Experimental verification of the mach-number field in a supersonic Ludwieg tube

The detailed Mach-number and flow-direction field were analyzed by using the method of visualization of Mach waves. The method was useful in plane flow because weak plane waves were very easily detectable by line-of-sight integrating methods such as schlieren or shadowgraph techniques. It was found that the leading and trailing shocks off the adhesive tape diverge significantly at the upstream end of the nozzle, where the boundary layer is thin. It was also observed that the divergence decreases rapidly farther downstream as the boundary layer thickness increases and the Mach number gradient decreases.