Calibration of Shock Tubes for Studying Aerodynamic Loading

In a simple shock tube the physical parameters behind the shock cannot be determined from the measurement of a single parameter, such as the pressure, because of uncertainties about the state of the gas in this region. Results are shown which illustrate two causes of this uncertainty: (a) the mixing of the driver and expansion chamber gases, and (b) the variation of the shock strength along the tube. The problem can be overcome by observing the particle trajectories throughout the tube. This is done by high‐speed photography of smoke tracers, and it is shown that the technique permits a determination of all the physical parameters of the flow without reference to other measurements.