Flow visualization and density measurement of Mach reflection by speckle method

Abstract

The laser speckle method was applied to the density gradient measurement of Mach reflection of shock waves. Density gradient in the internal region behind the reflected shock wave was measured by this method, mainly. A shock tube and YAG laser were employed in the experiment. The reference and flow field images were recorded by a high resolution digital camera. The speckle photographs were processed by cross-correlation method by a computer. Displacement of speckle pattern was converted to the density by using a deflection angledensity gradient relation. The shock pattern was extracted from the intensity difference between a reference and flow field images.