AI traces the aerodynamic price of a taller wing tab

An AI-assisted study published in Scientific Reports on 27 October finds that a tiny tab’s height dominates its effect on an inverted three-element wing.[1]

A small tab changes the flow

A Gurney flap is a small upright tab at a wing’s trailing edge. It changes how the surrounding flow turns, increasing lift. An inverted racing wing directs that lift downwards, pressing the car towards the track.[2]

NASA’s 1988 water-tunnel experiments made the effect visible with dye. Behind the tab, the flow recirculated; along the wing’s upper surface, it could stay attached farther back. The tab effectively changed the airfoil’s camber, its aerodynamic curvature, even though most of the solid surface stayed the same.[2]

The drag response depends on the wing and its operating conditions. The NASA report examined earlier experiments with contrasting drag results. Its own slow-water experiment established a qualitative picture of the flow, at a much lower Reynolds number than those wind-tunnel tests. Seeing the wake explains a mechanism; measuring its performance requires the appropriate operating conditions.[2]

The height sets the price

The new team trained and evaluated a neural network using 800 two-dimensional fluid-flow simulations, then used a genetic algorithm to search four tab configurations. Each was optimised separately for downforce or downforce per unit drag.[1]

For the vertical solid tab, the downforce optimum reached the allowed height of 3.125 millimetres. Relative to the wing without a tab, the simulated downforce coefficient rose 11.24%; the downforce-to-drag ratio fell 6.52%.[1]

Separate wind-tunnel tests of nine geometries found stronger pressure differences with taller tabs; installation angle also changed how the wake persisted downstream. These experiments were not tests of all eight numerical optima. The design choice concerns both force and the flow left behind.[1]

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