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.

Shock Wave Compression of Hardened and Annealed 2024 Aluminum

Abstract: Measurements of the Hugoniot equations of state of hardened and annealed 2024 aluminum at pressures below 50 kbar are presented. The major aim of the experiments was to determine the validity of elastic‐plastic theory, which predicts that, at a given compression, the stress normal to the shock front is larger than the hydrostatic pressure necessary to produce the same compression by an amount equal to two‐thirds the yield strength in simple tension. Oblique shock geometry was employed. Shock and free‐surface velocities were recorded with a streak camera by means of a light‐reflection technique employing the principle of the optical level. This technique provides continuous recording of free‐surface motion with time, an essential requirement because of the existence of a double shock system. The observed elastic wave amplitudes (5.4±0.2 kbar and 0.9±0.2 kbar for hardened and annealed material, respectively) agree within experimental precision with values predicted from static tensile specimen data. The shock wave data, in the range 25–50 kbar, yield one‐dimensional strain isotherms which, while significantly different for the two different hardness conditions, agree within experimental precision with semitheoretical curves based on Bridgman's hydrostatic data to 30 kbar and on simple tension stress‐strain data. No significant strain rate effects are evident. It is concluded that elastic‐plastic theory is valid for the description of plane shock waves in this material.

Supersonic separated and reattaching laminar flows: i. general theory and application to adiabatic boundary layer-shock wave interactions.

Abstract: : The report deals with laminar boundary layer-shock wave interactions in which the pressure rise generated in an external supersonic, inviscid flow is communicated upstream through the boundary layer, and thereby induces flow separation. In order to describe this phenomenon approximately, including the subsequent reattachment of the flow, an integral or moment method is utilized in which the first moment of momentum is employed, in addition to the usual momentum integral (zeroth moment). The theoretical calculations agree quite well with the adiabatic laminar boundary layer-shock wave interaction experiments of Chapman and Hakkinen at moderate supersonic speeds. A comparison between the calculations and the experimental results of Sterrett and Emery on the free interaction upstream of a forward facing step at M = 6.5 also shows good agreement up to the plateau. The highly-cooled laminar boundary layer-shock wave interaction is qualitatively similar to the adiabatic turbulent boundary layer interaction. The limitations of the two-moment method based on a one parameter family of velocity profiles are discussed and the role of a two-moment, two-parameter method such as Wieghardt's is examined briefly.

The impingement of underexpanded, axisymmetric jets on perpendicular and inclined flat plates

Abstract: This paper reports on an extensive experimental study of the flows due to under-expanded axisymmetric jets impinging on flat plates. The range of plate locations extends to a point where the jet is just subsonic but the main emphasis is on the behaviour in the first shock cell. Plate inclinations from 90° to 30° were investigated by means of comprehensive surface pressure measurements and shadowgraph pictures. Wherever possible, the main features of the results have been reconstructed using inviscid analyses of the wave interactions.The flows are shown to be extremely complex due to the local structure of the free jet and, particularly, due to interactions between shock waves in the free jet and those created by the plate. In the near field, these interactions tend to be the controlling factors but at larger distances from the nozzle, mixing effects become increasingly important.The maximum pressure on the plate when it is inclined can be very much larger than when the plate is perpendicular, owing to the possibility of high pressure recoveries through multiple shock systems. Correlations are presented for some of the main features on perpendicular plates and it is shown that the integrated pressure loads for both normal and inclined plates can be predicted well by a simple momentum balance.