Oblique shock

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

Experimental evidence for Plotkin model of shock unsteadiness in separated flow

Abstract: Experimental evidence is presented in support of a model of separation shock unsteadiness developed by Plotkin [AIAA J. 13, 1036 (1975)]. Under this model, the position of the separation shock follows linearly damped Brownian motion. The model describes the manner in which relatively broad-band perturbations in the incoming flow lead to relatively low-frequency motion of the separation shock. Close agreement was found between the predictions of the model and the autospectra and autocorrelations of wall pressure fluctuations and shock position fluctuations for several blunt fin flows at Mach 3 and Mach 5. Given the similarity of the power spectra of wall-pressure fluctuations for a variety of separated, supersonic flows, this description may have broad applicability.

Investigation of supersonic phenomena in a two- phase liquid-gas tunnel

Abstract: Homogeneous two-phase flows of dispersed liquid and gas having gas-to-liquid volume ratios around 1:1 exhibit the characteristics of a continuum flow with a greatly reduced sound propagational velocity that approaches 66 ft/sec at atmospheric pressure, and that is reduced further in value as the square root of the pressure. Flows of such mixtures at velocities in excess of the local velocity of sound can produce shock phenomena similar to that experienced in supersonic gaseous media. A supersonic two-phase tunnel was designed and built with such versatility and precision that normal and oblique shock structures can be photographed and analyzed in the absence of boundary-layer interference. The applicability of the isothermal continuum theory to such flows is confirmed empirically for volume ratios near 1:1, and the theory is mathematically extended for both normal and oblique shocks over a wide range of volume ratios centered about the 1:1 value. Auxiliary flow devices were constructed for the measurement of such difficult flow parameters as the relative phase velocity, local void ratio, coefficient of friction, and stagnation pressure. A general change in the flow model matrix was found at volume ratios approaching 1:1. Pressure gradients and relative phase velocities were correlated with the proposed flow models with generally good agreement. The coefficient of friction measured for supersonic flow was found to be a simple function of the local void ratio. Stagnation pressures measured for a wide range of flow conditions approximate an isentropic relation for a substantial part of the lower velocity spectrum. At higher velocities, the stagnation pressure closely approaches the normal shock plus isentropic slowdown theory. Considerable photographic information pertaining to shock structure and phase movement is obtained over the spectrum of flow conditions with Mach numbers ranging from 2 to 20.

Wavelet Analysis of Wall-Pressure Fluctuations in a Supersonic Blunt-Fin Flow

Abstract: Measurements of wall-pressureuctuations in a Mach 3 ¯ ow over a blunt ® n wereanalyzed with the continuous wavelet transform. This technique offers a fresh approach to the problem of inferringow structure from the wall-pressure signal. The time scales associated with large-scale structures in theow turbulence and with shock crossing events are identi® ed as distinct local maxima in the distribution of energy over the wavelet scales. By using the extrema in the wavelet spectrum as a reference, the signal can be ® ltered in the space of wavelet scales to separate the contribution to the pressureuctuations ofow turbulence and separation shock motion.

Bifurcation of a reflected shock wave in a shock tube

Abstract: The problem of shock bifurcation observed for a reflected shock interacting with a boundary layer is investigated both experimentally and numerically. The process has been visualized by means of color schlieren photographs that clearly show the characteristic wave pattern. Accompanying pressure measurements hint at the three-dimensional character of the wave system. In a numerical scheme based on the Euler equations the problem has been simulated giving good agreement between the calculated and the observed wave configuration.