MD-CFD Hybrid Simulation for Microbubble Dynamics

We have developed a hybrid numerical simulation code to investigate the dynamics of nanobubbles. The idea is based on a combination of a molecular dynamics (MD) technique for the region containing a bubble and surrounding area, and the lattice Boltzmann method (LBM) for the region well away from the bubble. The boundary between the two regions is movable and driven by their pressure difference. As a test of the developed code, we have performed a simulation of a collapsing nanobubble. After equilibrating the system, we introduce a uniaxial pressure wave in the continuum region far from the bubble. The pressure wave propagates through the LBM region, and the pressure difference deforms the MD-LBM boundary. As the MD region deforms, the bubble inside the region starts to collapse non-spherically. We have analyzed the bubble collapse dynamics with several different pressure waves. Vapor bubbles and bubbles containing noncondensable particles are compared.