Pattern Recognition in High Speed Schlieren Visualization at the High Enthalpy Shock Tunnel Göttingen (HEG)

Abstract

Time resolved digital high speed image recording of flow properties using schlieren and shadowgraph methods have become a standard tool in today’s investigations of hypersonic flows. Postprocessing is often necessary to enhance image quality, followed by quantitative image analysis to measure important flow features. Therefore, a software has been developed allowing flexible design of evaluation workflows and a high degree of automatization. Evaluation of shock stand-off distance and shock angle in experimental visualization series at HEG can be carried out. Even force prediction based on analysis of model displacement has been realized. The tool and design considerations based on typical problems of hypersonic flow visualization are discussed. Flow image analysis processes and results using a pattern recognition approach known as Hough transformation are presented.