Blast Wave Patterns : 2011

Photograph by

Phred Petersen

About this image

High speed schlieren image showing the propagation of a shock wave from a toy cap gun charge inside a cylinder. This technique visualises changes in the refractive index of a gas, in this case because of changes in air density. The charge is ignited in the upper left frame. By the frame at upper right the spherical shock wave is well developed. At lower left the principal shock wave has been completely reflected from the corrugated interior surface of the cylinder causing a complex pattern of interactions. In the last frame the interactions have largely resolved into a near-spherical principal reflection. The frames were captured at a rate of 5000 per second with a synchronised flash unit providing exposures of 25 nanoseconds. The elapsed time between first and last frames was just 0.6 milliseconds. The video was captured with a Phantom v7.3 high speed camera and HSPS Mini Strobokin flash unit. School of Media and Communication, RMIT University, Melbourne, Australia