Relevance of the Fragmentation Zone Propagation model issued from molecular dynamics simulations to interpret photo Doppler velocimetry measurements in microjetting experiments.

We recently proposed a model of fragmentation of ejected sheets of liquid metal issued from shock-loaded surfaces (microjetting). This model, called Fragmentation Zone Propagation (FZP), results from the analysis of very large-scale Molecular Dynamics (MD) simulations of the phenomenon. We tested its relevance by performing shock-induced experiments of matter ejection on grooved tin samples. We analyzed in particular the behavior of the ejecta cloud using a photon Doppler velocimetry (PDV) setup. We show that, although the FZP model results from simulations performed at much smaller length scales than those of experiments, it may be very helpful to interpret the experiments. In particular, it predicts that the ejecta are not created at the same time in the cloud: they are created first near the tip of the sheets. Then the fragmentation zone, where the ejecta are created, counter-propagates in the sheet towards the free surface. This is what we observe in our PDV measurements.