Multi-Component Cavitation Modeling for Numerical Flow Simulation of Real Fluid Mixtures in Hydraulic Systems

Project duration: 2017-2021
Financing: Deutsche Forschungsgemeinschaft (DFG)

In hydraulic systems, complex fluid mixtures such as hydraulic oils or fuels are typically used. These mixtures can consist of up to several hundred individual components, whose properties and transport characteristics depend on the local composition of the mixture. It is hypothesized that, similar to fuel droplet evaporation, there is local fuel segregation (demixing) of the low- and high-boiling components within and around the bubble, depending on the environmental conditions of the bubble, in the context of bubble dynamics and cavitation. Currently available cavitation models in CFD methods neglect these demixing processes and inadequately represent the appearance of cavitation in fuels, for example.

Building on available bubble dynamic models for single-component fluids, a multi-component single-bubble model for spherical bubbles will be developed. This model will describe heat, mass, and phase transitions component-wise, and thus fluid mixture segregation. Simple fluid mixtures will be described discretely, while real fluids, such as fuels, will be described using continuous thermodynamics. Furthermore, the interaction of air outgassing and air absorption with cavitation in multi-component mixtures will be modeled. Validation and application will occur in flow test cases representative of injection systems and oil-hydraulic components. 

The application of the multi-component single-bubble model will already contribute to a better understanding of the interactions between fluid mixtures, bubble dynamics, air outgassing, and cavitation erosion. This model will also lay the foundation for the development of multi-component cavitation models in 3D CFD methods, which will be examined in a subsequent planned project.

Contact: Philip Schwarz