Shunxiang Cao

The collapse of a bubble near a solid material features a rapid, non-spherical compression of the internal gas, which may release mechanical and thermal energy in the forms of shock wave and liquid jet. This process, if carefully controlled, can be a unique approach for high-precision material modification and fabrication, and thus, has great potential in many engineering and biomedical applications. However, the multi-physics nature of the problem — featuring shock waves, multiphase flow, and material damage and fracture — has presented a fundamental challenge to the delicate control of the process. Thus, it calls for an improved understanding of the two-way coupling between bubble dynamics and the mechanical response of various materials.

This talk will focus on the recent efforts on modeling and simulating this kind of multi-physics problem, including the coupling of multiple materials and physical fields, and material damage and fracture under shock loads. A recently developed, three-dimensional fluid-solid coupled computational model, capable of simulating multi-bubble-material interaction and dynamic fracture, will be introduced. Specifically, the model couples a finite volume compressible flow solver with a nonlinear finite element solid mechanics (elasticity and viscoelasticity) solver using a partitioned procedure. The evolution of the bubble surface is captured by solving the level set equation and the surface of solid material is represented as a dynamic embedded boundary in the flow solver. The interface conditions are enforced through the construction and solution of local fluid-solid and two-fluid Riemann problems. The material damage and fracture are modeled and simulated using a continuum damage mechanics model and an element erosion method. Several numerical studies in the context of lithotripsy will be presented to demonstrate the capability of the model in capturing the two-way coupling between cavitation bubble dynamics and the dynamic response and failure of various solid and soft materials.

Biography:

Dr. Shunxiang Cao received his bachelor’s degree in Aerospace Engineering from Beihang University in 2014. He joined the graduate program in the Department of Aerospace and Ocean Engineering at Virginia Tech in 2014, and received a Ph.D. degree in Aerospace Engineering in 2019. He is now a post-doctoral scholar in the Department of Mechanical and Civil Engineering at the California Institute of Technology. His research mainly focuses on the numerical simulation of complex fluid-structure interaction (FSI) problems, including the development of high-performance computational methods and the modeling of multi-physical effects (e.g., multiphase flow, shock wave, material damage and fracture). He is currently working on developing numerical tools for studying urinary stone treatment using Shock/Burst Wave Lithotripsy.