Mahdi Aghaie

The effective separation of the desired isotope of the elements that are necessary for nuclear applications is a major challenge. Gas centrifuge technology is the most efficient method for isotopic separation, which takes advantage of highly compressible flow. This paper uses ANSYS Fluent software to simulate the behavior of gas in a centrifugal machine with an axially symmetric model in steady state of a high rotating experimental facility. Integrated Computer Engineering and Manufacturing software is used to grid the rotor's geometry in two-dimensional coordinates. The k–ε Re-normalization group model has been used to examine the effects of turbulence on the gas flow inside the rotor because of its acceptable accuracy in a variety of turbulent flows. Following the grid independence study, the simulation's first section examined the changes in mass flux, temperature, and velocity along the radial layers in laminar and turbulent flows. The impact of operating parameters, such as feed flow rate, waste scoop swirl velocity, and temperature differential between the caps, has been assessed in the following to determine the optimal separation power and overall separation factor in both laminar and turbulent flow regimes. The results show that the assumption of laminar flow produces a relative error of 22.7% and turbulent flow produces a relative error of 6.3% in comparison with the measured separation power of the high rotating experimental facility.

The primary objective of this work is to study bellows effect in a compressible rotating isotopic flow using appropriate hybrid numerical model by focusing on evaluating continuum solvers. The hybrid numerical model will be used to analyze the bellows and operating parameters characteristics on separation power. In this regard, two coupled particle–continuum computing frameworks are developed to model supersonic flow inside a gas centrifuge machine for uranium enrichment. These approaches are intended to be more accurate than conventional fluid dynamics solutions (CFD) and more rapid than most pure molecular methods (direct simulation Monte Carlo, DSMC). This study presents a review and the performance comparison of two solvers from the open-source CFD tool OpenFOAM®: the solver based on the rhoSimpleFoam algorithm (PISO and SIMPLE) and rhoCentralFoam which are specifically created for conducting compressible transient and utilize central-upwind schemes for convective fluxes. These are renowned for their ability to effectively balance accuracy and robustness in accurately capturing shock waves and steep gradient phenomena. In this analysis, a coupled DSMC–CFD approach is employed to integrate the modeling of particle and fluid domains to improve the computational efficiency for transitional flows that involve continuum and molecular flows. The DSMC–CFD method is developed into the OpenFOAM framework to simulate the UF6 gas flow in whole regions of a centrifuge machine. OpenFOAM allows solving the molecular region and modeling the interaction between the continuum and molecular flows. In this study, the chosen coupled method is employed to investigate the drives, including bellows and feed mechanisms, in the separation process of a gas centrifuge, as well as the separation power.

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.