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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, a method based on Riemann interactions is proposed for the analysis of two different nozzle geometries and supersonic flow, which is ideal for conceptual design, control design, or control evaluation studies.
Abstract: interaction between operating condition and plume shape complicates the analysis of such nozzles compared to traditional bell nozzles. A method that is based on Riemann interactions is proposed for the analysis of two such nozzle geometries. The method assumes two-dimensional geometries and supersonic flow. Unlike the method of characteristics, this method accounts explicitly for the presence of oblique shocks and curved shear layers. Comparisons to both experiment and computational fluid dynamics are shown. The solution method requires no grid generation and typically runs in less than a minute on a single desktop computer, which is ideal for conceptual design, control design, or control evaluation studies. It includes high-temperature gas modeling and finite-rate chemistry. Nomenclature A = area c = specific heat Ex = momentum conservation error H = height or length scale M = Mach number nexp = number of discrete waves in expansion nsp = number of species p = pressure r = length of characteristic R = normalized gas constant T = temperature u = magnitude of flow velocity W = molecular weight x, y = spatial coordinates Y = mass fraction = angle between wave and upstream flow = ratio of specific heats = deflection angle across a wave = angle of deflection caused by boundary layer = flowpath angle = momentum thickness " = ratio of static pressures = Mach angle = Prandtl-Meyer angle = streamwise coordinate = density = angle between wave and x-axis ˙ ! = molar rate of production

40 citations

Journal ArticleDOI
TL;DR: The V-shock model has been identified as the primary mechanism for the acceleration of electrons responsible for the discrete aurora as mentioned in this paper, and it is also shown to be a generalization of the one-dimensional double layer model, which is an ion acoustic soliton Doppler shifted to zero frequency.
Abstract: The V-shock is identified as the primary mechanism for the acceleration of electrons responsible for the discrete aurora A brief review of the evidence supporting the V-shock model is given, including the dynamics of auroral striations, anomalous motion of barium plasma at high altitudes and in-situ observations of large electric fields The V-shock is a nonlinear, n = 0 ion cyclotron mode soliton, Doppler shifted to zero frequency The V-shock is also shown to be a generalization of the one-dimensional double layer model, which is an ion acoustic soliton Doppler shifted to zero frequency The essential difference between the double layer theory and the theory for the oblique, current-driven, laminar electrostatic shock is that the plasma dielectric constant in directions perpendicular to the magnetic field is c 2/V /2 , where V a is the Alfven velocity; but the plasma dielectric constant parallel to the magnetic field is unity Otherwise, in the limit that the shock thickness perpendicular to the magnetic field is much larger than an ion gyroradius, the equations describing the double layer and the oblique shock are the same The V-shock, while accounting for the acceleration of auroral electrons, requires an energy source and mechanism for generating large potential differences perpendicular to the magnetic field An energy source is the earthward streaming protons coming from the distant magnetospheric tail It is shown how these protons can be energized by the cross-tail electric field, which is the tailward extension of the polar cap dawn-to-dusk electric field The local, large cross-field potential differences associated with the V-shock are seen to be the result of a non-linear, E × B drift turbulent cascade which transfers energy from small- to large-scale sizes Energy at the smallest scale sizes comes from the kinetic energy in the ion cyclotron motion of the earthward streaming protons, which are unstable against the zero-frequency flute-mode instability The review points out the gaps in our understanding of the mechanism of the diffuse aurora and the mechanism of the auroral substorm

40 citations

Journal ArticleDOI
TL;DR: In this article, the shape of the solar-flare-produced strong shock fronts in the solar wind has been calculated, large-scale variations in the ambient medium being taken into account.
Abstract: The shapes expected for solar-flare-produced strong shock fronts in the solar wind have been calculated, large-scale variations in the ambient medium being taken into account. It has been shown that for reasonable ambient solar wind conditions the mean and the standard deviation of the east-west shock normal angle are in agreement with experimental observations including shocks of all strengths. The results further suggest that near a high-speed stream it is difficult to distinguish between corotating shocks and flare-associated shocks on the basis of the shock normal alone. Although the calculated shapes are outside the range of validity of the linear approximation, these results indicate that the variations in the ambient solar wind may account for large deviations of shock normals from the radial direction.

40 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202369
2022142
2021106
202090
201992
2018102