Spanwise Wavefront Analysis of Turbulence Amplification in a Turbulent Boundary Layer Forced by an External Shear Layer.

Abstract

Non-intrusive optical approach was used to study the regions of the amplified turbulence inside the externally forced boundary layer. Spatially-temporallyresolved wavefronts in the spanwise direction were collected and analyzed. The external forcing signal was used to phase-lock the wavefronts. To compare these wavefronts to the phase-locked velocity results, collected earlier in the same facilities, a Strong Reynold Analogy was used to relate the optical wavefronts and the velocity field. The experimental phase-locked wavefronts were found to be quantitatively agree the phase-locked results, predicted from the velocity field. The residual OPDrms was found to be corrupted by the aperture effects. As an alternative approach, local deflection angles, which are insensitive to aperture effects, were analyzed and exhibit good qualitative agreement with the velocity results.