A First Experimental Approach to the Distributed 3D-Vortex Receptivity of a Boundary Layer on an Airfoil
STUTTGART UNIV (GERMANY) INST FUER AERODYNAMIK UND GASDYNAMIK
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This paper is devoted to an investigation of the distributed linear receptivity of a two-dimensional laminar boundary layer on the curved surface of an airfoil with respect to non-stationary free-stream vortices. The vortices represent a periodic anti-symmetric vortex street localized along the spanwise coordinate with the vorticity vector directed initially i.e. upstream the airfoil perpendicular to the flow velocity vector and the leading edge of the airfoil. The vortex-street frequency was chosen to be close to flat of the most amplified 2D TS-wave. Hot-wire measurements were performed as a set of spanwise scans which cover a part of the streamwise region of the continuously excited 3D TS-wave train. Due to different phase speeds of the outer disturbance and the TS-waves this wave train is found to be modulated in spanwise and streamwise directions. Using a phase-locked measurement system the complex TS-wave amplitude is determined at the maximum of the TS-eigenfunction inside the boundary layer and Fourier decomposed into spanwise wavenumber spectra. In a similar way the complex amplitude of the free-stream vortices is determined as a reference.
- Fluid Mechanics