Tipnis, T. J.Finnis, Mark V.Knowles, KevinBray, Derek2014-02-012014-02-012013-08-30Tipnis TJ, Finnis MV, Knowles K, Bray D. (2013) The Aeronautical Journal, Volume 117, Number 1194, August 2013, pp. 771-784.0001-9240http://dspace.lib.cranfield.ac.uk/handle/1826/8232https://doi.org/10.1017/S0001924000008447An experimental study incorporating the use of the Background-Oriented Schlieren (BOS) technique was performed to measure the density field of a rectangular supersonic jet. This technique is easier to set up than conventional schlieren since the optical alignment involving the various mirrors, lenses and knife-edge is replaced by a background pattern and a single digital camera. The acquired images which contain information of density gradients in the flow are solved as a Poisson equation and further processed using deconvolution and tomographic algorithms to generate a 3-D domain which contains information about the actual density. 2-D slices can then be extracted to quantitatively visualise the density along any required planes. The results from supersonic axisymmetric jets are used for validation of the code; these show excellent agreement with pre-validated CFD data. The results for a rectangular supersonic jet are then obtained. These show good agreement with the CFD data, in terms of shock-cell spacing and overall structure of the jet. The technique has proved useful for investigating axis-switching, a phenomenon generally associated with non-axisymmetric jets.en-UKArticle