Article

Giant wall shear stress from cavitation bubble collapse

* Presenting author
Day / Time: 20.03.2018, 15:00-15:20
Room: MW 0250
Typ: Regulärer Vortrag
Abstract: The collapse of a cavitation bubble near a rigid boundary induces a high-speed transient jet accelerating liquid onto the boundary. The shear flow produced by this event has many applications, examples are surface cleaning, cell membrane poration, and enhanced cooling. Yet the magnitude and spatio-temporal distribution of the wall shear stress are not well understood, neither experimentally nor by simulations. Here we solve the flow in the boundary layer using an axisymmetric compressible Volume of Fluid (VOF) solver from the OpenFOAM framework and discuss the resulting wall shear stress generated for two cases of the non-dimensional distance, γ=1 and γ=0.85 (γ=h/Rmax, where h is the distance of the initial bubble centre to the boundary, Rmax the maximum spherical equivalent radius of the bubble). Very high wall shear stresses of 10kPa and more are found during the early spreading of the jet followed by complex flows composed of annular stagnation rings. Although the simulated bubble dynamics is agreeing very well with experiments we obtain only qualitative agreement with experiments due to inherent experimental challenges.