Divergent-Trailing-Edge Airfoil Flow

The influence of recirculating flow on drag reduction associated with a divergent-trai ling-edge (DTE) airfoil is provided by comparing the flow structure around a supercritical airfoil with a blunt trailing edge to that around the same airfoil after DTE modification. Flow characteristics are obtained by solution of compressible, Reynolds-averaged, Navier-Stokes equations with a linearized block implicit solution procedure and mixing-length turbulence model. Results show that DTE modification effects an increase in the streamwise length of the recirculation region downstream of a blunt trailing edge that acts like a chordwise extension to increase circulation. The divergent trailing edge gives the same lift at lower incidence and drag, so that lift-to-drag ratio is increased in transonic cruise. Drag creep is reduced by DTE modification because shock-induced drag is decreased as a result of a longer recirculation region in the wake and its associated relocation and weakening of the shock, which is greater than the increase in base drag.

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