In this work, we propose a new computational model to carry out gas-granular flow dynamics within the framework of the direct simulation Monte-Carlo method. The effect of granular particles in hypersonic flow of argon over a 2D cylinder is investigated. In this computational model, the gas-gas collisions are modeled through regular procedures of the direct simulation Monte-Carlo method. The granular particle is considered as a hard solid sphere undergoing inelastic collisions with gas and granular particles. The granular-granular particle collisions are modeled deterministically while considered dissipative with a finite coefficient of restitution. On the other hand, gas-granular interaction is modeled by the consideration of volumetric forces (drag) exerted by gas on the granular particles. In addition to the drag, the skin friction heating associated with gas-granular interaction is also modeled in the present work. The total loss of collision energy in a cell during dissipative granulargranular and gas-granular interactions is then accommodated as heat locally to the surrounding gas. With the new computational approach in hand, we have tested gas-granular flow dynamics in high speed flow regime. We have brought out the important effects of granular particles on pure gas flow structures, such as shocks, wakes, and flow/surface properties in high speed flows.
Translational and rotational dynamics of a transporting particle in the free molecular gas flow regime are investigated using an in-house, multi-species, three dimensional Direct Simulation Monte Carlo (DSMC) solver. The DSMC algorithm is modified to study free molecular gas flows and validated against the analytical results for the dynamics of a spherical particle. A particular focus of this work is on estimating the effects of particle size, shape, and orientation on the dynamics of an ellipsoidal particle in free molecular gas and comparing them with that of a spherical particle. Properties such as particle speed, temperature, drag, and heat transfer coefficients are considered for comparison. The effect of particle shape on the aforesaid properties is qualitatively discussed and quantified through a comprehensive analysis taking care of lift, pitching moment, particle rotation, and the associated resistive torque. The relaxation of an ellipsoidal particle to surrounding gas conditions is simulated at zero and non-zero angles of attack to demonstrate the effect of particle orientation. Furthermore, the particle size effect on its translational and rotational dynamics is discussed. Finally, the trajectory of a spherical particle is compared with that of an ellipsoidal particle at different eccentricities.
A novel, two-way coupled, dusty-gas flow model has been developed in the direct simulation Monte Carlo (DSMC) framework and employed for the dust-dispersion study on lunar surface. In this model, the gas–gas collisions are modeled probabilistically, whereas, grain–grain interactions are computed deterministically. Most importantly, the gas–grain interactions are modeled in a two-way coupled manner through the consideration of momentum and energy exchange between the two phases. The proposed model is validated against the two-phase theoretical relations for a zero-dimensional simulation. The computational model is used to study the dust dispersion problem due to plume impingement on lunar surface. The influence of particle diameter and hovering altitudes on gas and grain phases, and dust transportation are analyzed in the modified DSMC framework. Furthermore, the sensitivity of the two-way coupled gas–grain interaction model is discussed in relation to the one-way coupled model.
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