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.

Magnetohydrodynamic Shock Waves in Molecular Clouds

Abstract: The fluid dynamics of MHD shock waves in magnetized molecular gas is reviewed. The different types of shock solutions, and the circumstances under which the different types occur, are delineated. Current theoretical work on C*- and J-type shocks, and on the stability of C-type shocks, is briefly described. Observations of the line emission from MHD shocks in different regions appear to be in conflict with theoretical expectations for single, plane-parallel shocks. Replacement of plane-parallel shocks by bow shocks may help reconcile theory and observation, but it is also possible that the observed shocks may not be “steady”, or that theoretical models have omitted some important physics

Radio emission from the unusual supernova 1998bw and its association with the γ-ray burst of 25 April 1998

Abstract: Data accumulated over the past year strongly favour the idea that γ-ray bursts lie at cosmological distances, although the nature of the power source remains unclear. Here we report radio observations of the supernova SN1998bw, which exploded at about the same time, and in about the same direction, as the γ-ray burst GRB980425. At its peak, the supernova was unusually luminous at radio wavelengths. A simple interpretation of the data requires that the source expanded with an apparent velocity of at least twice the speed of light, indicating that the supernova was accompanied by a shock wave moving at relativistic speeds (the ejects of supernovae are typically characterized by non-relativistic velocities). The energy of the shock is at least 10^(49)erg, with an inferred ejecta mass of 10^(-5) solar masses, and we suggest that the early phase of this shock wave produced the burst of γ-rays. Although in general the properties of supernovae are very different from those of γ-ray bursts, we argue that this unusual supernova establishes a second class of γ-ray burst, which is distinctly different from the cosmological kind.

Shock wave emission and cavitation bubble generation by picosecond and nanosecond optical breakdown in water

Abstract: Shock wave emission and cavitation bubble expansion after optical breakdown in water with Nd:YAG laser pulses of 30‐ps and 6‐ns duration is investigated for energies between 50 μJ and 10 mJ which are often used for intraocular laser surgery. Time‐resolved photography is applied to measure the position of the shock front and the bubble wall as a function of time. The photographs are used to determine the shock front and bubble wall velocity as well as the shock wave pressure as a function of time or position. Calculations of the bubble formation and shock wave emission are performed using the Gilmore model of cavitation bubble dynamics and the Kirkwood–Bethe hypothesis. The calculations are based on the laser pulse duration, the size of the plasma, and the maximally expanded cavitation bubble, i.e., on easily measurable parameters. They yield the dynamics of the bubble wall, the pressure evolution inside the bubble, and pressure profiles in the surrounding liquid at fixed times after the start of the laser...

Interaction of weak shock waves with cylindrical and spherical gas inhomogeneities

Abstract: The interaction of a plane weak shock wave with a single discrete gaseous inhomogeneity is studied as a model of the mechanisms by which finite-amplitude waves in random media generate turbulence and intensify mixing. The experiments are treated as an example of the shock-induced Rayleigh-Taylor instability. or Richtmyer-Meshkov instability, with large initial distortions of the gas interfaces. The inhomogeneities are made by filling large soap bubbles and cylindrical refraction cells (5 cm diameter) whose walls are thin plastic membranes with gases both lighter and heavier than the ambient air in a square (8.9 cm side shock-tube text section. The wavefront geometry and the deformation of the gas volume are visualized by shadowgraph photography. Wave configurations predicted by geometrical acoustics, including the effects of refraction, reflection and diffraction, are compared to the observations. Departures from the predictions of acoustic theory are discussed in terms of gasdynamic nonlinearity. The pressure field on the axis of symmetry downstream of the inhomogeneity is measured by piezoelectric pressure transducers. In the case of a cylindrical or spherical volume filled with heavy low-sound-speed gas the wave which passes through the interior focuses just behind the cylinder. On the other hand, the wave which passes through the light high-sound-speed volume strongly diverges. Visualization of the wavefronts reflected from and diffracted around the inhomogeneities exhibit many features known in optical and acoustic scattering. Rayleigh-Taylor instability induced by shock acceleration deforms the initially circular cross-section of the volume. In the case of the high-sound-speed sphere, a strong vortex ring forms and separates from the main volume of gas. Measurements of the wave and gas-interface velocities are compared to values calculated for one-dimensional interactions and for a simple model of shock-induced Rayleigh-Taylor instability. The circulation and Reynolds number of the vortical structures are calculated from the measured velocities by modeling a piston vortex generator. The results of the flow visualization are also compared with contemporary numerical simulations.