Rarefaction

About: Rarefaction is a research topic. Over the lifetime, 1852 publications have been published within this topic receiving 26943 citations.

The asymptotic behaviors of solutions to the perturbed Riemann problem near the singular curve for the chromatography system

Abstract: The Riemann problem for a simplified chromatography system is considered and the global Riemann solutions are constructed in all kinds of situations. In particular, the zero rarefaction wave, the zero shock wave and the zero delta shock wave are discovered in the Riemann solutions in some limit situations, which have infinite propagation speeds. Furthermore, these zero waves are analyzed by introducing the so-called double Riemann problem with three pieces of constant states. More precisely, we take the approximations of zero waves and investigate wave interactions in details before the limits are taken.

Reshocks, rarefactions, and the generalized Layzer model for hydrodynamic instabilities

Abstract: We report numerical simulations and analytic modeling of shock tube experiments on Rayleigh–Taylor and Richtmyer–Meshkov instabilities. We examine single interfaces of the type A/B where the incident shock is initiated in A and the transmitted shock proceeds into B. Examples are He/air and air/He. In addition, we study finite-thickness or double-interface A/B/A configurations such as air/SF6/air gas-curtain experiments. We first consider conventional shock tubes that have a “fixed” boundary: A solid endwall which reflects the transmitted shock and reshocks the interface(s). Then we focus on new experiments with a “free” boundary—a membrane disrupted mechanically or by the transmitted shock, sending back a rarefaction toward the interface(s). Complex acceleration histories are achieved, relevant for inertial confinement fusion implosions. We compare our simulation results with a generalized Layzer model for two fluids with time-dependent densities and derive a new freeze-out condition whereby accelerating ...

Numerical simulation of shock wave and contact surface propagation in micro shock tubes

Abstract: Micro shock tubes have been widely used in many engineering and industrial applications, but their performance and detailed flow characteristics are not well known. Compared to macro shock tubes, unsteady flows related to the moving shock waves in micro shock tubes are highly complicated due to more active viscous dissipation and rarefaction effects. This makes shock wave dynamics significantly different from theoretical predictions. One of the major flow behaviors related to the shock wave propagation in micro shock tube is that the boundary layer growth leads to stronger dissipative shock wave. Due to effects of the scale, more shock wave attenuation happens in micro shock tubes. We used a CFD approach to understand the flow characteristics in a micro shock tube with finite diameter. A fully implicit finite volume scheme has been employed to solve the unsteady compressible Navier-Stokes equations. The diaphragm pressure ratio and diameter of the shock tube were varied to investigate their effects on micro shock tube flows. Based on the predicted results, some wave diagrams were built to characterize the micro shock tube flows. Detailed flow structures between the contact surface and moving shock wave were analyzed during the present study.