An alternate approach for modelling of transient vaporous cavitation

Abstract

SUMMARYSimulation 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.

Coupling Quasi-Two-Dimensional Friction Model and Discrete Vapor Cavity Model for Simulation of Transient Cavitating Flows in Pipeline Systems

“…where Q and Q u * are the discharges at the downstream and upstream sides of the cavity, respectively. e numerical integration of equation (6) using the staggered MOC grid can be expressed as…”

“…e pressure heads at the downstream valve of pipe predicted by the proposed quasi-2D model with different Figure 2: MOC method with staggered grid [8]. 6 Mathematical Problems in Engineering weighting coefficients ψ for three cases of the initial mean velocities are presented in Figure 5. e weighting coefficients ε and θ values are both set to 1.00 for three cases of the initial mean velocities in Figures 5(a)-5(c).…”

“…Hydraulic transients with column separation have been explored in some aspects by many researchers [3]. A number of vaporous cavitation models have been developed for simulating transient cavitating flows in pipeline systems [4][5][6]. Among these models, the discrete vapor cavity model (DVCM) combined with the one-dimensional (1D) quasisteady friction model is the classic modelling approach and is widely used [7].…”

Validation of two-fluid model for water hammer in elastic pipes

“…In order to simulate two-phase flow water hammer, Leon et al [22] formulated and evaluated a second-order shock-capturing scheme using the finite volume method. MacCormack scheme was used by Sumam et al [35] to develop and simulate two-phase water hammer flow in a pipe. Zeng et al [39] used both explicit and implicit AUSM-family schemes to multiphase flow simulations.…”