Discontinuous Galerkin simulation of rarefied dusty gas flows based on a second-order Boltzmann continuum model

The rocket plume impingement on the lunar surface can cause significant dust dispersal when the lunar lander approaches the landing site. In this work, we aim to study the rocket plume-lunar surface interaction and subsequent regolith particle dispersal within the Eulerian framework. The subjects are challenging due to the facts that, first, the conventional NSF equations may not be valid in rarefied dusty gas flows; second, the flow physics becomes inherently multi-physics, multi-scale problem in which the erosion of regolith, the interaction of gas and solid particle, and the dispersal of dust are coupled; and lastly, it is impossible to reproduce the lunar condition—characterized by micro-gravity, near-vacuum, and unique properties of the regolith—for an experimental test on the earth. Here, using a modal explicit discontinuous Galerkin method of a second-order Boltzmann continuum model that can cover both the continuum and free-molecular flows with a single framework, inherent complexities consisting of various flow regimes—the plume expanding in vacuum, shock and stagnation regions, local erosion, supersonic dusty jet flow, rarefied flow—are investigated in detail.