Experimental and Numerical Investigation of Shock Wave Interaction with Rigid Obstacles

Introduction

Shock wave interaction with obstacles of various geometric shapes has always attracted attention in a large number of experimental and numerical studies. During the interaction of a shock wave with an obstacle a very complex wave pattern is formed which affects the shock-wave induced flow. The interaction reduces the shock-wave strength and generates rotational flow behind the obstacle. The interaction of shock waves with rigid obstacles is of significant importance in aerodynamic science and other engineering applications. Whitham [1] formulated an approximate theory for the dynamics of two- and three-dimensional shock waves and applied this theory to the description of shock diffraction by wedges and corners. Bryson & Gross [2] broadened Whitham’s theory and applied it to two- and three-dimensional bodies such as cylinders and spheres. They carried out theoretical and experimental work to assess the analytical computations that were made by Whitham. One dominant direction in investigation of shock-cylinder interaction is finding the RR→MR transition criterion. When the shock wave strikes a cylinder, it is reflected as an RR and then transforms to a Mach reflection MR. Major RR→MR transition criteria were summarized and discussed in a scientific monograph by Ben-Dor [3]. Since 1970, due to progress in numerical techniques, very accurate simulations of shock wave propagation over obstacles have been achieved. In most of studies efforts to validate the Euler scheme were undertaken. In the numerical study of Drikakis et al. [4] viscous effects were examined at various Mach numbers during of shock-cylinder interaction by comparing the inviscid and viscous calculations. It was found that the flow field in the downstream half of the cylinder is influenced by viscosity. The main objective of the present study is to better understand the physical elements governing the flow induced by the shock wave and the elements affecting the shock wave strength after passing the obstacle. To carry out the overall research plan two different approaches have been utilized - experimental and numerical. In the present study we focused on the investigation of the reflected shock wave from a single cylinder for low Mach numbers (M _S ~1 − 1.4) in order to characterize the physical factors affecting its propagation. The first part of a broad investigation of the shock wave interaction with complex geometries is presented.