Showing papers on "Rarefaction published in 1970"

Shock‐Wave Studies of PMMA, Fused Silica, and Sapphire

Abstract: The shock‐wave propagation characteristics of polymethyl methacrylate (PMMA), fused silica, and sapphire were measured for both compressive and rarefaction waves using plate‐impact experiments and interferometer instrumentation techniques The peak stress levels in the experiments were 22, 65, and 120 kbar, respectively The high‐resolution measurements of the stress wave profiles showed the PMMA to be a complex material whose wave propagation is influenced by nonlinearity, strain‐rate dependence, and elastic‐plastic effects in which plastic working increases the zero‐pressure volume of the material The fused silica is very well characterized as a nonlinear elastic material having the interesting property of propagating stable rarefaction shock waves The sapphire was nearly linear elastic to 120 kbar The use of these three transparent materials as ``windows'' in laser interferometer instrumented shock‐wave studies of other materials is discussed The effect of the shock‐induced variation of the index o

A note on ion rarefaction waves

Abstract: A theory is given of an ion rarefaction wave in a low pressure plasma under conditions where ionization processes are unimportant.

Some Characteristics of Exhaust Plume Rarefaction

Abstract: In this paper the rarefaction of a free jet expanding into a region of finite background pressure is considered It is found that the rarefaction process can be described by a simple rarefaction parameter D(P SP B^1^ / T Here D is the sonic orifice diameter, P8 is the reservoir pressure, PBW is the background pressure and T is the background and reservoir temperatures which are considered to be the same A simple scattering formulation of the complex physical problem is proposed Comparison of the scattering prediction and previous molecular beam flux measurements by Fenn and Anderson are presented A consistent physical description of a plume's approach to the limit of expansion into a perfect vacuum is discussed

Hugoniot and release‐adiabat measurements for selected geologic materials

Abstract: Release-adiabat curves have been determined for playa alluvium, tonalite, and novaculite shocked to stresses between 1 and 50 kb by plane impact from a light-gas gun. Particle-velocity/time profiles through the shock compression and the following release were measured at interfaces within the rock target and at the free surface using the principle of a moving conductor in a magnetic field. Steep release-adiabat curves in the stress-volume plane and high rarefaction velocities have been determined for alluvium and tonalite, indicating irreversible compaction. For alluvium, the initial rarefaction velocities are twice the shock velocities, which would cause rapid attenuation of the shock wave propagated in a field experiment. For novaculite, shocked below the Hugoniot elastic limit, the release-adiabat curve lies very close to the Hugoniot. The techniques should be applicable at higher stresses to study such problems as the kinetics of shock-induced phase changes.

Shock propagation into inhomogeneous media

Abstract: An analytic relation is derived for the shock front velocity as a function of the initial parameters (pressure, density, and particle velocity) in a continuous, in-homogeneous medium. This relation was verified experimentally by using it to predict the propagation of a shock wave through a known rarefaction wave.

Non-linear stable collisionless drift waves

Abstract: Analytic expressions have been found for the profile of non-linear stable drift waves in a collisionless anisothermal plasma, and also for the relationship of the wave velocity to the wave amplitude. It is shown that the nature of the nonlinear waves (compression or rarefaction) depends substantially on the type of electron distribution function. The wave amplitude is assumed to be small, but finite. For the distribution function closest to the Maxwellian, the nature of the wave is determined by the parameter ? = d ln T/d ln n.

Pressure wave propagation through annular and mist flows

Abstract: Pressure wave propagation through annular and mist flow patterns, noting virtual mass effects in interphase momentum transport of rarefaction and compression waves

Observational Confirmation of a Mechanism for the Production of Extended Stellar Atmospheres

Abstract: A recently reported mechanism for the production of extended stellar atmospheres is discussed in some detail and compared with presently available observations. The mechanism involves the outward acceleration of material in a rarefaction wave which follows the arrival of a shock wave at the edge of the atmosphere. It is shown that the rarefaction wave will generate a secondary shock wave of atmospheric origin as it moves back into the star. Observational evidence is cited for the existence of the secondary shock waves. The rarefaction waves also provide a mechanism for mass loss to the interstellar medium. An observational criterion is discussed for the existence of this mechanism and for distinguishing it from other mechanisms for mass loss.