Increments in aerofoil lift coefficient at zero angle of attack and in maximum lift coefficient due to deployment of a double-slotted or triple-slotted trailing-edge flap, with or without a leading-edge high-lift device, at low speeds.
Abstract:ESDU 94031 presents an estimation method based on the theory for a thin hinged plate modified using empirical correlation factors to account for the geometry of practical aerofoils and high-lift devices. Some allowance for the effects of chord extension was made by using flap chord ratio and lift coefficients based on aerofoil extended chord but further adjustments were required to adapt to the considerable departure for slotted flaps from the model, possibly involving large chord extensions. The data for aerofoils with trailing-edge flaps deployed from which the methods were developed were extracted from wind-tunnel tests reported in the literature covering a wide range of practical geometries. Fewer data were available for aerofoils with both leading- and trailing-edge devices deployed. The methods apply to Reynolds numbers greater than a million and freestream Mach numbers less than 0.2. The predicted and test data for the lift coefficient increments correlated to within 15 per cent. The use of the methods is illustrated by worked examples. To obtain results for an aerofoil with both leading-edge devices and slotted flaps deployed, ESDU 84026 is used in conjunction with this document and ESDU 94027.
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