Shock-Capturing Characteristics Models for Transient Vaporous Cavitation in Pipe Flow

This paper deals with models based on the method of characteristics (MOC) to reproduce transient cavitating pipe flows and presents a procedure to enhance such models' performance. Proper numerical treatments, including predictor-corrector steps, are presented of the term pertaining to vapor in the characteristics equations for a liquid-vapor mixture that is responsible for the shocks associated with the condensation of liquid-vapor mixtures back to the liquid phase. Both one-dimensional (1D) and quasi-two-dimensional (2D) models are considered. Computational results of 1D and 2D MOC models, with different numerical schemes' resolution, are compared among themselves, with experimental measurements reported in the literature, and with those of a known shock-capturing numerical model. The comparisons among models and with experimental measurements show that the MOC with the proposed numerical solution reproduces very well the experimental pressure traces, like the shock capturing model: if an explicit scheme is used instead of the predictor-corrector one, numerical results are more anticipated in time with respect to experimental results, increasingly for increasing cavitation severity.