Computed-tomographic density measurement of supersonic flow field by colored-grid background oriented schlieren (CGBOS) technique

The background oriented schlieren (BOS) technique is one of the visualization techniques that enable the quantitative measurement of density information in the flow field with very simple experimental setup. The principle of BOS is similar to the conventional schlieren technique, which exploits the bending of light caused by refractive index change corresponding to density change in the medium and both techniques are sensible to density gradient. In this report we propose colored-grid background oriented schlieren (CGBOS) technique. The experiments were carried out in a supersonic wind tunnel of test section size 0.6 × 0.6 m² at JAXA-ISAS. A colored-grid pattern was used as background image and density gradient in vertical and horizontal direction was obtained. Computed tomographic reconstructions of 3D density information of the supersonic flow field around an asymmetric body from multi-directional CGBOS images were examined.