Racing ahead

Written by: Tom Shelley | Published:

Computational fluid dynamics (CFD) is a key technique in Formula One racing – an industry where fractions of a second can be all-important. Julie Bieles reports

Honda is one of the latest Formula One teams to boost its computational fluid dynamics (CFD) capacity – a move that has already had an impact on the track.
The Brackley-based team installed an SGI Altix ICE supercomputer in September 2007 to speed up CFD analysis times. Benefits have included a five-fold increase in the number of complete vehicle CFD models that can be run per week.
“Formula One is a fiercely competitive business where fractions of a second could gain you 10 places on the grid. The rate at which you can develop your car means the difference between winning and ending up outside the points,” says Henrik Diamant, head of CFD at the Honda Racing F1 Team. “The drive for performance is relentless, and with the current technical regulations, aerodynamics is the key area where crucial lap time gains can be made.”
In simplistic terms, he says, “aero gains in race car performance are directly proportional to the number of geometries we can analyse over a given time period”.
Honda uses Fluent as its main CFD solver alongside a number of pre- and post-processing software packages. Existing hardware allowed the team to analyse a few dozen different geometries per week.
“We had recently speeded up our CFD process to such an extent that our biggest bottleneck was the hardware,” says Diamant.
Its old system and the SGI Altix ICE are both running a Linux operating system, which means Honda could transfer all of its CFD solvers, pre- and post-packages and in-house codes to the new platform without having to recompile.
“This ensured that the hardware transition did not cause any interruption to our CFD aero development programme,” he says.
The new hardware has cut the time it takes to run a single case. Diamant says: “Each model requires a fraction of the time to run compared to the old system. This is important if we need to make a last minute modification to the car during a test or at a race weekend.”
Honda’s 2008 season car, the RA108, made its track debut during pre-season testing at Valencia in January – and has already benefited from CFD.
“An undesirable effect of the exhaust gas flow was identified during the first few laps of testing,” says Diamant. “The CFD department immediately ran and analysed a number of complete car cases and delivered a new solution five hours later.”
A new exhaust system was manufactured overnight, and implemented the next day in Valencia. Without ICE, it would have taken days to resolve the issue, says Diamant.
A Honda racing car has about 10,000 components that will be developed over the Grand Prix season. During the year around 20,000 parts will be drawn by the drawing office – which is typically responsible for the car’s mechanical systems including hydraulics, gearboxes and drive train – and a further 30,000 by the team’s aerodynamics specialists.
The CFD team works on every aerodynamically important component on the car –anything that is visible – with some parts, including the front wing, turning vanes, under body, diffuser and rear wing being areas with most performance potential. The team also works on some mechanical systems such as the cooling systems and air intakes for engines.

Changing geometry
“If you look at the geometry of the race car aerodynamically, the car we finish the season with is completely different from what we start with.” Diamant says.
Different parts of the car will be worked on throughout the season.
“For a particular aero update, we might target a new front wing design – in which case we will probably run through a number of CFD optimisations,” he says. “This is fairly automated, which means we could analyse hundreds of front wing geometries in CFD before picking the one with the desired aerodynamic characteristics.”
Diamant says that the new hardware has been operational for six months, but its impact has already been felt on the track – and led to significant cost savings.
“It allows a larger proportion of parts to be developed directly in CFD, reducing the need to manufacture physical components – which saves both time and costs,” he says.
It also gives Honda’s engineers more design freedom, he says.
“With the limited throughput of our old system, our engineers had to be conservative with the numbers of complete car cases they could afford to run on any given project. Now there is now more scope for trying radical new concepts.
“This is not only fun for the engineer, but often yields promising new development directions, which we can then build on with more conventional design programmes.”

Fluid restrictions
The enormous advantages that CFD can deliver to racing teams has led FIA – the sport’s governing body – to limit the use of the technique.
The FIA is concerned that larger teams will have an unfair advantage through their ability to combine CFD with wind-tunnel testing to refine vehicle aerodynamics. The restrictions will limit the number of people involved in CFD analysis and the hardware performance of CFD computer systems.
However, some believe that the restrictions will simply make teams more efficient in the way they use the process.
“We believe that the limitation on CFD and wind tunnel testing will accelerate the trend towards use of CFD tools that accomplish more in less time by integrating simulation with the design process,” said John Parry, research manager for Flomerics – a supplier of CFD software.
“The restriction on the use of CFD acknowledges both the power of CFD and the fact that it has become widely accepted as an essential design tool,” he said.

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