Plume-surface interaction during lunar landing using a two-way coupled DSMC-DEM approach

In the present work, a numerical framework is developed for simulating gas -solid flows associated with interaction of a rocket plume on a planetary surface. For this investigation, a unique, two-way coupled, dusty -gas flow model has been developed in the coupled direct simulation Monte Carlo (DSMC)-discrete element method (DEM) framework, which has been applied for dust dispersion on lunar surface. In this model, the gas -gas collisions are modeled probabilistically, whereas grain -grain interactions are computed deterministically. Most importantly, a multiphase fluid -solid two-way coupling model is proposed where the fluid -particle interaction is modeled macroscopically by considering the momentum and energy exchange between the two phases. The use of the DEM approach allows us to model dense granular phase near a planetary regolith. Additionally, the framework allows us to calculate not only the particle trajectories, but also their temperatures. To make the framework efficient for dynamic calculation of drag and heat transfer from gas to grain phase, the same coefficients are precalculated (and used later as a look -up table) for gas flow over an isolated granular particle over a range of speed ratios for free molecular flow conditions. Using the developed framework, a comprehensive numerical study is performed to model dust dispersion associated with lunar landing. The influence of particle diameter on gas and grain phases and dust transportation has been analyzed in the coupled framework. Additionally, the impact of the two-way coupled gas -grain interaction model is analyzed and compared with one-way coupled model.