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

Shock waves are easily generated in narrow ducts by means of the rupture of a membrane or thin sheet of certain materials. The geometry of the shock waves generated in this manner has been previously described in a qualitative manner using the shadowgraph and schlieren methods. In the present study, the background-oriented schlieren method is used to observe the propagation of a fully-formed shock inside a narrow rectangular duct. In conjunction with measurements of the acoustic signal inside the duct, it is possible, employing the Gladstone-Dale relation, to obtain a two-dimensional portrait of the density field inside the duct. The propagation speed of the shock is also calculated directly from visualization of the shock at different times.