Navier–Stokes analysis of lift-enhancing tabs on multi-element airfoils

The flow over multi-element airfoils with flat-plate lift-enhancing tabs was numerically investigated. Tabs ranging in height from 0.25 to 1.25% of the reference airfoil chord were studied near the trailing edge of the main element. The two-dimensional numerical simulation employed an incompressible Navier–Stokes solver using a structured, embedded grid topology. The effects of various tabs were studied at a constant Reynolds number on a two-element airfoil with a slotted flap. Both computed and measured results indicated that a tab in the main-element cove improved the maximum lift and lift-to-drag ratio relative to the baseline airfoil without a tab. Computed streamlines revealed that the additional turning caused by the tab may reduce the amount of separated flow on the flap. A three-element airfoil was also studied over a range of Reynolds numbers, with computed results shown to be in good agreement with experimental data.