EC Rericha, C Bizon, MD Shattuck, HL Swinney, Shocks in Supersonic Sand, Phys. Rev. Lett. 88(1):014302(4) 2002. PMID:11800951. [Citations: 71]. [pdf]
We measure time-averaged velocity, density, and temperature fields for steady granular flow past a wedge. We find the flow to be supersonic with a speed of granular pressure disturbances (sound speed) equal to about 10% of the flow speed, and we observe shocks nearly identical to those in a supersonic gas. Molecular dynamics simulations of Newton's laws yield fields in quantitative agreement with experiment. A numerical solution of Navier-Stokes-like equations agrees with a molecular dynamics simulation for experimental conditions excluding wall friction.