Abstract
Laser speckle method is a well known technique that is useful for both visualization and quantitative measurement. This technique was applied to the density measurement of Mach reflection of shock waves in the present experiment. The Object of the measurement is the density field of simple Mach reflection in relatively low shock Mach number. The non-uniform flow field is divided into three regions by incident, Mach and reflected shock waves. A shock tube was employed in the present experiment. Wedges of 20 degrees and 45 degrees were placed in the test section. YAG laser was employed as a light source. Speckle photograph was taken by a digital still camera. Simple subtraction between the reference and flow images shows a shock pattern and a degree of the correlation of speckle pattern in the flow field. Thus, we can obtain a visualized flow image showing a configuration of Mach reflection from speckle photograph. Speckle photographs which was obtained in the experiments were processed with cross-correlation method. A reconstructed density gradient vector map of Mach reflection was obtained. Comparing the experimental result with numerical one, the measured density gradient shows a good agreement with theoretical prediction.
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Hiroyuki Hirahara: He received his Master of Mechanical Engineering degree in 1983, and his Doctor of Engineering degree in 1986 in Kyushu University. After the DE course, he worked in atomic power plant engineering section in Toshiba Co. Ltd. He worked as an Research Assistant and a Lecturer of Saitama University, before taking up his current position. He is an Associate Professor of Saitama University, and his research subjects are high speed flow, supersonic flow with condensation or evaporation, flow measuring techniques, optical measurement techniques and environmental fluid mechanics.
Masaaki Kawahashi: He received his MSc(Eng) degree in mechanical engineering in 1968 from University of Electro-Communication, and his D.Eng. in 1978 from the University of Tokyo. After MSc he worked as a Research Assistant, a Lecturer, and an Associate Professor at Saitama University before taking up his current position as a Professor at Saitama University. His research interests in thermo-fluid phenomena induced by finite amplitude wave motion in ducts, speckle metrology, and PIV measurement of complicated flow field like in centrifugal fan.
Atsushi Murayama: He received his master degree in mechanical engineering from Saitama University. He works at Kanto Auto Works Ltd.
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Hirahara, H., Kawahashi, M. & Murayama, A. Flow visualization and density measurement of compressible flows by a laser speckle method. J Vis 2, 395–402 (2000). https://doi.org/10.1007/BF03181454
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DOI: https://doi.org/10.1007/BF03181454