Fluid-structure interaction in cavitation erosion

When a fluid is submitted to rapid changes of pressure, the strong forces acting upon the liquid lead to the formation of vapour cavities. This phenomenon, known as cavitation, generates intense shockwaves through repeated implosion, and has important negative effects on machines efficiency or material surfaces. But cavitation can also find some interesting applications, especially in therapeutic ultrasound techniques where it is used for soft tissues ablation or the destruction of kidney stones.

This project aims at studying, in a dynamic way, the fluid–structure interactions under cavitating configurations, in order to better understand the phenomenon and provide numerical tools for the simulation of complex aggressive cavitating flows.

The approach followed in the project consists in a three steps “model coupling strategy” addressing the questions of the fluid’s behaviour during a cavitation event, the response of the solid material to the forces exerted by the cavitating fluid, and the feedback effects of the solid deformation on the fluid’s behaviour. A fluid numerical model taking into account viscous stresses and heat transfer parameters is being developed to address the unsteady and compressible effects occurring in both liquid and vapor water, and to finely describe the dynamics of a bubble collapsing near a wall.
 
A material numerical model will then be developed using the FEM¹ approach included in the code CAST3M developed by the CEA, to investigate the unsteady response of the material to the forces exerted by a single cavitation impact calculated by the fluid model. In a second time, the model will be refined to take into account repetitive impacts.
 
Finally, a dynamical fluid-structure interaction model will be developed to simulate the way that solid surface deformation modifies the bubble’s behaviour and the nearby pressure field. The method will consist in coupling the CFD² and FEM codes by an iterative procedure with the use of a Python script.
 
1 Finite Element Method
2 Computational Fluid Dynamics