Topic
Rarefaction
About: Rarefaction is a research topic. Over the lifetime, 1852 publications have been published within this topic receiving 26943 citations.
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TL;DR: In this paper, the authors studied the unsteady motion of a rarefied gas between two parallel plates, one of which is oscillating in its plane, based on the linearized Boltzmann equation for a hard sphere molecular gas.
17 citations
TL;DR: In this paper, the random choice method (RCM) was used to calculate non-linear wave propagation in gas-vapour-droplets mixtures, and the theoretical model of heterogeneous nucleation and droplet growth was discussed.
17 citations
TL;DR: In this paper, a simple reconstruction algorithm based on the advection-diffusion equation has been developed to obtain the velocity profile from the displacement field, in spite of the non-equilibrium state of the background gas.
Abstract: The molecular tagging velocimetry (MTV) is a well-suited technique for velocity field measurement in gas flows. Typically, a line is tagged by a laser beam within the gas flow seeded with light emitting acetone molecules. Positions of the luminescent molecules are then observed at successive times and the velocity field is deduced from the analysis of the tagged line displacement and deformation. However, the displacement evolution is expected to be affected by molecular diffusion, when the gas is rarefied. Therefore, there is no direct and simple relationship between the velocity field and the measured displacement of the initial tagged line. This paper addresses the study of tracer molecules diffusion through a background gas flowing in a channel delimited by planar walls. Tracer and background species are supposed to be governed by a system of coupled Boltzmann equations, numerically solved by the direct simulation Monte Carlo (DSMC) method. Simulations confirm that the diffusion of tracer species becomes significant as the degree of rarefaction of the gas flow increases. It is shown that a simple advection–diffusion equation provides an accurate description of tracer molecules behavior, in spite of the non-equilibrium state of the background gas. A simple reconstruction algorithm based on the advection–diffusion equation has been developed to obtain the velocity profile from the displacement field. This reconstruction algorithm has been numerically tested on DSMC generated data. Results help estimating an upper bound on the flow rarefaction degree, above which MTV measurements might become problematic.
16 citations
TL;DR: In this article, the authors developed a physical model to describe the pore collapse, crack expansion, and hot spot formation mechanisms and calculate a set of key parameters, such as pore collapsing speed, rarefaction wave speed, and crack expansion speed.
Abstract: We simulate the shock loading process of β-octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine by molecular dynamics and calculate the isoentropic curve, Hugoniot curve, temperature field, velocity field, stress field, and density field. Based on the simulation results, we develop a physical model to describe the pore collapse, crack expansion, and hot spot formation mechanisms and calculate a set of key parameters, such as pore collapsing speed, rarefaction wave speed, and crack expansion speed. A microscopic physical picture for defect evolution at the early time of shock loading is obtained.
16 citations
TL;DR: In this article, the formation and propagation of shock waves in a two-component flowing bubbly mixture has been investigated experimentally and the structure of the shock wave formed by steepening of compression waves is compared with the corresponding features of shocks produced spontaneously in shock tubes.
16 citations