Shock wave

About: Shock wave is a research topic. Over the lifetime, 36184 publications have been published within this topic receiving 635848 citations. The topic is also known as: Shock waves & shockwave.

Physical Model of the Swept Shock Wave/Boundary-Layer Interaction Flowfield

Abstract: New data are presented on the structure of fin-induced, swept shock/boundary-layer interactions. These data are obtained using a nonintrusive planar laser scattering (PLS) imaging technique. A range of interaction strengths, from barely separated to very strongly separated, is covered for freestream Mach numbers of 3 and 4. These new data, when combined with previous results on the flowfield and interaction "footprint," are sufficient to allow the construction of a physical model for the swept interaction flowfield structure and behavior. This physical model is presented and discussed in terms of six detailed flowfield maps which take advantage of the inherent quasiconical behavior of the class of interactions considered.

Resolution of a shock in hyperbolic systems modified by weak dispersion.

Abstract: We present a way to deal with dispersion-dominated “shock-type” transition in the absence of completely integrable structure for the systems that one may characterize as strictly hyperbolic regularized by a small amount of dispersion. The analysis is performed by assuming that the dispersive shock transition between two different constant states can be modeled by an expansion fan solution of the associated modulation (Whitham) system for the short-wavelength nonlinear oscillations in the transition region (the so-called Gurevich-Pitaevskii problem). We consider both single-wave and bidirectional systems. The main mathematical assumption is that of hyperbolicity of the Whitham system for the solutions of our interest. By using general properties of the Whitham averaging for a certain class of nonlinear dispersive systems and specific features of the Cauchy data prescription on characteristics we derive a set of transition conditions for the dispersive shock, actually bypassing full integration of the modulation equations. Along with the Korteweg-de Vries (KdV) and modified KdV (mKdV) equations as model examples, we consider a nonintegrable system describing fully nonlinear ion-acoustic waves in collisionless plasma. In all cases our transition conditions are in complete agreement with previous analytical and numerical results.

Surface reactions of metal clusters I: The fast flow cluster reactor

Abstract: A new fast flow device for the study of metal cluster reactions in the gas phase is described and characterized. The new device utilizes metal clusters made by laser vaporization of an appropriate metal target mounted in the throat of a supersonic nozzle which exhausts into a fast‐flow reaction tube. Reactants are injected into the flowing helium–metal cluster mixture at a point in the flow tube where shock waves have reheated the gas to roughly 320 K. Turbulence in the wake of these shock waves produces efficient mixing of the reactants. Measurement of the flow properties of this reaction tube indicate a residence time of 150–200 μs with an average density of helium buffer gas equivalent to 50–100 Torr at room temperature. Subsequent free expansion of this reaction mixture into a large vacuum chamber produces a supersonic beam with extensive cooling of the various constituents in the mixture (pyrazine was measured to be rotationally cooled to 10 K). The new cluster reaction device is, therefore, an excellent source for future studies of the jet‐cooled metal cluster reaction products themselves.

Nonstationarity of strong collisionless quasiperpendicular shocks: Theory and full particle numerical simulations

Abstract: Whistler waves are an intrinsic feature of the oblique quasiperpendicular collisionless shock waves. For supercritical shock waves, the ramp region, where an abrupt increase of the magnetic field occurs, can be treated as a nonlinear whistler wave of large amplitude. In addition, oblique shock waves can possess a linear whistler precursor. There exist two critical Mach numbers related to the whistler components of the shock wave, the first is known as a whistler critical Mach number and the second can be referred to as a nonlinear whistler critical Mach number. When the whistler critical Much number is exceeded, a stationary linear wave train cannot stand ahead of the ramp. Above the nonlinear whistler critical Mach number, the stationary nonlinear wave train cannot exist anymore within the shock front. This happens when the nonlinear wave steepening cannot be balanced by the effects of the dispersion and dissipation. In this case nonlinear wave train becomes unstable with respect to overturning. In the present paper it is shown that the nonlinear whistler critical Mach number corresponds to the transition between stationary and nonstationary dynamical behavior of the shock wave. The results of the computer simulations making use of the 1D full particle electromagnetic code demonstrate that the transition to the nonstationarity of the shock front structure is always accompanied by the disappearance of the whistler wave train within the shock front. Using the two-fluid MHD equations, the structure of nonlinear whistler waves in plasmas with finite beta is investigated and the nonlinear whistler critical Mach number is determined. It is suggested a new more general proof of the criteria for small amplitude linear precursor or wake wave trains to exist.