高密度和高粘度比率下气液两相流动的数值模拟

本文在VOF方法的基础上,采用粗细两套网格对高密度和高粘度比率下的气液两相流动模拟进行了研究分析.在细网格中求解流体体积函数方程,在粗网格中采用交错网格求解动量方程和压力修正方程,通过粗细网格间的数据传递获得求解动量方程时需要的准确的界面密度和粘度及控制体密度,克服了高密度和高粘度比率下通过插值方法计算界面密度和粘度及控制体密度带来较大误差的困难,保证了质量和动量同时守恒.高密度和高粘度比率下气液两相流动中气液交界面处密度、速度和压力急剧变化,为了保证格式的有界性和稳定性,采用稳定的有界高阶组合格式STOIC.最后模拟了不同工况下气泡在液体中的运动,并通过实验和模拟结果验证了方法的可行性及准确性.

NUMERICAL SIMULATION OF GAS-LIQUID TWO-PHASE FLOWS WITH LARGE DENSITY AND VISCOSITY RATIOS

In this paper,on the basis of the VOF method two sets of grid systems,coarse and fine, are adopted to simulate gas-liquid two-phase flows with large density and viscosity variations.The advection equation of volume fraction is solved on the fine grid system;the momentum and pressure correction equations are solved on the coarse staggered grid system.The accurate densities and viscosities at control volume and its faces used in the process of solving the momentum equations can be calculated by the mutual exchanges of data between the coarse and fine grid systems,which decreases the errors caused by the traditional linear interpolation method and guarantees the exact satisfaction of both momentum and continuity equations.In the gas-liquid two-phase flows the densities,viscosities and velocities have the sharp gradient,hence,the STOIC scheme is adopted ,which possesses the characteristics of stability,boundedness and high accuracy.Finally applications of the numerical method to predict the single gas bubble rising and the co-axial and oblique coalescence of two gas bubbles in quiescent liquids are presented.The bubble terminal velocities and shapes are in good agreement with the available experimental results.