Free-Flight Testing of Hypersonic Edney Shock Interactions

A drop-testing rig has been designed to examine the changing shock–shock interactions between a fixed sphere and a sphere in free flight at Mach 5.0. The flowfield has been examined with two, optical-density gradient based techniques; schlieren and background oriented schlieren (BOS). Optical schlieren captured the six distinct Edney shock interaction types, for three freestream density conditions. Free-flight results obtained through BOS again captured discernible shock interaction changes from the sphere in free-flight. The BOS results suffer from optical blur due to limitations in the optical arrangement, reducing the spatial resolution when compared to the optical schlieren. A brief BOS processing algorithm study is discussed which informed processing of the results. For the BOS configuration in this investigation, the spatial resolution of optical schlieren is superior to that of BOS. Discussions for future improvement of the BOS technique to improve spatial resolution when applied to transient, free-flight investigations are given.