Micro-jetting from a triangular groove: Comparison of ejecta source models based on nonlinear Richtmyer-Meshkov instabilities and oblique shock waves

We compare two different approaches to calculate the jet velocity and areal density of matter ejected after the reflection of a shockwave on a triangular groove, located at the free surface of a metal sample. The first (historical) one is based on nonlinear Richtmyer-Meshkov instabilities (RMI's), and the second one combines two models that were recently developed at CEA, BMPT-2, on the one hand, for the calculation of the velocity and density of the jet, and Fragmentation Zone Propagation (FZP), on the other hand, for the calculation of the ejected areal mass. Some of the parameters required by FZP are calculated directly from BMPT-2. We show that they are two complementary approaches. Whereas RMI's can provide a cumulated areal ejected mass, i.e. a scalar, independently of the fragmentation process involved, BMPT-2 + FZP allow to deal with the distribution of the ejected mass and final size of the particles, as a function of their velocity, based on a given fragmentation process. Nevertheless, they may fail to assess the total ejected mass, due to the difficulty to model completely the fragmentation of the jet, up to the free surface. Combining these two approaches could be of interest to estimate both the total ejected mass and the way it spreads ahead of the free surface.