CAVITATING BUBBLY FLOW COMPUTATIONS BY MEANS OF MIXTURE BALANCE EQUATIONS
In this work mixture balance equations are applied and assessed for the simulations of compressible gas-liquid bubbly flows. Main points of interest involve the relative velocity equation that describe the difference between the gas and liquid momentum equations. With the aid of this equation, standard properties of the solutions of the model equations are found. It is shown that, for fully non-equilibrium processes, the governing equations render a simple, conservative and hyperbolic formulation which allows for the application
and extension of well-developed numerical methods of single-phase flows under various bubbly flow conditions. The bubbly mixture model is applied for the simulation of representative two-phase flow problems involving wave propagation phenomena such as cavitating and non-cavitating flows by means of Godunov-type methods. The effects of the relative velocity and gas void fraction are also numerically investigated. The
results demonstrate the importance of using mixture formulations in the simulations of bubbly flows on the
basis of non-equilibrium processes. In contrast, the simulation results are validated by comparison with other
two-phase flow models which fail to reproduce these effects by means of this relative velocity equation. The disagreement lies mainly in the basic assumption of the relative velocity between phases, rather than in the numerical method used. The results are also discussed carefully and validated by other numerical methods. The favorable results suggest that the model equations can be used for reasonable engineering computations of the overall flow conditions in the non-equilibrium processes.