Soap bubbles to take the drag out of future cars

Soap bubbles filled with helium are helping to improve the fuel efficiency of future cars.

The 3-millimetre bubbles swirl around cars in a wind tunnel. Engineers at automotive research consultants Mira in Nuneaton, UK, use 12 cameras to track the bubbles, and so capture air flows in unprecedented detail (see video, above).

The helium in the bubbles gives them neutral buoyancy: left to their own devices they will neither rise or fall in the air, so any up or down movement can be attributed to air flow around the car.

"There aren't any tools in use today that can give such insight into what's going on in the fluid around a vehicle," aerodynamics specialist Angus Lock, who is leading development of the system, told New Scientist.

Low drag

Consumers are beginning to consider fuel economy and carbon emissions when choosing a new car, says Lock, and so aerodynamics has become much more important to car manufacturers. Cutting a vehicle's air resistance is usually a cheaper way of improving those stats than reworking an entire engine or drivetrain.

For example, although the Honda Prius's hybrid engine helps boost its mileage, so does the car's shape, which creates much less drag than other cars in its class.

The bubble technique is not completely new. It has long been used to see how air moves around a structure: for example, it was used to test models of NASA's space shuttle. But Mira's camera system gives extra insight by capturing the precise movement of individual bubbles in 3D for later analysis and exploration.

Jed Davis