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, a methodology is developed to measure solar-wind compression and rarefaction using the orientations of solar wind current sheets, based on the current-sheet orientations, on magnetic field strength, on the intensity of the electron strahl, and on the negative vorticity, an inflection point is taken as the best indicator of the trailing-edge stream interface.
Abstract: The trailing-edge rarefactions of 54 high-speed streams at 1AU are analyzed. The temporal durations of the trailing-edge rarefactions agree with ballistic calculations based on the observed speeds of the fast and slow wind bounding the rarefactions. A methodology is developed to measure solar-wind compression and rarefaction using the orientations of solar-wind current sheets. One focus is to determine the signature that best describes the location of the trailing-edge stream interface between coronal-hole-origin plasma and streamer-belt-origin plasma; based on the current-sheet orientations, on the magnetic-field strength, on the intensity of the electron strahl, and on the intensity of the negative vorticity, an inflection point in the temporal profile of the solar-wind velocity is taken as the best indicator of the trailing-edge stream interface. Computer simulations support this choice. Using superposed-epoch analysis, the plasma properties and turbulence properties of trailing-edge rarefactions are surveyed. Whereas the signatures of the coronalhole/streamer-belt (slow-wind/fast-wind) boundary in the leading edge (corotating interaction region) stream interface are simultaneous, they are not simultaneous in the trailing edge, with ion-charge-state signatures occurring on average 13.7h prior to the proton entropy signature. It is suggested that differences in the leading and trailing edges of coronal holes on the Sunmight account for the differences in the leading and trailing edges of high-speed streams at 1AU: the formation timescales, heating timescales, and charge-state-equilibration timescales of closed flux loops in the corona might be involved.
32 citations
TL;DR: In this article, the authors discussed the shock structure in macroscopic multi-temperature model of gaseous mixtures, recently established within the framework of extended thermodynamics.
Abstract: The paper discusses the shock structure in macroscopic multi-temperature model of gaseous mixtures, recently established within the framework of extended thermodynamics. The study is restricted to weak and moderate shocks in a binary mixture of ideal gases with negligible viscosity and heat conductivity. The model predicts the existence of temperature overshoot of heavier constituent, like more sophisticated approaches, but also puts in evidence its non-monotonic behavior not documented in other studies. This phenomenon is explained as a consequence of weak energy exchange between the constituents, either due to large mass difference, or large rarefaction of the mixture. In the range of small Mach number it is also shown that shock thickness (or equivalently, the inverse of Knudsen number) decreases with the increase of Mach number, as well as when the mixture tends to behave like a single-component gas (small mass difference and/or presence of one constituent in traces).
32 citations
TL;DR: In this article, a model for the liquid/vapor phase transitions in a shock tube is discussed, and the existence of traveling waves under two different scalings is studied, for the first scaling, where the diffusion of different phases is very small relative to typical reaction time for the growth of phases while the viscosity is comparable to the reaction time.
32 citations
TL;DR: In this paper, the authors explore the behavior of the Rayleigh-Taylor instability initiated with a diffuse interface and perform experiments in which an interface between two gases of differing density is made unstable by acceleration generated by a rarefaction wave.
Abstract: Theory and experiments are reported that explore the behaviour of the Rayleigh–Taylor instability initiated with a diffuse interface. Experiments are performed in which an interface between two gases of differing density is made unstable by acceleration generated by a rarefaction wave. Well-controlled, diffuse, two-dimensional and three-dimensional, single-mode perturbations are generated by oscillating the gases either side to side, or vertically for the three-dimensional perturbations. The puncturing of a diaphragm separating a vacuum tank beneath the test section generates a rarefaction wave that travels upwards and accelerates the interface downwards. This rarefaction wave generates a large, but non-constant, acceleration of the order of , where is the acceleration due to gravity. Initial interface thicknesses are measured using a Rayleigh scattering diagnostic and the instability is visualized using planar laser-induced Mie scattering. Growth rates agree well with theoretical values, and with the inviscid, dynamic diffusion model of Duff et al. (Phys. Fluids, vol. 5, 1962, pp. 417–425) when diffusion thickness is accounted for, and the acceleration is weighted using inviscid Rayleigh–Taylor theory. The linear stability formulation of Chandrasekhar (Proc. Camb. Phil. Soc., vol. 51, 1955, pp. 162–178) is solved numerically with an error function diffusion profile using the Riccati method. This technique exhibits good agreement with the dynamic diffusion model of Duff et al. for small wavenumbers, but produces larger growth rates for large-wavenumber perturbations. Asymptotic analysis shows a decay in growth rates as for large-wavenumber perturbations.
32 citations
TL;DR: The present study is the first to demonstrate consonant coproduction in terms of oral pressure, and to report on coarticulatory effects involving four sequenced segments.
Abstract: Aerodynamic evidence indicates the existence of overlapped labial//velar sequences in Korean. Oral pressure readings for [ipku] show a brief rarefaction in oral pressure during the consonantal sequenc
31 citations