An Improved Methodology for the Implementation of Numerical Simulation of Multiphase Flow Systems with High Density Ratios

摘要

An improved methodology is presented in this paper for the implementation of numerical simulation of multiphase flow systems with the ratio of properties, such as the density of the two fluids beside the two-phase interface being as large as up to 1000:1. One group governing equations are established for the whole multiphase flow system with the help of the level set function, which is employed to capture the position and topology changes of the interface. A solver for the Navier-Stokes equations is developed in a staggered Cartesian grid system based on the projection method. Both the three-order Runge-Kuttan formula and a Superbee-TVD (Total Variation Dimishing) scheme are adopted to improve the solution to the advection equation of the Level Set function, and a second-order F.NO (Essentially Non-Oscillatory) Scheme is utilized to mitigate and avoid numerical instabilities resulted from sharp changes in fluid properties and other parameters in the multiphase flow field. Numerical tests indicate that the method developed in the present study is capable of simulating multiphase flow system with a density ratio larger than 1000:1. Numerical simulations are also carried out using the method established in this study for a few typical gas-liquid two-phase problems of large liquid-gas density ratios. The numerical results obtained in this study are in good agreement with the experimental data and the results previously obtained by others, showing that the numerical simulations performed by the present method can reasonably reveal the physical mechanisms behind the problems studied, and that the present method is quite promising in simulating the behavior of moving interfaces in multiphase flow systems.