Title: Still water: ejecta from granular jet impact is generic

Author (Poster): Jake Ellowitz, James Franck Institute

Abstract:

when a high-density jet of grains hits a target it surprisingly ejects particles in a thin sheet quantitatively similar to water bells created by liquid-jet impact. Our experiments, simulations and continuum modeling show that such ejecta sheets are generic and independent of the jet's internal structure, be it a static zone as in the granular jet, freely flowing as in a low viscosity fluid, or a wedge-shaped target. The thin sheet formation and its ejection angle are consequences of the dense jet behaving as a perfect fluid. In contrast with the expectation that scattering provides sufficient information to reconstruct the internal state, the macroscopic observables, e.g., thin-sheet ejection angle, give little information about the jet dynamics when the density is high. The creation of a static zone by impact alone, without cohesive forces, sheds light on collision-induced accretion, a process important for planetesimal formation. Moreover, our analysis challenges the association of a Newtonian viscosity with the scattering patterns of the quark-gluon plasma at the Relativistic Heavy Ion Collider.