A Two-Phase Fluid Model for Simulation of Cavitation Phenomena in Pipe-Line Hydraulic Systems

This paper presents the details of a new fluid mathematical model developed for the numerical simulation of hydraulic systems that can work in cavitating conditions. The proposed fluid model allows you to obtain physical properties, i.e. density, bulk modulus, enthalpy, entropy, void fraction and sound speed, of a liquid-vapor-gas mixture so that the mixture itself can be treated as a homogeneous fluid (homogeneous two-phase fluid model). The model was applied in the numerical analysis of pipe-line test cases. in particular, both travelling cavitation, followed by a shock-wave, and fixed cavitation due to the superposition of depression waves, are examined and numerically simulated. Besides, relevant results are shown about sound speed variations in the zones of cavitation. The author is then interested in evaluating the approximation affecting the results obtainable by using an isothermal approach, by comparing them to the results obtainable by solving the full set of conservation equations (including the energy conservation law). An analysis on the entropy production due to the propagation of shock waves is proposed, along with an estimation of the inaccuracies occurring if an isentropic or isothermal evolution is assumed.