ID 275

Assessing the Importance of Surface Tension Effect for Simulating the Sub-Grid Scale Interaction of Turbulence and Cavitation in Micro-Channel Flows

 

Abstract:

Phase change phenomena resulting in bubble formation and collapse inside micro channels have significant influence on the subsequent jet formation in spray injection processes through their effect on the local flow. Flow turbulence that contributes to the jet formation and break-up processes is enhanced by the growth and violent collapse of cavitation bubbles. At the same time turbulence development is opposed by surface tension effects between the liquid and the vapour and by viscous forces. Many previous works on injector cavitation assume a local mechanical and thermodynamic equilibrium in the small scales and ignore the effect of surface tension as well as its interaction with turbulence. In the current work a phase change framework that accounts for surface tension effects on fluid motion is suggested and implemented within a compressible code based on OpenFOAM. A systematic variation of fluid properties (and thus surface tension effect) and sgs turbulence modelling is performed. The aim is to identify the numerical sensitivity of the code in the prediction of the coupling of phase change phenomena and flow dynamics, occurring at the small scales and their subsequent effect on the large scale flow. Results are compared with literature data for micro-channel flows over a range of cavitation numbers in order to observe transitional turbulent and cavitation effects and to assess the stability of the model.