In hydraulic systems, fluid mixtures e.g., hydraulic oils or fuels are utilized. These mixtures consist of several distinct components whose fluid and transport properties depend on the local mixture composition. In preliminary work it was shown by 1D CFD simulations on spherical single bubbles that for bubble dynamics additionally to air release, a local fuel segregation of the light- and heavy-volatile components within as well as around the bubble occurs, similar to droplet evaporation. This segregation is most pronounced in the presence of a high amount of heavy-volatile species and considerably effects bubble growth, which was traced back to species interdiffusion and its effect on evaporation mass and latent heat flux. By a first version of a 3D method assuming a homogeneous mixture, local segregation was also observed on a high-pressure fuel injector. For this 3D method, sub grid scale models for local species interdiffusion and cavitation-induced air release will be developed in this project proposal. Therefore, considering all transport processes and first order principles, the mathematical model of the 1D single bubble method will be adopted to a phase interface resolving 3D volume-of-fluid method and applied to bubble clusters. From these bubble cluster reference results, sub grid scale models will be derived, integrated into the homogenous mixture approach and validated on a planar diffuser as well as high pressure injector, including primary breakup. The resulting 3D multi component cavitation model enables a considerably more accurate simulation of cavitating flow in fluid mixtures, than is feasible with recent single-component surrogate fluids.
DFG Programme
Research Grants
