DEVELOPMENT AND CHARACTERIZATION OF MACH 2-6 NOZZLE USING HIGH-FREQUENCY OPTICAL AND SURFACE TECHNIQUES

A Mach 2.25 zero-pressure gradient nozzle was designed and machined using computational tools to generate a zero-pressure gradient boundary layer nozzle. The new test section allows optical access and high-frequency probe-based measurements to characterize the boundary layer, including pressure, skin friction, and heat flux measurements.

Furthermore, low and high-frequency surface techniques characterized a Mach 4 to 6 nozzle with an accelerating boundary layer. Schlieren imaging was used to describe the starting behavior of the nozzle in combination with high-frequency skin friction and pressure data. A diffuser was designed and characterized to allow for starting the nozzle at Mach numbers above 4.

Finally, a 40 kHz, sub 1 μsec exposure time-calibrated schlieren was developed and demonstrated with a boundary layer of a Mach 2 accelerating test section. The desired framerate was achieved through the use of high-frequency cameras. The desired exposure time was achieved through the use of a CAVILUX Smart UHS pulsed light source, decreasing exposure time to the range between 10 ns and 30 ns. Applying the calibrated schlieren technique to the turbulent boundary layer generated an averaged image of the density gradient as well as wall normal profiles of the density gradient. A preliminary uncertainty analysis was completed using the calibrated schlieren process.