Coupling molecular and continuum numerical methods for evaluation of thermal and mechanical drives on high rotating isotopic gas flow

Abstract

The main objective of this study is to develop a hybrid molecular–continuum method to model a gas flow within a centrifuge machine. By implementation of this coupled approach, the effects of mechanical and thermal drives on gas flow and separation process inside a high rotating cylinder are evaluated. In simulating the gas flow inside the high rotating cylinder, there are certain situations where the particle density experiences significant fluctuations. To accurately simulate these events, the direct simulation Monte Carlo (DSMC) approach can be employed as the most effective particle method. However, obtaining a high level of accuracy with this method necessitates a significant amount of computation time. Alternatively, the less time-consuming computational approach, known as fluid technique or computational fluid dynamics (CFD), can be utilized when the flow is in the state of continuum. The goal of coupled DSMC–CFD solution is to integrate particle and fluid simulations to speed up calculation for transitional flows that involve both fields in a unified domain. The DSMC–CFD method is implemented in the OpenFOAM framework to simulate the flow of UF6 gas throughout the regions of a centrifuge machine. This open-source software offers the capability to solve the molecular region and code the coupling between the continuum and molecular regions. This work introduces a modified code based on OpenFOAM to simulate the gas flow in the supersonic rotating cylinder, which provides both molecular and fluid areas. This simulation is conducted under axisymmetric and steady-state to analyze the impact of thermal and mechanical drivers on flow regimes. Also, the isotopic separation and separative work are evaluated.