The Use of Shaped Cavities to Improve the Sidewall Boundary Layer Quality in Gas Dynamic Lasers

A series of cavity shapes was tested on the sidewall of a Mach 3 high Reynolds number wind tunnel to determine the effects of the cavity and its downstream lip shape on the external flow. Various mass injection rates into the cavity were provided. Holographic interferommetry, oil flow, and a fast response surface pressure transducer were used to take data. Results indicate that a rectangular cavity with a lip shaped as a short rounded overhang least disturbs the turbulent boundary layer. Low levels of mass injection were found to have little effect on boundary layer quality.