Shock wave curvature close to the shock tube wall

Some theoretical curves calculated for the curvature of a shock wave at the wall of a shock tube at low initial gas pressure are compared with some experimental results obtained on this phenomenon. Data from different workers can be seen to fit reasonably well with curves calculated using different approaches, such as the continuum approach or by accounting for slip at the wall, but not all data fit all curves. Some problems in investigating the interaction region between shock wave and the beginning boundary layer are briefly discussed.