Starting: April 2014
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.
Typical cavitation erosion damage on a compliant surface
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.
This project involves a collaboration between the laboratories LEGI, SIMAP and the University of Michigan through a long-term visitor grant.
1 Finite Element Method
2 Computational Fluid Dynamics
Yves Paquette, Christian Pellone, Marc Fivel, Giovanni Ghigliotti, Eric Johnsen and Jean-Pierre Franc. Modeling Fluid-Structure Interaction in Cavitation Erosion: Preliminary Results 2015, Journal of physics: Conference Series 656
PhD defense: 29th of november 2017
The project aims at developing a numerical model of fluid structure interaction including unsteady and compressible effects. The main objective is to predict the damage to the material due to cavitation erosion (pitting) and the more advanced phases (mass loss). To achieve this work three main stages are required: (1) development of an accurate numerical model of the highly unsteady collapse of a cavitation bubble near a wall taking into account the compressibility of both the fluid and the vapor phases and the subsequent development of shock waves; (2) computation of the unsteady responseof the material to the impact pressure load due to a collapsing cavitation bubble using a finite element model; (3) coupling of the two previous models to describe the fluid/structure interaction and provide a numerical tool for predicting cavitation erosion damage.