Analysis of Aero-Optical Jitter in Boundary Layers Using the Stitching Method

In the typical analysis of aero-optical wavefront data, the three lowest order spatial modes are removed from the experimental data. These three spatial modes (tip, tilt, and piston) are commonly corrupted by mechanical disturbances. In this work an algorithm was developed that takes advantage of the advective nature of aberrations to compensate for the tip, tilt, and piston removal common in experiment. The algorithm is able to recover the aero-optical component of the jitter and provide time series of global tilt free of mechanical disturbances. This algorithm is called the stitching method. Experiments were conducted in Notre Dame’s Tri-sonic Wind Tunnel (TWT) Facility. Optical wavefront measurements were conducted on a Mach 0.6/0.1 shear layer. Voice coil actuators were placed on the shear layer splitter plate to regularize the shear layer. The predicted results for the RMS of the aero-optical jitter from the stitching method matched well with modeled results. Since the stitching method produces full time series of global tilt, energy spectra were also computed and presented. This information can be used by systems designers to benchmark fast steering mirrors for use in airborne directed energy systems.