Publications

Development of a Spatially Filtered Wavefront Sensor as an Aero-Optical Measurement Technique

Butler, Luke; Gordeyev, Stanislav; Lynch, Kyle P.; Guildenbecher, Daniel R.

This paper validates the concept of a spatially filtered wavefront sensor, which uses a convergent-divergent beam to reduce sensitivity to aero-optical distortions near the focal point while retaining sensitivity at large beam diameters. This sensor was used to perform wavefront measurements in a cavity flow test section. The focal point was traversed to various spanwise locations across the test section, and the overall OPDRMS levels and aperture-averaged spectra of wavefronts were computed. It was demonstrated that the sensor was able to effectively suppress the stronger aero-optical signal from the cavity flow and recover the aero-optical signal from the boundary layer when the focal point was placed inside the shear region of the cavity flow. To model these measured quantities, additional collimated beam wavefronts were taken at various subsonic speeds in a wind tunnel test section with two turbulent boundary layers, and then in the cavity flow test section, where the signal from the cavity was dominant. The results from the experimental model agree with the measured convergent-divergent beam results, confirming that the spatial filtering properties of the proposed sensor are due to attenuating effects at small apertures.