Oblique shock

About: Oblique shock is a research topic. Over the lifetime, 6551 publications have been published within this topic receiving 119823 citations.

Potential theory for regular and mach reflection of a shock at a wedge

Abstract: If a plane shock hits a wedge, a self-similar pattern of reflected shocks travels outward as the shock moves forward in time. The nature of the pattern is explored for weak incident shocks (strength b) and small wedge angles 2θw through potential theory, a number of different scalings, some study of mixed equations and matching asymptotics for the different scalings. The self-similar equations are of mixed type. A linearization gives a linear mixed flow valid away from a sonic curve. Near the sonic curve a shock solution is constructed in another scaling except near the zone of interaction between the incident shock and the wall where a special scaling is used. The parameter β = c1θ2w(γ + 1)b ranges from 0 to ∞. Here γ is the polytropic constant and C1 is the sound speed behind the incident shock. For β > 2 regular reflection (weak or strong) can occur and the whole pattern is reconstructed to lowest order in shock strength. For β < 1/2 Mach reflection occurs and the flow behind the reflection is subsonic and can be constructed in principle (with an open elliptic problem) and matched. The case β = 0 can be solved. For 1/2 < β < 2 or even larger β the flow behind a Mach reflection may be transonic and further investigation must be made to determine what happens. The basic pattern of reflection is an almost semi-circular shock issuing, for regular reflection, from the reflection point on the wedge and for Mach reflection, matched with a local interaction flow. Assuming their nature, choosing the least entropy generation, the weak regular reflection will occur for β sufficiently large (von Neumann paradox). An accumulation point of vorticity occurs on the wedge above the leading point. © 1994 John Wiley & Sons, Inc.

The structure of magneto-hydrodynamic shock waves

Abstract: The equations describing the detailed structure of magneto-hydrodynamic shocks are derived and their solutions discussed in the special cases of high or low electrical conductivity. For high conductivity the shock front has a width of several mean free paths. For low conductivity, if the initial magnetic field is smaller than a certain critical value, a sharp shock is preceded by a wide region in which the field, velocity and temperature change slowly; if the field is larger than this critical value, then no sharp shock occurs and all the variables change slowly over a wide region. A small double layer of charge is built up on the shock front as a result of the Hall effect.

Fast-shock formation in line-tied magnetic reconnection models of solar flares

Abstract: In a previous study by the author, an approximately stationary fast shock was tentatively identified in a numerical experiment designed to study line-tied magnetic reconnection. Here the evidence for the occurrence of a stationary fast shock is reexamined, and the previous identification is confirmed. In the numerical experiment, line-tied reconnection is modeled by a configuration which produces two supermagnetosonic outflow jets - one directed upward, away from the photosphere, and one directed downward, toward an arcade of closed magnetic loops tied to the photosphere. The fast shock occurs when the downward-directed jet encounters the obstacle formed by the closed loops. Although the existence of a stationary, or nearly stationary, fast shock is confirmed, the transition from the supermagnetosonic flow region upstream of the shock to the nearly static region downstream of the shock is more complicated than was previously thought. Immediately downstream of the shock, there exists a deflection sheath in which the submagnetosonic flow coming out of the shock is diverted around the region of static closed loops. The MHD jump conditions are used to investigate the characteristics of the fast shock and to show that a stationary shock cannot exist unless accompanied by a deflection sheath. Analysis of the shock's location and dimensions suggests that such fast shocks may contribute to particle acceleration and to thermal condensation in flares.

Reynolds-Averaged Navier-Stokes Study of the Shock-Buffet Instability Mechanism

Abstract: A study of shock-buffet onset and instability mechanism via Reynolds-averaged Navier―Stokes simulations on several airfoils is presented. The numerical setup and the Spalart―AUmaras turbulence closure are validated based on wind-tunnel data from NACA 0012 and RA16SC1 airfoils. The paper presents simulations of the flow past three • airfoils: the subsonic NACA 0012, the supercritical RA16SC1, and the thin, transonic/supersonic NACA 64A204, at pre- and postbuffet conditions, and within a cycle of developed shock buffet. The shock-buffet cycle is found to be »■• similar in nature for all airfoils, originating in unstable interaction of the shock and the separation bubble. Simulation results support the notion that buffet onset is not related to the bursting of the separation bubble behind the shock. Shock-buffet categorizing is posited as a transonic prestall instability phenomenon that depends on the shock strength and location. Shock-buffet onset conditions occur when the shock position is behind and sufficiently close to the upper-surface maximum curvature location. Additionally, it is suggested that offset conditions are when the shock is at an upstream location and the flow aft of it is fully separated.