Computer simulation is ovenight success

WilliamsF1 has been at the leading edge of computer-aided design and manufacture (CAD/CAM) for nearly three decades, but its latest project has eclipsed all that has gone before. The team has been under pressure for the last couple of seasons in the FIA Formula One World Championship – although, with the new regulations and innovations across the grid, competition was much tighter last season, with the championship finally being claimed with a less than emphatic eighth place by Michael Schumacher. To wring extra performance from its chassis, WilliamsF1 turned to computational fluid dynamics (CFD) and Hewlett-Packard to help maximise its aerodynamic advantage. The trick to aerodynamic development, if there is one, is lots of hard work – lots of wind tunnel testing, lots of simulation and lots of track testing when you can get track time. In order to feed the voracious appetite of a Formula One wind tunnel you have to have a very good idea of what's happening aerodynamically on the car, so that you only make and test those components that are likely to make a positive contribution. This is where CFD comes in. With CFD you can weed out the crazy ideas relatively quickly from the potentially more productive ones. The result: the parts you put on the wind tunnel model actually make a positive contribution, and you can use the tunnel test to fine tune them. But if you're doing lots of wind tunnel testing you're doing even more CFD simulations. And in order to make CFD a viable part of the process you have to have very fast throughput. This is where HP, WilliamsF1's long-term technology partner, comes in. WilliamsF1 is no stranger to complex CFD analysis, and in the recent past it has used a succession of high performance computers in order to reduce the simulation turnaround time. "The turnaround time is critical for us," says Alex Burns, general manager at WilliamsF1. "What was happening with the HPC 320 [its old supercomputer] was that it was taking typically 36 hours to turn around specific CFD analyses. So if you started a job on Monday night you got the results back Wednesday morning, which was not really conducive to rapid aerodynamic development! "With our new machine, the HP ProLiant Cluster, if you submit a job Monday night you get the results back Tuesday morning – which marks a real step change in productivity for our aerodynamic development. At the same time we've also substantially increased the size of the models that we're putting through, which allows us to become more accurate as we refine mesh sizes in key areas." Top 500 compute engine So what is a ProLiant Cluster? In the WilliamsF1 case the system consists of a number of Intel Xeon-based servers running under Linux. These machines are arranged in racks with very fast communications between them and access to a large amount of shared storage. WilliamsF1 is characteristically cagey about how many nodes are joined together in the cluster, and the team is even shy about mentioning the details of the software components, although everything is commercially available. It is prepared to say that the machine ranks amongst the top 500 computers in the world in terms of raw speed. This gives an indication of the magnitude of the competitive advantage that WilliamsF1 believes it has with the technology. It would take a competitor some time to make up the technical ground, but WilliamsF1 is not keen to offer anyone a free head start in duplicating its installation – and rightly so. "This is the first time HP has assembled a Linux cluster of this magnitude," says Burns. "Everybody close to it has been surprised at how well things have gone, in terms of the speed for the implementation, the rapid turnaround of simulations and the accuracy and repeatability of the results. It's been a real 'Linux comes of age' experience and it's a real positive indication of the potential for Linux in a mission critical technical environment. Powered up and open "It was a big decision to move away from proprietary operating systems onto Linux on something this complex… We moved from Unix to Linux purely because of price/performance. This allowed us to have an affordable solution, which gave us overnight turnaround. It would have been possible using Unix, but prohibitively expensive. We've found Linux to be stable enough and reliable enough for our purposes. Given the increase in speed that we've achieved, having the occasional job that has to be re-run is better than having a slower machine for everything we do." According to Naethan Eagles, senior CFD aerodynamicist at WilliamsF1: "CFD is actually the catalyst for the design solution – with the visualisation of the CFD you are so much more aware of what is going on that it is the inspiration for much of the aerodynamic development. CFD is actually leading the design process." In fact, WilliamsF1 has been using CFD as a design tool – as opposed to a checking tool – for quite some time. It plays a multi-functional role: it provides inspiration and it is used to pass data to other departments, like structural loads. "If we're checking an individual component we would analyse up to 30 different variants to find the optimum," says Eagles. "This can be coupled to a machine for iterative optimisation, which would do maybe a hundred iterations." Since the team joined up with HP more than four years ago, its analysis capabilities have increased significantly. Dynamic structural analysis is 20 times faster and CFD simulations are 100 times faster. "And we're still working to push these rates higher," says Burns. "The fact that things happen quicker doesn't mean anybody goes home earlier; it just provides extra capacity for doing more iterations. The big step we made this year in CFD is getting to overnight capacity for a whole car model." Also, WilliamsF1 has not reduced the amount of physical testing it does. One of its engineering objectives is to increase the amount of tunnel time the team uses, and it is currently building a second wind tunnel at its Grove site to achieve that. But as a consequence of the faster, more accurate CFD solution, the aerodynamicists and engineers have a lot more confidence in the parts that make it to the wind tunnel. This produces a higher success rate in the tunnel, which allows them to bring development parts to the car a lot more quickly. "What WilliamsF1 is doing is not unprecedented but very close to it in terms of the fidelity of the models that it's running, and the turnaround times that it's getting from them," says Dr Tim Bush, engineering segment manager, Hewlett-Packard EMEA. "It's really a story about teamwork and partnership more than anything else. The sideline to this is that the system was installed in May 2003 and WilliamsF1 saw some benefits before the end of the 2003 season. The team is now launching its new car. This is the first time it has been able to design the new car with the benefit of this technology, and I think they're expecting great things from it." "We're expecting substantial improvement from the new car," confirms Burns. "Having this new system in place has significantly reduced the turnaround times for the analysis and has made a substantial contribution to increasing our rate of development." Competition was much tighter last season, and WilliamsF1 raised its game when it really mattered, thanks in part to this new technology. Maybe it's just what is needed to make the difference in 2004 – and not just in F1. Watch this space.