19/10/2017

Aerodynamicists: the engineers who want to tear your car apart

Modern cars are beautiful things, but there are people in this world who would like to tear them to pieces, people like Rob Carstairs, an aerodynamicist at Ford.

“The first thing I’d get rid of is the side mirrors. Off they go, that’d be great," said Carstairs. His reason for wanting your side mirrors gone is purely scientific: “They are useless for aerodynamics,” he said.

It isn’t just mirrors that are a thorn in the side for aerodynamicists. In his pursuit of aero perfection, Carstairs would scrap and change a lot of the things we take for granted on modern cars in order to create the most fuel efficient vehicle he possibly can by reducing drag.

The dream for an aerodynamicist is a vehicle that directs the flow of air smoothly all the way over the vehicle, without any disturbances.

That dream happens to look like a teardrop. A teardrop shape allows air to flow smoothly, while the long tail solves the problem of vacuums that are created as air leaves the roof and the trunk. A car this shape would easily be the most fuel efficient on the road.

But there are many reasons why these things aren’t solely left up to aerodynamicists, not least because most people don’t want to drive a car that looks like a giant teardrop.

Fortunately, the final look of a car is the result of the different demands of a number of Ford teams, including designers, aerodynamicists and safety engineers. Safety, of course, is why Carstairs's nemesis - the side mirror - is a non-negotiable fixture on cars.

Compromises like this are a part of the design development process for Carstairs and his colleagues at Ford. The designers know what customers want vehicles to look like, but this isn’t always good for aerodynamics. Likewise, Carstairs can make suggestions based on aerodynamics, but if the vehicle won’t sell then they can’t be used. Because of this, a lot of Carstairs work is done making subtle optimisations which can have a surprisingly big effect.

“Under the front bumper of the Everest SUV we added wings on the outer parts to direct airflow,” said Rob. “It improved aerodynamics by five per cent.”

Many Ford vehicles now also have a slight flick in the tail lamps to stop the air flow from wrapping round the vehicle and causing added drag – an ingenious and mostly cost-free improvement in aerodynamics.’

The work of Ford’s aerodynamicists has been greatly improved by advances in computing.

While wind tunnels are still a crucial part of aerodynamics testing, complex computer models and simulations now allow engineers to easily test design tweaks on Ford’s supercomputer cluster. Rather than replacing wind tunnels, the computer models are an additional measure that can replicate hours of testing that would have been unimaginable ten years ago.

“If we run tests for two days we can easily complete over 50,000 hours’ worth of simulations,” said Carstairs.

The look of a vehicle is also affected by the markets it is destined for. Although lower cars are more aerodynamic, the amount of clearance a car has varies by model, and is also heavily dependent on how flat the roads in a region are.

“In India for example, roads can be a bit bumpier so a vehicle might have to sit a bit higher, we have to consider all the different road conditions across the region.”

However, as more car buyers are demanding fuel efficient vehicles, the design changes suggested by aerodynamicists are being prioritized. “The design team now accepts more and more of our ideas,” said Rob.

In the era of electrification, vehicles are already adopting more aerodynamic shapes. “On an electric car demands for powertrain cooling are reduced, so the grille openings can be smaller,” said Rob. “Things like that are quite handy for us aerodynamicists.”

- driven.co.nz via Ford NZ








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