The Richtmyer-Meshkov Instability

　　题目: The Richtmyer-Meshkov Instability

　　报告人：Ravi Samtaney (King Abdullah University of Science and Technology)

　　时间：　 2013年9月12日 下午3:00

　　地点：　 力学一楼239

Ravi Samtaney简介：

　　Ravi Samtaney is presently an associate professor in Mechanical Engineering (Physical Science and Engineering Division) with a joint appointment in Applied Mathematics at the King Abdullah University of Science and Technology (KAUST) in the Kingdom of Saudi Arabia. Prior to KAUST, he was a Research Physicist at the Princeton Plasma Physics Laboratory, Princeton University. He has also held research positions at NASA Ames Research Center and the California Institute of Technology. His research is at the intersection of applied mathematics, physics, and engineering, from fundamental processes in fluid mechanics, magneto-hydrodynamics to numerical methods and high-performance computing. He obtained his PhD under the supervision of Professor Norman Zabusky from Rutgers University in 1994.

Abstract:

　　The Richtmyer-Meshkov instability (RMI) arises in fluids when an interface is impulsively accelerated, usually by a shock wave. This instability is observed in nature (e.g. astrophysics in which a supernova blast wave accelerates surrounding interstellar medium) although RMI has been mostly motivated by inertial confinement fusion (ICF) in which it plays a rather detrimental role.  In this talk, we first review the history of the instability. We present a vortex dynamical viewpoint originally espoused by Zabusky and Hawley (Phys. Rev. Lett. 1989) in which the baroclinic generation of vorticity at the fluid interface is shown as the primary driving mechanism of the instability.  Furthermore, we present scaling laws for the baroclinic vorticity based on asymptotic analysis of shock refraction theory.  More recently it has shown that the presence of a magnetic field suppresses the instability. This is due to a bifurcation in which the vorticity is transported away from the interface, usually by slow-mode shocks. Finally, we shed some light on a couple of mathematical curiosities: one of these is related to the ill-posedness of the Euler equations and the other to the singular limit of the MHD equation to hydrodynamics as the magnetic field strength tends to zero.