The Shape and Thickness of Shock Fronts in Argon, Hydrogen, Nitrogen, and Oxygen

Abstract

Measurements-of shock front thicknesses in argon by the reflectivity method have been extended to Mach 2.09, and the shape of the front has been investigated by comparing the experimental results with the reflectivity expected on the basis of five simple models for the density change through the front. The thicknesses agree with Zoller's calculations but for the strongest shocks are considerably greater than those of other ~eoretical.estim~tes. The magnitude and form of the reflectivity (as a function of XIL cos8) of shock fronts In three diatomIc gases have been used to study the rate of equilibration of rotational with translational energy. Hydrogen requires more than one hundred and fifty collisions for this equilibration while nitrogen and oxygen equilibrate much more rapidly. For the latter two gases there is evidence that at least two relaxation times are involved in the equilibration. 9 A.

An axisymmetric computational model of generalized hydrodynamic theory for rarefied multi-species gas flows

“…Compared with the N-S and monatomic GH results, the diatomic GH equations provide the closest result to many experimental data [30][31][32][33][34] as well as the DSMC result [35]. In addition, the present GH result agrees well with the computation by Al-Ghoul et al [36,37].…”

“…In many cases, the potential parameter D e can be experimentally obtained. [30]; ð4Þ by Linzer and Hornig [31]; ð.Þ by Camac [32]; ð}Þ by Robben and Talbot [33]; ðÞ by Alsmyer [34]. ðÃÞ represents the DSMC result by Boyd [35].…”

A generalized hydrodynamic computational model for rarefied and microscale diatomic gas flows

“…The flow conditions are; M ¼ 5:48, Kn ¼ 0:05, T w ¼ 293 K, T 1 ¼ 26:6 K. As the first test case, a monatomic [21]; (n) by Linzer and Hornig [22]; (x) by Camac [10]; (Â) by Robben and Talbot [29]; and (s) by Alsmyer [3]. The squares (Ã) represent the results calculated by DSMC theory [8].…”

“…For artificial boundaries, inflow and outflow conditions based on the number of Euler characteristics can be employed. The discretized form of the generalized hydrodynamic equations in the finite volume formulation (29), a time step restriction (40), and the boundary conditions (21) and (22) are the basic building blocks of the present numerical method. It resembles numerical methods for the compressible Navier-Stokes equations in that they all share the hyperbolic conservation laws.…”

Experiments on Non-Equilibrium Supersonic Flow Shock Stand-Off Distance of Spheres Carried Out in a New Type of Intermittent Wind Tunnel

“…The apparent shock thickness is approximately 0.002 cm. The actual thickness of the shock wave as determined from experiments in nitrogen at room temperature and pressure and at M = 1.4 is approximately 6 x 10 -5 cm (52) and is negligible with respect to the apparent thickness of the shock wave. The apparent shock thickness cannot be decreased further by focusing closer to the centerline since the shock image of the 1/52 in.…”