Oblique schlieren image construction from three-dimensional numerical simulations

The experimental visualisation of compressible flows has undergone significant development to the point that a large number of optical techniques exist for extracting both qualitative and quantitative information from these flow fields. However, the visualisation, and importantly, validation, of three-dimensional flows requires further attention. This work details the development of a novel validation tool for three-dimensional compressible flows. Oblique experimental imaging techniques used to visualise three-dimensional flow features in a compressible medium are computationally simulated, and corresponding images are constructed from numerical models. The construction technique can be used to generate images for optical orientations in roll, yaw, pitch and any combination of these. Both shadowgraphs and schlieren images may be obtained, with the latter used in this work. Results are presented as a comparison of constructed images with experimental images and discussed for cases in which a range of features are simultaneously present in a three-dimensional flow field, thus thoroughly examining the applicability of the technique to a flow field of significant importance in gas dynamics research. Graphic abstract