Nonequilibrium Molecular Motion in a Hypersonic Shock Wave

Abstract

Molecular velocities have been measured inside a hypersonic, normal shock wave, where the gas experiences rapid changes in its macroscopic properties. As first hypothesized by Mott-Smith, but never directly observed, the molecular velocity distribution exhibits a qualitatively bimodal character that is derived from the distribution functions on either side of the shock. Quantitatively correct forms of the molecular velocity distribution function in highly nonequilibrium flows can be calculated, by means of the Direct Simulation Monte Carlo technique.

Experimental and numerical investigation of an axisymmetric supersonic jet

“…The dynamics of normal shock waves, similar to the Mach disk of supersonic jets, has been widely studied in one dimension, theoretically (Mott-Smith 1951), numerically (Koura 1997) using the direct simulation Monte Carlo method (DSMC) developed by Bird (1994), and experimentally (Robben & Talbot 1966a, b;Alsmeyer 1976;Pham-Van-Diep, Erwin & Muntz 1989).…”

Atomistic phenomena in dense fluid shock waves

“…This overshoot was first predicted theoretically [25,26], but later confirmed experimentally (Ref. [27] is a more recent example).…”

To Extend the Thirteen-Moment Theory and Its Application to Problems in Rarefied Hypersonic Flow

“…[26] and discussed also in Ref [12] for a plane normal shock. An important feature brought out by our DSMC calculations in the course of the present study is the surprisingly early decay of this spiky bimodal-like feature towards the downstream end where most macroscopic properties, such as density, velocity, and temperature, have not quite reach their respective downstream/terminal values.…”

“…The work was motivated by the pronounced spiky feature brought out in Ref. [26], reminiscent of the Mott-Smith's bimodai dsitribution [29], which is not describable by solution to the 13-moment equations in Grad's original form. It is essential to point out that the additional moments are introduced here not as a straightforward improvement of Grad's liermite-polynomial expansion of the distribution function "f".…”

“…----- familiar from experiment and DSNIC analyses [26], which signifies the persistence of the upstream influence. The discrepancy near the wall may be related to the cold-wall anomaly mentioned, although negaIiv.,e values in ]J and fl, are not found.…”