Modeling Cryogenic Two-Phase Fluid Transients: A Numerical Investigation of Rapid Valve Closure

A fluid transient occurs when abrupt changes in flow characteristics happen within a fluid network, often due to rapid valve opening or closure or the failure of fluid handling components. This leads to a pressure surge, followed by pressure wave oscillations. When these pressure fluctuations approach or drop below the vapor pressure, cavitation may occur. Cryogenic fluid handling systems frequently face the risk of such fluid transients. Cavitation is marked by the formation and collapse of bubbles caused by high-pressure gradients. Bubbles near solid surfaces collapse rapidly, generating high-velocity jets and pressure waves. The resulting pressure can exert stresses on materials exceeding their yield strength, potentially causing damage.

This study aims to numerically model two-phase fluid transient-induced cavitation resulting from the abrupt closure of a valve. It employs the finite volume computational fluid dynamics (CFD) approach. Additionally, a one-dimensional numerical model is developed using the Method of Characteristics (MOC) and incorporates the Rayleigh-Plesset equation for bubble dynamics. Comparing results from both models reveals that CFD outperforms MOC due to its ability to account for radial variations and visualize two-phase fluid transients more effectively. However, it is worth noting that the MOC method is computationally more cost-effective than CFD.