Numerical simulation of cavitation erosion using coupled Euler-Lagrange models

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The proposal aims at the development and application of an engineering approach to simulate cavitation erosion. The investigations are based on the compressible Navier-Stokes equations for two-phase flows in a volume-of-fluid formulation. The cavitation model refers to an extended two-way coupled Euler-Lagrange technique. The analysis of large cavitating volumes will be addressed by an efficient bubble-bubble interaction modification. The computational method mimics the bubble dynamics solving individual transport equations for the momentum and volume of spherical bubble/nuclei according to the Rayleigh-Plesset theory. An existing, validated parallel Euler-Lagrange model for the simulation of complex incompressible cavitating flows will be supplemented by a compressible flow model. Two semi-empirical erosion models, which refer to different erosion mechanisms will be pursued, i.e. one modeling the impact pressure induced by the collapse and rebound of a spherical bubble and an alternative approach which models the micro-jet velocity generated from a non-symmetric collapse near the material surface. Aggressiveness of the erosion and damage risks will be quantified by means of modeled and resolved pressure levels, pitting rates and pitting diameters. In order enhance the computational efficiency to a level that permits engineering flow simulations, an existing hybrid MPI/OpenMP parallel algorithm will be upgraded towards multi-objective partitioning techniques and mirror-domain approaches, that broadcast part of the Eulerian field globally to the simulation of the Lagrangian bubbles. The procedure will be validated against experimental results for single-bubble configurations, bubble streams in simple geometries and experimentally investigated quasi-two-dimensional hydrofoil cases. Final applications are devoted to propeller flows in behind conditions.