Executive Summary : | A number of human and robotic landers, such as Apollo lunar module, have landed on Moon and Mars using a propulsive system. In each of these landings, significant Plume-surface Interaction (PsI) effects were observed, which caused severe problems related to visibility, thermal control surface degradation, sand-blasting damage to surrounding hardware. Additionally, PsI effects can cause crater formation leading to stability issues of lander itself. As India plans to carry out human and robotic exploratory missions in the near future, it becomes very important to perform a study on this very important subject, i.e., plume-surface interactions, which is a challenging, multi-physics problem. The present work aims to employ a coupled solver for modeling gas-solid flows associated with interaction of a rocket exhaust (gas plume) with a granular bed (representing planetary regolith). It is a challenging problem to pursue not just from the point of view of involved physics, but also from the computational viewpoint. A specific goal of the proposed work is to develop or validate tools for predicting crater formation and calculating ejecta dispersion (near field) due to interaction of a rocket plume with a granular bed, representing planetary surface. The regolith particle flow caused by a lander due to plume-surface interactions demands an accurate representation of the response of regolith grain material and gas-grain interactions. To this end, it is aimed to employ gas flow solver, coupled with a granular flow solver through appropriate consideration of momentum and energy exchange between the two phases. Depending upon the flow situation, the flow solver will be a conventional CFD solver (open source or commercial) and or or an in-house particle based Direct simulation Monte-Carlo (DsMC) solver that can handle high degrees of non-equilibrium. An open-source and or or in-house DEM solver will be used for modeling granular flows. Noteworthy is the fact that in-house DsMC and DEM solvers are available with the PI. The coupling of two component methods is planned in a two-way coupled manner by exchanging momentum and or or energy between gas and grain phases. Case studies related to crater formation, ejecta dispersion due to plume-surface interactions will be performed by varying several parameters, such as gas and grain (particle) density, grain size, solids fraction, stokes number, distribution of particle size. Plume surface interaction studies for a representative planetary regolith will be performed. The proposed research work is first of its kind in India, and has been attempted at a very few labs in the world. The study bears importance to future exploratory missions of India, as the evaluation of rate of erosion below a rocket exhaust plume of a lander can cause severe effects. Hence, to develop mitigation strategies, it is important to develop and test tools to predict the erosion arising out of plume-surface interactions, which is the aim of this study. |