Multi-component cavitation modelling for the numerical flow simulation of real fluid mixtures in hydraulic systems

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In hydraulic systems, usually complex fluid mixtures e.g. hydraulic oils or fuels are utilized. These mixtures consist of several hundred distinct components whose fluid and transport properties depend on the local mixture composition. It is assumed that for bubble dynamics and cavitation, in dependence on environmental conditions around the bubble, a local fuel segregation of the light and heavy volatile components within as well as around the bubble occurs, similar to droplet evaporation. Recent CFD methods use cavitation models that do not account for this segregation. Therefore, they reflect the occurrence of cavitation e.g. in fuels only insufficiently. The aim of the proposed project is the development of a multi component single bubble dynamics model that describes the heat and mass transfer as well phase change of spherical bubbles component-wise and therefore captures the fluid mixture segregation. Simple fluid mixtures are treated with a discrete model and real mixtures as e.g. fuels by a multi component model based on continuous thermodynamics. Furthermore, the interaction between air release and absorption with cavitation in multi-component fluid mixtures is modelled. The validation and application is performed on test cases which are representative for injection and oil hydraulic systems. In a first step, even the application of the multi-component single bubble model serves for a better understanding of the cause and effect chain between fluid mixture, bubble dynamics, air release and cavitation erosion. In a second step, it is aimed at a subsequent project with the focus on multi component cavitation modelling for 3D CFD.