Oblique shock

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

The structural response of cylindrical shells to internal shock loading

Abstract: The internal shock loading of cylindrical shells can be represented as a step load advancing at constant speed. Several analytical models are available to calculate the structural response of shells to this type of loading. These models show that the speed of the shock wave is an important parameter. In fact, for a linear model of a shell of infinite length, the amplitude of the radial deflection becomes unbounded when the speed of the shock wave is equal to a critical velocity. It is evident that simple (static) design formulas are no longer accurate in this case. The present paper deals with a numerical and experimental study on the structural response of a thin aluminum cylindrical shell to shock loading. Transient finite element calculations were carried out for a range of shock speeds. The results were compared to experimental results obtained with the GALCIT 6-in. shock tube facility. Both the experimental and the numerical results show an increase in amplitude near the critical velocity, as predicted by simple steady-state models for shells of infinite length. However, the finite length of the shell results in some transient phenomena. These phenomena are related to the reflection of structural waves and the development of the deflection profile when the shock wave enters the shell.

An experimental investigation of the initial stages of the dispersion of dust by shock waves

Abstract: The first few hundred microseconds after the passage of a shock wave in air over dust deposited on a horizontal surface in a shock tube have been studied photographically. The effects of shock wave Mach number, the type of dust and the depth of the deposit were investigated. It was discovered that there is a small delay between the passage of the shock wave and the raising of dust at a point. This delay was found to depend upon the depth of the deposit. The profile of the dust cloud formed was measured with one type of dust over a range of shock wave speeds and found to be independent of the shock wave speed. The mode of the initial raising of the dust is discussed. Some experiments with dust deposits possessing a forward facing step are described.

Experimental and Numerical Study of Shock Wave Interaction with Perforated Plates

Abstract: The flow developed behind shock wave transmitted through a screen or a perforated plat is initially highly unsteady and nonuniform. It contains multiple shock reflections and interactions with vortices shed from the open spaces of the barrier The present paper studies experimentally and theoretically/numerically the flow and wave pattern resulted from the interaction of an incident shock wave with a few different types of barriers, all having the same porosity but different geometries

Laser-induced iodine fluorescence technique for quantitative measurement in a nonreacting supersonic combustor

Abstract: A nonintrusive optical technique, laser-induced iodine fluorescence (LIIF), is demonstrated in the quantitative study of the compressible flowfield in a steady, nonreacting supersonic combustor. Measurements of density, temperature, and velocity were made with the calibrated technique for two combustor operating conditions. Measurements were first conducted in the supersonic flow over a rearward-facing step for comparison with calculated pressure profiles. The second operating condition was staged, transverse injection behind a rearwardfacing step at an injection dynamic pressure ratio of 1.20. These experimental results demonstrate the capability of the technique for making accurate, spatially resolved measurements of gasdynamic variables in the complex supersonic flowfield. Complete data sets to be generated with this technique will be used to validate computational fluid dynamic (CFD) codes for supersonic combustor flowfields, prior to the inclusion of chemical reaction.

Quasiperpendicular High Mach Number Shocks.

Abstract: Shock waves exist throughout the Universe and are fundamental to understanding the nature of collisionless plasmas. Reformation is a process, driven by microphysics, which typically occurs at high Mach number supercritical shocks. While ongoing studies have investigated this process extensively both theoretically and via simulations, their observations remain few and far between. In this Letter we present a study of very high Mach number shocks in a parameter space that has been poorly explored and we identify reformation using in situ magnetic field observations from the Cassini spacecraft at 10 AU. This has given us an insight into quasiperpendicular shocks across 2 orders of magnitude in Alfven Mach number (M_{A}) which could potentially bridge the gap between modest terrestrial shocks and more exotic astrophysical shocks. For the first time, we show evidence for cyclic reformation controlled by specular ion reflection occurring at the predicted time scale of ~0.3τ_{c}, where τ_{c} is the ion gyroperiod. In addition, we experimentally reveal the relationship between reformation and M_{A} and focus on the magnetic structure of such shocks to further show that for the same M_{A}, a reforming shock exhibits stronger magnetic field amplification than a shock that is not reforming.