Topic
Oblique shock
About: Oblique shock is a research topic. Over the lifetime, 6551 publications have been published within this topic receiving 119823 citations.
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TL;DR: In this paper, the frequency response of a normal shock in a diverging channel is calculated for application to problems of pressure oscillations in ramjet engines, and two limits of a linearized analysis arc are discussed: one represents isentropic flow on both sides of a shock wave; the other may be a crude estimate to the influence of flow separation induced by the wave.
Abstract: The frequency response of a normal shock in a diverging channel is calculated for application to problems of
pressure oscillations in ramjet engines. Two limits of a linearized analysis arc discussed: one represents isentropic
flow on both sides of a shock wave; the other may be a crude appr'l'I;imation to the influence of flow separation
induced hy the wave. Numerical results arc given, and the influences of the shock wave on oscillations in the
engine are discus,ed.
130 citations
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TL;DR: In this paper, the Richtmyer-Meshkov instability was removed by the use of a novel technique in which the interface is formed by flowing light (N2) and heavy (SF6) gases from opposite ends of a vertical shock tube.
Abstract: Previous Richtmyer–Meshkov instability experiments carried out in shock tubes have been hampered by the need to separate the two gases with a thin plastic membrane. As a result, many of these experiments have had poor agreement with the linear stability theory of Richtmyer [Commun. Pure Appl. Math. 23, 297 (1960)]. This limitation has been removed in the present investigation by the use of a novel technique in which the interface is formed by flowing light (N2) and heavy (SF6) gases from opposite ends of a vertical shock tube. Both gases exit the shock tube through slots in the test section walls leaving behind a flat motionless interface which is then given a sinusoidal initial shape by gently oscillating the shock tube at a prescribed frequency in the horizontal direction. A weak shock wave (Ms=1.10), generated in the shock tube, impacts the interface and produces the instability. Photographs of the interface, which is visualized by seeding the heavy gas with a water droplet fog and illuminating it with...
129 citations
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TL;DR: In this article, three traveling disturbances recorded in the absorption line of Helium I at 10830 A (HeI), analogous to HαMoreton waves, are analyzed and the morphology and kinematics of the wavefronts are described in detail.
Abstract: Three traveling disturbances recorded in the absorption line of Helium I at 10830 A (HeI), analogous to HαMoreton waves, are analyzed. The morphology and kinematics of the wavefronts are described in detail. The HeI wave appears as an expanding arc of increased absorption roughly corresponding to the Hα disturbance, although not as sharply defined. HeI perturbations consist of a relatively uniform diffuse component and a patchy one that appears as enhanced absorption in HeI mottles. It leads the Hα front by some 20 Mm and can be followed to considerably larger distances than in Hα observations. Behind the front stationary areas of reduced HeI absorption develop, resembling EUV coronal dimming. The observed HeI as well as the Hα disturbances show a deceleration of the order of 100-1000 ms −2 . Moreover, in the event where Hα ,H eI, and EUV wavefronts are observed, all of them follow closely related kinematical curves, indicating that they are a consequence of a common disturbance. The analysis of spatial perturbation profiles indicates that HeI disturbances consist of a forerunner and a main dip,the latterbeing cospatial withthe Hαdisturbance. The properties and behavior of the wavefronts can be comprehended as a consequence of a fast-mode MHD coronal shock whose front is weakly inclined to the solar surface. The Hα disturbance and the main HeI dip are a consequence of the pressure jump in the corona behind the shock front. The HeI forerunner might be caused by thermal conduction from the oblique shock segments ahead of the shock-chromosphere intersection, or by electron beams accelerated in the quasi-perpendicular section of the shock.
128 citations
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TL;DR: In this article, a Monte Carlo technique was developed for self-consistently calculating the hydrodynamic structure of oblique, steady state shocks, together with the first-order Fermi acceleration process and associated nonthermal particle distributions.
Abstract: The solution of the nonlinear diffusive shock acceleration problem, where the pressure of the non-thermal population is sufficient to modify the shock hydrodynamics, is widely recognized as a key to understanding particle acceleration in a variety of astrophysical environments. We have developed a Monte Carlo technique for self-consistently calculating the hydrodynamic structure of oblique, steady state shocks, together with the first-order Fermi acceleration process and associated nonthermal particle distributions. This is the first internally consistent treatment of modified shocks that includes cross-field diffusion of particles. Our method overcomes the injection problem faced by analytic descriptions of shock acceleration and the lack of adequate dynamic range and artificial suppression of cross-field diffusion faced by plasma simulations; it currently provides the most broad and versatile description of collisionless shocks undergoing efficient particle acceleration. We present solutions for plasma quantities and particle distributions upstream and downstream of shocks, illustrating the strong differences observed between nonlinear and test particle cases. It is found that, for strong scattering, there are only marginal differences in the injection efficiency and resultant spectra for two extreme scattering modes, namely large-angle scattering and pitch-angle diffusion, for a wide range of shock parameters, i.e., for nonper-pendicular subluminal shocks with field obliquities less than or equal to 75° and de Hoffmann-Teller frame speeds much less than the speed of light.
127 citations
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TL;DR: In this paper, a numerical scheme is developed which automatically locates the angle at which a shock might be expected to cross the computing grid then constructs separate finite difference formulas for the flux components normal and tangential to this direction.
127 citations