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Why a dimpled car burns less fuel

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IOL mot pic jun27 Mythbusters dimpled car 2

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It's been proven that a dimpled car has less drag up to a certain speed, which can save fuel. But it ain't pretty.

Cambridge, Massachusetts - The drag-reducing properties of irregular surfaces have been well-known to golfers ever since it was discovered that a dimpled ball could be whacked much further than a smooth one.

Now researchers at the Massachusetts Institute of Technology are aiming to use that same effect to reduce drag on a variety of surfaces, including cars.

The Mythbusters team on Discovery channel proved back in 2009 that a dimpled car used less fuel than a smooth-bodied one, with a one litre per 100km fuel saving recorded at a constant 105km/h.

However, it’s a curious aerodynamic anomaly that while a dimpled surface has half the drag of a smooth one at lower speeds, at higher speeds that advantage reverses.

MALLEABLE SURFACE

So what you’re looking for is a malleable surface whose smoothness can be changed as you’re driving - and that’s what the MIT team has now developed.

They’ve created a multilayer material with a stiff skin and a soft interior - the same basic configuration that causes smooth plums to dry into wrinkly prunes.

To mimic that process, the researchers made a hollow ball of soft material with a stiff skin – with both layers made of rubberlike materials. When the ball shrinks its surface wrinkles – and making the surface irregular or smooth is a simple matter of adjusting the air pressure inside the ball.

The drag reduction of a textured surface isn’t only being used on golf balls.

The soccer ball being used at this year’s World Cup, for example, uses a similar effect; so do some track-suits worn by athletes.

For many purposes, such as in the games of golf and soccer, constant dimpling is adequate.

But for cars, the ability to adjust the texture of its exterior panels to minimise drag at different speeds could increase fuel efficiency.

The only question is: how would you feel driving a car that looks like a golf ball?

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