Narrow Results

This paper presents an adaptive grid subdivision algorithm based on the Youngs' interface reconstruction algorithm to treat the advection of the mixed grids in the multi-material Eulerian method. The advantage of this algorithm is that it only needs to calculate the advection between pure grids, escaping the complexity encountered in the advection of mixed grids with two materials. In addition, this algorithm is a multi-dimensional advection algorithm, and it can decrease the error encountered in the direction-split advection algorithm. In order to verify the efficiency of the proposed adaptive grid subdivision algorithm in the actual physical field, it is added to the indigenously developed EXPLOSION-2D simulation software, and some numerical tests are performed to demonstrate the utility of this algorithm. The simulation results verify that the adaptive grid subdivision algorithm is simple and efficient.

In this paper, a parallel Eulerian hydrocode for the simulation of large scale complicated explosion and impact problem is developed. The data dependency in the parallel algorithm is studied in particular. As a test, the three dimensional numerical simulation of the explosion field in an unlimited atmosphere is performed. The numerical results are in good agreement with the empirical results, indicating that the proposed parallel algorithm in this paper is valid. Finally, the parallel speedup and parallel efficiency under different dividing domain areas are analyzed.

We adopted operator splitting method to solve the governing equations of explosion and impact problems, and used fuzzy interface treatment to crack 3D multi-material interface difficulties. Then based on message passing interface (MPI), the data dependence and relevance between adjacent subdomains in parallel computing of the Eulerian method were studied and analyzed. At last, we numerically simulated blast in air and shaped charge jet using PMMIC-3D hydrocode, and performed empirical and experimental comparisons. The results show that the cell spatial step has important influence on computational accuracy, and the calculating result with smaller cell spatial step is close to the empirical formula one. Therefore, it is necessary to develop parallel computing to enlarge the calculation scale at smaller cell spatial step for the explosion and impact issues.

Prediction of particle transport in enclosed environment is crucial to the welfare of its occupants. The prediction requires not only a reliable particle model but also an accurate flow model. This paper introduces two categories of flow models — Reynolds Averaged Navier-Stokes equation modeling (RANS modeling) and Large Eddy Simulation (LES); as well as two popular particle models — Lagrangian and Eulerian methods. The computed distributions of air velocity, air temperature, and tracer-gas concentration in a ventilated room by the RANS modeling and LES agreed reasonably with the experimental data from the literature. The two flow models gave similar prediction accuracy. Both the Lagrangian and Eulerian methods were applied to predict particle transport in a room. Again, the computed results were in reasonable agreement with the experimental data obtained in an environmental chamber. The performance of the two methods was nearly identical. Finally the flow and particle models were applied to study particle dispersion in a Boeing 767 cabin and in a small building with six rooms. The computed results look plausible.