation. The proposed algorithms can efficiently reduce the amount of computational grids and improve the convergence by coupling with the grids with different sizes. Numerical results also show that the proposed parallel algorithms have considerable scalability.