Numerical simulation of shock wave and contact surface propagation in micro shock tubes

Micro shock tubes have been widely used in many engineering and industrial applications, but their performance and detailed flow characteristics are not well known. Compared to macro shock tubes, unsteady flows related to the moving shock waves in micro shock tubes are highly complicated due to more active viscous dissipation and rarefaction effects. This makes shock wave dynamics significantly different from theoretical predictions. One of the major flow behaviors related to the shock wave propagation in micro shock tube is that the boundary layer growth leads to stronger dissipative shock wave. Due to effects of the scale, more shock wave attenuation happens in micro shock tubes. We used a CFD approach to understand the flow characteristics in a micro shock tube with finite diameter. A fully implicit finite volume scheme has been employed to solve the unsteady compressible Navier-Stokes equations. The diaphragm pressure ratio and diameter of the shock tube were varied to investigate their effects on micro shock tube flows. Based on the predicted results, some wave diagrams were built to characterize the micro shock tube flows. Detailed flow structures between the contact surface and moving shock wave were analyzed during the present study.