Three-dimensional flow simulation and cavitation erosion modeling for the assessment of incubation time and erosion rate

Abstract

A compressible three-dimensional in-house flow solver is employed for the assessment of cavitation erosion. The flow solution method provides the wall load, which is coupled to a one-dimensional ductile material model and which yields the incubation time and erosion rate. Due to the assumption of a homogeneous mixture in the flow solver, details of collapsing wall adjacent single bubbles cannot be resolved, so that two different wall load models are presented. In the first method, a collapse detection algorithm based on the mass flux divergence is applied, load collectives are statistically evaluated by the multitude of detected collapses, and a spectrum of distinct loads is passed on to the material model. Since the physical simulation time is much shorter than the real exposure time, a method for the time extrapolation of the wall load to capture realistic time scales is presented. In the second method, a sub grid scale micro jet model is applied, and the wall load is approximated by mean values, so that a time extrapolation is dispensable. Both methods require calibration to e.g. experimentally measured incubation time. An application to the widely used Grenoble axisymmetric impinging jet test case reveals, that the first method fails to capture the location of maximum wear. Due to the inclusion of an erosion probability for the detection of prospectively erosive collapse events in the second method, a good match with data is obtained. Beyond a validation for a broad range of erosive flow conditions, the use of alternative material models including high cycle fatigue as important wear mechanism is planned in future studies.