Cavitation in essence, shares the same physical process as boiling, described in Multiphase module. Fundamentally, both cavitation and boiling are evaporation and condensation process between liquid and vapor phases. However, the mechanisms that trigger the phase changes are different. Cavitation is predominately caused by mechanical effects (the sharp pressure changes) in fluid systems, while boiling is due to thermal effects that raise the vaporization pressure of a liquid above its local ambient pressure to cause the phase change from liquid to vapor. Therefore, cavitation is generally treated separately from the thermal phase changes, as the cavitation process is typically too rapid to assume thermal equilibrium at the liquid-vapor interface. In fact, in many standard cavitation models, the mass transfer is treated as driven purely by liquid-vapor pressure differences, though thermal effects can be included by allowing the phase densities and most importantly, the saturation vapor pressure as the function of temperature.
In Simerics-MP, a cavitating flow is considered as a liquid-gas mixture whose density varies with the vapor content generated from cavitation, and the other gaseous components existing in a fluid (non-condensable gases, dissolved gases, etc.). The scalar transport equations are solved for the mixture velocity, pressure, temperature (if thermal effect is included), turbulence and other physical quantities such as a non-condensable gas and dissolved gas. With the occurrence of cavitation, an additional equation for vapor must also be solved to determine how much vapor is generated and transported within the fluid mixture. The modelling theory and cavitation models available in Simerics-MP are described in this section. Specifically, it consists of the following subsections:
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