The structure of the Mach disk in supersonic free jets has been studied by using a static pressure probe. In the low density jets of post nozzle pressure less than 10 torr, the thickness of shock waves is affected by some upstream conditions, but the position of the termination is a function of the nozzle geometry and the pressure ratio as in an inviscid-continuum jet.
Relaxation problem of an initially nonequilibrium distribution toward the equilibrium distribution is studied using both the BOLTZMANN equation and the KROOK model. By the use of SONINE polynomial expansion method, distribution is determined from the non-linear BOLTZMANN equation for spatially uniform gases. By comparing the solutions of the KROOK model with those of the BOLTZMANN equation, it is shown that the KROOK model can not reproduce the correct distribution obtained from the BOLTZMANN equation for the case where departures from the equilibrium distribution are large. The KROOK model, however, can reproduce the correct distribution when the distribution approaches the equilibrium distribution.
The present paper is concerned with shockwave and viscous-layer structures ahead of a blunt body in a rarefied hypersonic flow. The analysis is within the framework of the continuum theory, based on the two-layer flow model. The solution for viscous layer is found to be matched with the solution for shock wave at the outer edge of viscous layer or at the downstream limit of shock wave. The profiles of flow variables, thus obtained, across the shock wave and viscous layer are found to be in a fairly good agreement with the results obtained, respectively, by LEVINSKY-YOSHIHARA and by KAO based on the method of full numerical integration for the NAVIER-STOKES equations. Furthermore some of characteristic features of the flow behavior due to rarefaction effects have been clarified by the analysis.