Simulation of Water Quality Influence on Cavitating Flows (KONKAV)
Background
Cavitation nuclei - i.e. gas bubbles or solid nuclei - or are omnipresent in technical liqiuds and determine the liquid strength. The cavitation phenomena refers to the dynamic interacton between the nuclei and the flow field. Accordingly, the amount and type of nuclei, next to turbulence/bubble-interaction significantly influence the cavitation behaviour.
The project aims to assess the respective influences in a joint co-laborative numerical/experimental research initiative between two universities (Uni Rostock, TUHH) and two model basins (SVA Potsdam, HSVA Hamburg) und the aegis of the BMWi-project KONKAV. The research performed at TUHH is primarily concerned with the development of improved cavitation models to account for bubble-flow interaction. The focal point is on the development of hybrid (teo-way coupled) Euler-Lagrange approaches to mimic the liquid behaviour in conjunction with scale resolving turbulence modelling practices. Moreover attention will be given to techniques which aim to bridge between traditional Eulerian and Euler-Lagrange methods.
Methodology
As a somewhat unusual approach, the present research also follows a coupled Euler-Lagrange technique. This mimics the evolution of cavitation via individual Lagrangian transport equations for the velocity and the size/volume of a vast amount of cavitation nuclei. Mapping the nuclei on the Eulerian field determines the local vapor-volume fraction, which in turn is used to compute the fluid properties of the background flow in the Eulerian simulation. The animation shows an example of such hybrid simulation techniques for a cavitating NACA66mod-hydrofoil at the cavitation number σ=0.91, Re=2⋅106 and an angle of attack of α=4o.