Time-Resolved Wave Front Measurements Through a Compressible Free Shear Layer

Time series of spatially resolved, aberrated wave fronts distorted by propagation through a compressible shear layer are presented. These wave fronts were measured using the small-aperture beam technique (SABT) applied to the compressible free shear layer facility at Arnold Engineering Development Center. Two viewing stations were investigated at the facility, the ® rst directly downstream of the compressible shear layer’s splitter plate and the second at a location 48.3 cm downstream of the ® rst station. The ® rst station was found to have optically active structures of approximately 2.5 cm in spatial extent, convecting at approximately 160 m/s, and inducing rms aberrationsontheorderof0.06waves.Thesecondstationhadopticallyactivestructuresapproximately5cminsize, also convecting atapproximately 160 m/s, and causing distortions on theorderof0.17waves. TheSABTwasshown to be an effective means of measuring high-bandwidth optical wave fronts in a far from ideal laboratory setting.

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