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Dual wavefront sensing design for supersonic wind tunnel experiments

Departmental News

Posted: November 7, 2018

Date: Friday, November 09, 2018 

Time:  1:00 PM

Location:  CHTM, Room 103

Map to CHTM:

Parking passes are available at the receptionist desk.  The CHTM building is equipped with ADA accommodations as well as parking spaces.

Speaker: Mr. Cameron Rodosevich

The Air Force Research Laboratory (AFRL), Directed Energy Directorate has constructed a supersonic wind tunnel in order to characterize aero-optical effects impacting airborne systems. A key part of this project is to build the instrumentation and develop the corresponding models to characterize the flow distortion generated by the test articles placed within the wind tunnel. In the past, aero-optical measurement techniques within the wind tunnel environment were primarily based on the Shack-Hartman wavefront sensor (SH WFS) and Schlieren imager. However, using these techniques one cannot separate the aero-optical effects due to the formation of boundary layers near the windows (required for optical access to the tunnel) from those generated by the test article. As such, the additional optical aberrations generated by the boundary layer act as a source of noise in these measurements.

My internship project has comprised the design and building of a more advanced optical diagnostic system for AFRL’s wind tunnel. In addition to a SH WFS and Schlieren imager (serving as the baseline aero-optical measurement tools), our system includes a digital holography wavefront sensor (DH WFS) that has the potential to separate noise from the signal and effectively enable extraction of the wavefront deformation at desired locations within the wind tunnel. The DH WFS is a novel and unique approach within the wind tunnel environment, capable of providing an estimate of the complex-optical field.

This presentation reviews the optical system design, principles of operation, and construction of this dual wave-front sensor aero-optical diagnostic system. I will also present my preliminary measurements as well as an introduction to methods and models that I aim to develop to numerically back-propagate the measured complex optical field to various planes within the test section, and separate boundary-layer aero-optics from those of a test article.