Mass-Stripping Analysis of an Interstellar Cloud by a Supernova Shock

The interaction of supernova shocks and interstellar clouds is an important astrophysical phenomenon since it can result in stellar and planetary formation. Our experiments attempt to simulate this mass-loading as it occurs when a shock passes through interstellar clouds. We drive a strong shock using the Omega laser (∼5kJ)into a foam-filled cylinder with an embedded Al sphere(diameterD=120 μm) simulating an interstellar cloud. The density ratio between Al and foamis∼9. We have previously reported on the interaction between shock and cloud, the ensuing Kelvin-Helmholtz and Widnall instabilities, and the rapid stripping of all mass from the cloud. We now present a theory that explains the rapid mass-stripping. The theory combines (1) the integral momentum equations for a viscous boundary layer, (2) the equations for a potential flow past a sphere, (3) Spalding's law of the wall for turbulent boundary layers, and (4) the skin friction coefficient for a turbulent boundary layer on a flat plate. The theory gives as its final result the mass stripped from a sphere in a turbulent high Reynolds number flow, and it agrees very well with our experimental observations.