Numerical Prediction Approach of Cavitation Erosion based on 3D Simulation Flow

Abstract

In industry, the phenomenon of cavitation erosion can reduce the lifetime of the components of hydraulic machines. In this article, we present a new numerical approach to predict the mechanical impact resulting from the implosion of a cloud of bubbles, based on an energy approach. The objective of this approach is to determine the main damage mechanisms and to estimate the intensity of the impact pressure near the surface. The large eddy simulation (LES) approach is coupled with a homogeneous cavitation model to assess the risk of erosion around the hydrofoil NACA0009. Indeed, three functions, namely the Pressure Intensity Function (PIF), the steam intensity function and the Erosive Power Function (EPF), are applied to assess the spatial distribution of eroded areas. The calculations show that the functions based on the pressure term are in good agreement with the experiments, namely: the PIF and EPF functions. On the other hand, we assume that the implosion of the cloud of bubbles produces a pressure wave, which in turn causes the implosion of small bubbles near the wall. Then the erosion will be the result of these secondary implosions and not of the cloud of bubbles. Therefore, we vary the degree of proximity of these micro-bubbles near the wall to choose either the shock wave or the micro-jet to extrapolate the pressure field. We can compare these estimates with the existing erosion measurements and we can conclude that the calculations respond more to the probability of the presence of a micro-jet than to the presence of a shock wave.