Rarefaction

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

The New Wave in Shock Waves

Abstract: Laser-driven shock waves (0−5 GPa) can be generated at high repetition rates (100/s) using a moderate-energy tabletop picosecond laser system and a multilayered microfabricated shock target array. High spatial resolution is needed to obtain high temporal resolution of the effects of a steeply rising shock front on molecular materials. The needed spatial resolution is obtained using a sandwich arrangement with a thin layer of sample material termed an “optical nanogauge”. Experiments with an anthracene nanogauge show that ultrafast vibrational spectroscopy can be used to determine the shock temperature, pressure, velocity, and shock front rise time. Shock pulses can be generated with rise times <25 ps, which generate irreversible shock compression, and with rise times of a few hundred picoseconds, which generate reversible compression. These pulses, which have a duration of a few nanoseconds, are termed “nanoshock” pulses. Nanoshock pulses produce large-amplitude mechanical perturbations and can initiate a...

A comparative numerical study of the Richtmyer-Meshkov instability with nonlinear analysis in two and three dimensions

Abstract: A shock driven inter-facial instability, known as the Richtmyer-Meshkov instability, is studied numerically in two and three dimensions and in the nonlinear regime. The numerical solution is tested for convergence under computational mesh refinement and is compared with the predictions of a recently developed nonlinear theory based on the Pade approximation and asymptotic matching. Good agreement has been found between numerical solutions and predictions of the nonlinear theory in both two and three dimensions and for both the reflected shock and the reflected rarefaction wave cases. The numerical study is extended to the re-shock experiment in which the fluid interface interacts initially with the incident shock. Later, as the transmitted shock bounces back from the wall, the fluid interface is re-shocked.

Asymptotics toward the planar rarefaction wave for viscous conservation law in two space dimensions

Abstract: This paper is concerned with the asymptotic behavior of the solution toward the planar rarefaction wave r( t ) connecting u+ and u− for the scalar viscous conservation law in two space dimensions. We assume that the initial data u0(x, y) tends to constant states u± as x → ±∞, respectively. Then, the convergence rate to r( t ) of the solution u(t, x, y) is investigated without the smallness conditions of |u+−u−| and the initial disturbance. The proof is given by elementary L2-energy method.

Experimental Analysis of Pressure Drop and Laminar-to-Turbulent Transition for Gas Flows in Smooth Microtubes

Abstract: The results of numerical and experimental works dealing with the behavior of gas flow through microchannels are by no means univocal, sometimes agreeing with the classical correlations and other times contradicting them. It is now agreed upon that the effects due to both rarefaction and compressibility must be accounted for. In addition, the experimental works have demonstrated that sometimes compressibility and rarefaction effects can be coupled in microchannels: because these two actions contrast each other, the scatter of the friction factor data for gaseous flows is remarkably large. This paper is aimed at determining the friction factor for commercial short and long Peek microtubes with nominal internal diameters between 300 and 100 μ m and values of the length-to-diameter ratio, L/D, ranging between 167 and 5000. Nitrogen flows inside the microtubes, with a maximum value of the supply pressure equal to 10 bar. Very low Knudsen numbers (Kn < 0.001) are considered in order to uncouple the rarefaction ...

Effects of solar flare duration on a double shock pair at 1 au.

Abstract: Numerical solutions of the time-dependent equations of motion for spherically symmetric flow are obtained to study the propagation and modification of the forward-reverse shock pair in the region between the sun and 1 AU. For cases where the duration of the disturbance is long compared to T, the shock transit time to 1 AU, a double shock pair that resembles those predicted by similarity theory occurs at 1 AU. In cases where the duration of the solar disturbance is less than about 0.45T, the shock pair structure is appreciably altered by a rarefaction, initiated at the end of the solar disturbance, which has caught up with the shock pair. In cases where the duration is less than about 0.1T, the rarefaction completely destroys the reverse shock, leaving a single shock. This analysis indicates that a forward-reverse shock pair will not be observed at 1 AU unless the time duration of the solar disturbance is greater than about 5 hours. Since solar flares that last this long are quite rare, it is concluded that observation of a flare-associated forward-reverse shock pair at 1 AU is unlikely.