Numerical Investigation of Shock Instabilities in Noble Gases

Speaker: Michael Kapper, Austrian Space Research Institute
November 3, 2016

Presentation

Abstract

A series of shock tube experiments performed in the 70’s at the Institute for Aerospace Studies, University of Toronto, resulted in the discovery that un-der hypervelocity conditions, the translational shock front propagating in pure Argon “develops sinusoidal instabilities which aﬀect the entire shock structure including the ionization relaxation region, the electron cascade front, and the final quasi-equilibrium state”. Theoretical models were ﬁrst developed in order to reproduce the length and time scales of the observed quasi-equilibrium state, and later extended to include plasmadynamic simula-tions that veriﬁed the inﬂuence of pressure oscillations in one dimension. Despite these attempts, a complete explanation for the oscillations nor a quan-titative analysis of the multi-dimensional shock structurehas previously been provided. Through the use of direct simulation we provide theﬁrstdetails of the multi-dimensional shock structure which corroborate the experimental results. The numerical capability is built around a 3rd-order algorithm for solving the transport equations of plasma under highly non-equilibriumconditions. The plasma is described as a two-temperature, single ﬂuid with the kinetics of col-lisional and radiative excitation and ionization, and reverse processes. Recent extensions of the models including MHD eﬀects will also be highlighted.

Biography

With a background in chemistry and mechanical engineering, Michael Kapper’s main interests lie in the development of Riemann solvers for high-enthalpy gas and plasma transport coupled with ﬁnite-rate chemical and ionization kinetics. The presented work is based on research he conducted while at the Air Force Re-search Laboratory, Edwards Air Force Base. Subsequent research at the von Karmann Institute for Fluid Dynamics led to investigation of rareﬁed ﬂows through the Regularized 13-moment equations. After antenna calibration for the Solar Orbiter and JUICE missions while at the Austrian Space Research Institute, he has since returned to plasma transport phenomena.

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