Affordable schlieren visualization methods for understanding three-dimensional supersonic flows

Abstract: This article discusses affordable schlieren methods which can visualize hidden details in three-dimensional high-speed flow. Mainly, two schlieren methods are brought to light, namely inclined schlieren and focusing schlieren. These two methods have been applied to visualize three-dimensional flow fields like normal shock boundary layer interaction in ducts and flows with shock–shock interactions. The paper explains the possibility of measuring normal shock oscillation in spanwise/transverse direction. Shock height variation across the duct span is also illustrated, using inclined schlieren. Scanning of the focusing schlieren setup can give planar views of three-dimensional shock–shock interactions. It is also shown that the two methods can be merged to give the inclined focusing schlieren method which can also be used to understand three-dimensional flow fields. Further, the possibilities and limitations of these flow visualization methods have been discussed. Graphic abstract: [Figure not available: see fulltext.].