Shock tube

About: Shock tube is a research topic. Over the lifetime, 6963 publications have been published within this topic receiving 99372 citations.

Smoothed particle hydrodynamics simulations of ultrarelativistic shocks with artificial viscosity

Abstract: We present a fully Lagrangian conservation form of the general relativistic hydrodynamic equations for perfect fluids with artificial viscosity in a given arbitrary background spacetime. This conservation formulation is achieved by choosing suitable Lagrangian time evolution variables, from which the generic fluid variables of rest-mass density, 3-velocity, and thermodynamic pressure have to be determined. We present the corresponding equations for an ideal gas and show the existence and uniqueness of the solution. On the basis of the Lagrangian formulation we have developed a three-dimensional general relativistic smoothed particle hydrodynamics (SPH) code using the standard SPH formalism as known from nonrelativistic fluid dynamics. One-dimensional simulations of a shock tube and a wall shock are presented together with a two-dimensional test calculation of an inclined shock tube. With our method we can model ultrarelativistic fluid flows including shocks with Lorentz factors of even 1000.

Some Unexpected Results of Shock‐Heating Xenon

Abstract: Results from a detailed experimental study of the structure of pressure‐driven incident shock waves in very pure xenon contained in a thoroughly pumped Pyrex shock tube are presented and discussed. As a result of some optical studies of the luminous structure of the shocks, the following features of the luminosity delay time were discovered: independence of the pressure in the undisturbed xenon in the range 0.75 to 4.0 mm Hg, dependence on shock velocity in a way not explainable on the basis of reasonable volume processes alone, and dependence on shock tube diameter. The visible luminosity from the shock was found to terminate well in advance of the measured position of the xenon‐driver interface. This is indicative of severe radiation cooling. The visible luminosity was also found to be profoundly altered by the addition of impurities either in the xenon itself or in the driver. The spectrum of the delayed luminosity in the region from 3000 to 10 000 A was studied with an electronic‐recording time‐resolving spectrometer and found to consist of xenon atom lines superimposed on a strong continuum. The continuum may reasonably be attributed to dissociative transitions from bound excited states of the Xe2 molecule related to the xenon atom levels 7 pKJ and above to unbound Xe2 states related to the atomic levels 6s11 and 6s12. Positive electrical signals, observed during the passage of the shock through external metal rings, are attributed to ejection of electrons from the shock tube walls by photoelectric action and/or metastable atoms. In addition, two different types of electrical precursors were observed. The first was observed under the usual conditions, namely that the shock was sufficiently strong to cause the delayed luminosity. The second was observed in some experiments in which the shock was too weak to cause the delayed luminosity. Both could be due to a photoelectric effect on the shock tube walls, but the precursor observed in the absence of the delayed luminosity may be also due to diffusion of electrons ahead of the shock front. The present experiments strongly indicate that shock tube experiments of others may need reinterpretation.

Methane Ignition in a Shock Tube with High Levels of CO2 Dilution: Consideration of the Reflected-Shock Bifurcation

Abstract: Experiments were performed in a shock-tube facility to examine experimentally the kinetic effect, if any, of excess amounts of CO2 as part of natural-gas-based fuel–oxidizer mixtures. An important aspect of these experiments was to also observe the role excess amounts of CO2 play in causing nonidealities, particularly shock bifurcation, in shock-tube experiments using real (nondilute) fuel–air mixtures. Mixtures were composed of methane fuel at an equivalence ratio of 0.5 to represent a typical natural gas in a modified “air” mixture designed to study the effect of large levels of CO2 dilution. These oxidizer compositions maintained constant levels of O2 while exchanging N2 for CO2 in stages to give oxidizer mixture concentrations ranging from (0.21O2 + 0.79N2) to (0.21O2 + 0.79CO2). Low-pressure and high-pressure (near 1 and 10 atm, respectively) experiments were conducted over an approximate temperature range of 1450 to 1900 K. Results showed that the observed effect of CO2 relating to reflected-shock b...

Richtmyer-Meshkov instability induced by the interaction of a shock wave with a rectangular block of SF6

Abstract: In this article the interaction of a shock wave with a rectangular block of sulphur hexafluoride (SF6), occupying part of the test section of a shock tube, is studied by experimental and numerical means. The difference between the ratios of the specific heats of the two gases (air and SF6) gives rise to numerical problems (generation of spurious waves at their interface). This necessitated the development of a multifluid algorithm (augmented Navier-Stokes formulation). The governing equations are based on a thermodynamically consistent and fully conservative formulation. A Riemann-problem-based scheme (the weighted average flux method) is used to integrate the hyperbolic part of the system. To this end, a new approximate Riemann problem solver has been formulated to account for the variable ratio of specific heats. The resulting algorithm was implemented in an adaptive mesh refinement code, which allowed high-resolution simulations to be performed on desktop computers. The evolution of the flow is well ca...