Visualization of a shock wave travelling inside a rectangular duct using the background-oriented schlieren method

Abstract

The propagation along a narrow duct of a shock wave generated by the rupture of a membrane is studied by means of visualization using the background oriented schlieren (BOS) method. This optical technique, which has not been used before in this context, is non-intrusive and can be employed to produce a two-dimensional quantitative portrait of the density field inside a section of the duct. Images obtained using a high-speed camera confirm that the shock is, as expected, planar, with boundary layer effects near the interior duct walls observed as well. The quantitative aspect of this method is validated by comparing the amplitude of the shock as obtained from images with direct measurements of the acoustic pressure acquired by means of a probe microphone. Successive images of the shock as it travels also permit calculation of the shock speed.