Planar Wave Propagation In Shock Tubes For Replicating Blast Injury

To replicate clinically relevant blast trauma, shock tubes are often employed. One key assumption in the use of compressed gas or explosive driven shock tubes is that the shock wave output is planar no matter what the cross section of the shock tube and a fully developed shock wave is impinging on the test subject. The current investigation examines the effect of tube cross sectional shape and tube length on flow evolution and shock development to better understand design constraints and limitations when using shock tubes. Three dimensional arbitrary Lagrangian-Eulerian shock tube models were developed and simulated at physiologically relevant burst pressures of 2.32, 4.65, and 6.97 MPa. Results show that planarity develops in a round cross section after approximately 7 diameter lengths down the driven section of the shock tube for the lowest burst level and after 5 diameters lengths for the highest level. Oscillatory off-axis waves are damped by destructive interference in the axisymmetric round cross section. Such damping did not occur in the square shock tube, which continued to show deviation up to 59.6% from planarity even at ten diameter lengths.