Numerical simulation of cavitation erosion using coupled Euler-Lagrange models

该提案旨在开发和应用一种模拟空蚀的工程方法。调查是基于可压缩的Navier-Stokes方程的两相流的体积的流体制剂。空化模型是一个扩展的双向耦合欧拉-拉格朗日技术。大空化体积的分析将解决一个有效的气泡-气泡相互作用的修改。该计算方法模拟气泡动力学，根据Rayleigh-Plesset理论求解球形气泡/核的动量和体积的单个输运方程。现有的，验证并行欧拉-拉格朗日模型模拟复杂的不可压缩空化流将补充可压缩流模型。两个半经验的侵蚀模型，这是指不同的侵蚀机制，将追求，即一个建模的冲击压力引起的崩溃和反弹的球形气泡和替代的方法，该模型的微射流速度产生的非对称崩溃附近的材料表面。侵蚀和损坏风险的侵蚀性将通过建模和解析的压力水平、点蚀速率和点蚀直径进行量化。为了提高计算效率的水平，允许工程流模拟，现有的混合MPI/OpenMP并行算法将升级到多目标分区技术和镜像域的方法，广播的欧拉场的一部分全球的拉格朗日气泡的模拟。该程序将验证对单气泡配置，气泡流在简单的几何形状和实验研究准二维水翼的情况下的实验结果。最后的应用程序致力于螺旋桨流在后面的条件。

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.