Sanderson Prism Imaging of Shock Wave Impact on Thin Elastic Sheets

摘要

The use of a Sanderson prism is an inexpensive way in which to undertake shearing interferometric studies. Itconsists of a thin plate of polycarbonate material which exhibits birefringent properties when stressed. It isplaced in a rig under conditions of pure bending, and is positioned in a conventional schlieren visualization setup. This results in a series of coloured fringes in the image plane. If a flow of variable density is placed in thetest section the light is deflected from one fringe to another. Images can be generated in both infinite and finitefringe modes.The current preliminary study examines the flow field generated by the deflection and rupture of thin elasticsheets attached to the exit of a shock tube, as a pressure relief device. This is similar to the use of a burst diskconventionally used as a safety device to prevent excessive pressure buildup in a vessel such as impact of ashock wave but differs in that it stretches rather than fractures and thus is less rapid. The use of an elastic membranerather than a metal plate is to establish the potential to reduce the magnitude of reflected waves back intothe system. This paper concentrates on the complex external transient flow, in terms of the shock wave exitingprofiles and flow evolution, the stretching and rupture of the membrane, and the final flow following rupture.