Numerical Insight into the Kelvin-Helmholtz Instability Appearance in Cavitating Flow

Recently the development of Kelvin-Helmholtz instability in cavitating flow in Venturi microchannels was discovered. Its importance is not negligible, as it destabilizes the shear layer and promotes instabilities and turbulent eddies formation in the vapor region, having low density and momentum. In the present paper, we give a very brief summary of the experimental findings and in the following, we use a computational fluid dynamics (CFD) study to peek deeper into the onset of the Kelvin-Helmholtz instability and its effect on the dynamics of the cavitation cloud shedding. Finally, it is shown that Kelvin-Helmholtz instability is beside the re-entrant jet and the condensation shock wave the third mechanism of cavitation cloud shedding in Venturi microchannels. The shedding process is quasi-periodic.

A Simple and Fast Method for Calculating Properties Across a Condensation Shock

A simple procedure for calculating the pressure at the onset and termination of condensation shocks that occur in steam nozzles and steam turbine blade passages is presented. In addition, the location of the termination of the condensation shock with reference to the throat location is also predicted. The procedure is based entirely on thermodynamic and gas dynamic considerations, without using a model for droplet nucleation and growth and the nozzle profile. The only input required is the stagnation condition at the inlet to the nozzle. The procedure requires the solution of a system of algebraic equations which can be accomplished quite easily. Calculations have been carried out for several inlet stagnation conditions and the predictions are compared with the available experimental data. The agreement is seen to be reasonable considering the simplicity of the procedure.

A Simulation of the Liquid Shock and Cavitation Based on a Multi-Equation Model

In this paper, an unsteady preconditioning formulation for multi-phase flows with arbitrary equation of state based on the approximated Riemann solver is developed for multi-phase flows at all speed. This paper considers a homogeneous two-phase multi-equation mixture model with the assumption of kinematics and thermodynamics equilibriums. The thermodynamics behaviors of liquid phase, vapor phase and their phase transitional process are described by a temperature-dependent hybrid equation of state. Benchmark test cases, including one-dimensional (1D) condensation shock in the cavitated nozzle and two-dimensional (2D) cavitated blunt body problem, demonstrate accurate capturing of interfaces, shock waves and cavitation zones.