Development of Efficient and Accurate Parallel Computation Algorithm Using Moving Overset Grids on Background Multi-Domains for Complex Two-Phase Flows

Abstract

The goal of this study involves developing an efficient and accurate parallel computation method for two-phase flow problems including complex moving foreign bodies. The proposed parallel computing techniques are based on the moving body-fitted grids’ overset on background multidomains with grid-overlapping at their interface. First, the cavitation flow over the hemispherical head form is investigated using the two-phase flow solver, which is validated by comparing the numerical and experimental results. Subsequently, the parallel computing technique based on the multidomain method that divides the computational domain into several smaller subdomains is proposed to facilitate more efficient numerical simulations. At the interface of the subdomains, the grid-overlapping method is proposed for more accurate simulations. The illustrative computations indicate that the accuracy of the parallel computation combined with the grid-overlapping method on multidomains is identical to that of the serial computation based on a single block, albeit with a significant reduction in the computation time. Finally, the moving overset grid technique is combined with the background multidomain method and applied to simulate the gust flow that is generated by the pitching motions of the twin hydrofoils. The overset grid technique includes the following three sequential steps: hole-cutting, finding donor cells, and bilinear interpolation. The prediction results for the inflow gust generated by oscillating hydrofoils closely follow the measured results.

Numerical Investigation of Tip Vortex Cavitation Inception and Noise of Underwater Propellers of Submarine Using Sequential Eulerian–Lagrangian Approaches

“…In a flow field where the large-scale cavitation structure occurs due to a decrease in the cavitation number, the molecules on the bubble surface are sufficiently far away for one another; thus, the molecular force is negligible. Then, the critical pressure being a function of the only temperature equals the vapor pressure, which is why the cavitation flows, such as sheet and cloud cavitation, have been successfully predicted with the Eulerian methods based on the RANS solver combined with the homogeneous mixture model [34][35][36][37][38][39][40]. However, the Eulerian method has difficulty in accounting for the water quality effect because the critical pressure varies with the initial nuclei size.…”