Study on high-resolution Schlieren imaging technique

Abhirami Krishnan

International School of Photonics, Cochin University of Science and Technology, Kochi, Kerala, 682022.

Dr. Srisha Rao M V

Department of Aerospace Engineering, Indian Institute of Science, Bangalore, 560001

Abstract

Flow visualization is an art of making flow patterns visible. These techniques plays an important role in the field of fluid dynamics, providing qualitative and quantitative information and are extensively being used in aerodynamics, engineering, physics, medical sciences, meteorology, oceanography, etc. In case of aerodynamics, the visualization of hypersonic flows (shock and expansion waves) is carried out by Schlieren technique. A typical schlieren system is a grey scale rendering of the line-of sight integrated density gradients in the flow field. Sharp features indicate the presence of shock and expansion waves. Time resolution is of importance due to the high speeds in the laboratory. However, the spatial resolution is adversely affected. There are many fine features like shock interaction that need sufficiently high spatial resolution. The aim of the present work is to modify the current optical schlieren system to enhance the spatial resolution of the image. Additional optical components are used and appropriate calculations are specified.

Keywords: Flow visualisation, hypersonic, aerodynamics, schlieren, shock waves