Alessandro Bottaro at the University of Genoa has “demonstrated” — in a computer simulation — how fake feathers could take the drag out of flights by reducing turbulence behind an aircraft:
Their synthetic feathers are modelled as rigid keratin bristles 4 to 6 centimetres long and 0.5 millimetres in diameter, coating the cylinder at a density of around three fibres per square centimetre. The cylinder was orientated with its long axis perpendicular to the air flow, placing the synthetic feathers parallel to the wind.As the wind speed increased the bristles started to vibrate in a similar way to real covert feathers, reducing the drag on the cylinder by 15%.
The researchers say that’s because the fibres help to cushion the effects of the air flow on the cylinder itself. Normally the air flows rapidly across the cylinder and creates an area of low pressure behind it. This encourages the formation of strong vortices, creating turbulence and increasing the drag on the cylinder. Racing car drivers exploit that area of low pressure – the slipstream – to stay close to their rivals without having to combat the drag experienced by the car in front.
With the feathers, the low-pressure slipstream does not form, and the vortices affecting the cylinder are weaker. A similar process explains why fresh, fuzzy tennis balls can speed through the air faster than worn ones, says Bottaro.
Similarly, the dimples on a golf ball improve its performance.