Rarefaction

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

Asymptotics toward rarefaction wave of solutions of the Broadwell model of a discrete velocity gas

Abstract: This paper studies the asymptotic behavior toward rarefaction wave for solutions of the initial value problem to the one-dimensional Broadwell model of the Boltzmann equation. When the Riemann problem for the Euler equation, derived from the Chapman-Enskog expansion, admits the solution of weak rarefaction wave, we also call the corresponding local Maxwellian of the original Broadwell model “rarefaction wave”. Then if the initial data are suitably close to the rarefaction wave at the initial time, the solution is proven to tend toward the rarefaction wave as time goes to infinity. The proof is given by an elementaryL2 energy method.

Control of ion‐velocity distributions in laser–target interaction experiments

Abstract: The width of ion‐velocity distributions from laser‐produced plasmas can be controlled experimentally by varying the size of the laser spot. This ion‐velocity width is determined primarily by whether the ions are mostly in the rarefaction or steady‐state regime. It is not dominated by the thermal distribution of the ions, as is sometimes assumed. A simple analytic theory shows that the distribution width is governed by the scaling parameter rs/cτ, where rs is the focal spot radius, c is the sound speed, and τ is the laser pulse length.

Orion Aerodynamics for Hypersonic Free Molecular to Continuum Conditions

Abstract: Numerical simulations are performed for the Orion Crew Module, previously known as the Crew Exploration Vehicle (CEV) Command Module, to characterize its aerodynamics during the high altitude portion of its reentry into the Earth's atmosphere, that is, from free molecular to continuum hypersonic conditions. The focus is on flow conditions similar to those that the Orion Crew Module would experience during a return from the International Space Station. The bulk of the calculations are performed with two direct simulation Monte Carlo (DSMC) codes, and these data are anchored with results from both free molecular and Navier-Stokes calculations. Results for aerodynamic forces and moments are presented that demonstrate their sensitivity to rarefaction, that is, for free molecular to continuum conditions (Knudsen numbers of 111 to 0.0003). Also included are aerodynamic data as a function of angle of attack for different levels of rarefaction and results that demonstrate the aerodynamic sensitivity of the Orion CM to a range of reentry velocities (7.6 to 15 km/s).

Dissipative shock waves generated by a quantum-mechanical piston.

Abstract: The piston shock problem is a prototypical example of strongly nonlinear fluid flow that enables the experimental exploration of fluid dynamics in extreme regimes. Here we investigate this problem for a nominally dissipationless, superfluid Bose-Einstein condensate and observe rich dynamics including the formation of a plateau region, a non-expanding shock front, and rarefaction waves. Many aspects of the observed dynamics follow predictions of classical dissipative—rather than superfluid dispersive—shock theory. The emergence of dissipative-like dynamics is attributed to the decay of large amplitude excitations at the shock front into turbulent vortex excitations, which allow us to invoke an eddy viscosity hypothesis. Our experimental observations are accompanied by numerical simulations of the mean-field, Gross-Pitaevskii equation that exhibit quantitative agreement with no fitting parameters. This work provides an avenue for the investigation of quantum shock waves and turbulence in channel geometries, which are currently the focus of intense research efforts. There is increasing interest in understanding the non-equilibrium phenomena in quantum fluids. Here, the authors show dissipative, viscous shock and rarefaction wave dynamics emerging from the turbulent, superfluid flow of an elongated BEC of ultracold Rb atoms driven by a quantum-mechanical piston.