Becker–Morduchow–Libby solution

The Becker–Morduchow–Libby solution is a mathematical description of how the properties of a gas—such as pressure, temperature, and density—change within a one-dimensional shock wave. It is an exact solution of the Navier–Stokes equations for a compressible, viscous, heat-conducting gas. First derived in a simplified form by German physicist Richard Becker in 1922, it was later extended by Morris Morduchow and Paul A. Libby in 1949. Independent versions were also found in 1944 by M. Roy and L. H. Thomas. The solution revealed an unexpected feature: the entropy of the gas can vary in a non-monotonic way across the shock, rather than increasing steadily. Earlier work by Lord Rayleigh and G. I. Taylor had addressed special cases, such as flows with viscosity but no heat conduction, or vice versa.