Rarefaction

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

Analysis of Rarefaction Effects in the Hypersonic Rarefied Wind Tunnel

Abstract: A hypersonic rarefied wind tunnel (HRWT) has lately been developed at Japan Aerospace Exploration Agency. Flow characteristics of hypersonic rarefied flows have been investigated experimentally and numerically in this work. By conducting experiments of a pendulous sphere model and pitot tubes, we have probed flow characteristics in the test section. We have improved the understandings of the hypersonic rarefied flows by integrating a numerical approach with the HRWT measurement. Moreover, rarefaction effects on the impact pressure measurement have been analyzed by carrying out particle simulations, and good agreement was obtained between the measured and computed impact pressure. Finally, a method for the determination of surface accommodation parameters in HRWT has been proposed by utilizing a three degree-of-freedom measurement system with a plate model.

Nonlinear stability of centered rarefaction waves of the Jin-Xin relaxation model for conservation laws.

Abstract: We study the asymptotic equivalence of the Jin-Xin relaxation model and its formal limit for genuinely nonlinear 2 2 conservation laws. The initial data is allowed to have jump discontinuities corresponding to centered rarefaction waves, which includes Riemann data connected by rarefaction curves. We show that, as long as the initial data is a small perturbation of a constant state, the solution for the relaxation system exists globally in time and converges, in the zero relaxation limit, to the solution of the corresponding conservation law uniformly except for an initial layer.

The Effect of the Pre-Detonation Stellar Internal Velocity Profile on the Nucleosynthetic Yields in Type Ia Supernova

Abstract: A common model of the explosion mechanism of Type Ia supernovae is based on a delayed detonation of a white dwarf. A variety of models differ primarily in the method by which the deflagration leads to a detonation. A common feature of the models, however, is that all of them involve the propagation of the detonation through a white dwarf that is either expanding or contracting, where the stellar internal velocity profile depends on both time and space. In this work, we investigate the effects of the pre-detonation stellar internal velocity profile and the post-detonation velocity of expansion on the production of alpha-particle nuclei, including Ni56, which are the primary nuclei produced by the detonation wave. We perform one-dimensional hydrodynamic simulations of the explosion phase of the white dwarf for center and off-center detonations with five different stellar velocity profiles at the onset of the detonation. We observe two distinct post-detonation expansion phases: rarefaction and bulk expansion. Almost all the burning to Ni56 occurs only in the rarefaction phase, and its expansion time scale is influenced by pre-existing flow structure in the star, in particular by the pre-detonation stellar velocity profile. We find that the mass fractions of the alpha-particle nuclei, including Ni56, are tight functions of the empirical physical parameter rho_up/v_down, where rho_up is the mass density immediately upstream of the detonation wave front and v_down is the velocity of the flow immediately downstream of the detonation wave front. We also find that v_down depends on the pre-detonation flow velocity. We conclude that the properties of the pre-existing flow, in particular the internal stellar velocity profile, influence the final isotopic composition of burned matter produced by the detonation.

Modeling of Shock-Wave Loading of Liquid Volumes

Abstract: Cavitation evolution dynamics in cylindrical liquid volumes under the axial loading by an exploding wire is studied experimentally and theoretically. The method of dynamic head registration is used to study the structure of two phase flows formed and evaluate characteristic time of cavitation liquid fracture. As a result of numerical simulation of the experiments, which was performed in a single-velocity two-phase model approximation, the energy transformation mechanism is determined at shock interaction with a free real liquid surface. A two-phase model is suggested to describe the irreversible development of a cavitation zone formed as a result of the mentioned interaction. The model is based on practically instantaneous tensile-stress relaxation in a centered rarefaction wave and further inertial evolution of the process.