An alternate approach for modelling of transient vaporous cavitation
Simulation of cavitating flow has been a thrust area of research for long period due to its practical and economic importance. The major hurdle in developing a numerical model for such flows is the difficulty in representing the quick phase changes, in general, and the alternate change of flow from single phase to two phase and back, in particular. In this case, instability due to sharp variation of flow characteristics also restricts the development of numerical models. The present study demonstrates the use of a relatively simple formulation for the analysis of flow characteristics in a quasi-rigid pipeline under abrupt phase changes due to cavitation. A popular scheme MacCormack scheme was used for developing a numerical solution for this problem. It uses the conservative form of the governing equations, viz, conservation of mass and momentum, the transport equation and the constitutive relationship. The model can handle variable properties of the water vapour mixture, which is highly compressible. A newly introduced pressure under-relaxation method overcomes the numerical instability due to sharp variation of flow characteristics during phase change. The model could predict the instant of occurrence of vapour pressure, duration of persistence of vapour pressure and the rise of pressure due to vapour collapse to satisfactory levels with published data and experimental results. Copyright (C) 2009 John Wiley & Sons, Ltd.
compressibility vapour collapse transient cavitation variable wave speed pressure under relaxation