Computational fluid dynamics is helping Formula 1 motor racing teams get an edge as they attempt to develop faster cars within increasingly tight rules. It is also evolving to help building designers as they attempt to develop more efficient designs for tall structures.
More from: F1 technology advances tall building design
Compare the 1996 F1 World Championship-winning Williams-Renault with a 2016 Mercedes or Ferrari, and a strong family resemblance is obvious.
By 1996, the days of radical, ground-breaking F1 design changes were over. There were to be no more six wheeled cars, or side skirts, or “fan cars”. Designers were limited to a much more restrictive palette by the regulations, and so the cars they produced all tended to follow the same basic pattern, and F1 evolution slowed dramatically.
The 1996 cars and today’s machines sport wings front and rear, with cooling radiators in sidepods and engine air intakes above the driver’s head. The two decades of development that separate them from today’s cars, can, however, be seen in the details.
Whereas the wings and ducts on the Williams-Renault are simple and straightforward, the 2016 cars are also adorned with a complex array of subtly sculptured wings, endplates, ducts and vanes. Each design team strives to achieve ever greater aerodynamic efficiency, to minimise drag and maximise downforce and extract the full potential of the chassis and engine.
Such effort is understandable. There can be less than two seconds difference in lap times between pole position and the cars five or even seven ranks back. At the front of the grid, the difference between the top two cars can be measured in hundredths or even thousandths of a second.
Achieving the optimum aerodynamic package is an expensive business. Full size cars can now be tested in a wind tunnel equipped with a sophisticated “rolling road” – at a cost of £50,000 a day. Even testing a half scale model can cost upwards of £20,000 a day.
Then, just one day on a test track to validate the wind tunnel results can set teams back a cool £100,000.
Regulators have attempted to level the playing field between the lavishly funded top teams and those on tighter budgets by placing limits on wind tunnel and track testing. As a result, the use of computational fluid dynamics (CFD) as an alternative to real world testing has blossomed.
CFD as a concept originated way back in 1910. It models the interaction between fluids and surfaces under a range of conditions and to varying degrees of accuracy. By the 1990s developments in computing power and analytical methods made the technique applicable to aircraft, ships – and race cars.
A CFD analysis begins with the geometry of the surface being established by CAD techniques. Then the volume of the fluid to be considered is divided up into discrete cells – this is ‘meshing’. The smaller the cells the greater the accuracy of the final analysis.
More parameters are entered, boundary conditions defined. Calculations are carried out iteratively, then the results are displayed and evaluated.
Twenty years or so ago a single CFD analysis of a racing car design could take weeks, and even then would not be particularly informative. But computing speed has developed exponentially. Software tools have also become massively more powerful. Nowadays designers can go straight from a CAD proposal to a CFD analysis, and run many variations on the theme in a few hours.
So successful is the technique that more and more resources were poured into CFD analyses. Again the regulators stepped in, imposing limits on expenditure and computer use. Now CFD is a standard tool for the design of a wide range of competition cars besides Formula 1 – sports cars, Indycars and more. In practice it has at least two advantages over wind tunnel testing, apart from the lower cost.
Wind tunnel testing can never reflect the real world with 100% accuracy due to the effects of the indispensable mounting points needed to secure the car on the rolling road. And there is no way it can reproduce the aerodynamic interference from other cars in close proximity.
With cars so little different in performance terms even the relatively small volume of air passing through the front brake cooling ducts can have a significant effect. The complex flows through the many ducts, filters and radiators are almost impossible to visualise in the wind tunnel, but CFD can provide valuable insight and understanding.
F1 Tall Buildings London
Other classes of vehicle are now feeling the benefits of CFD analysis. Vans and HGVs may soon be sprouting turning vanes and sophisticated air deflectors in the search for lower drag and greater fuel efficiency. And few manufacturers of passenger cars ignore the potential of CFD.
Applying CFD to tall and supertall building design carries with it the promise of improved and more efficient design, of structure and cladding alike.
Wind has always been the most unpredictable factor in the design process, and as tall buildings rise up in ever closer proximity to each other and as their architecture becomes ever more individual, more extreme, then the need for reliable data on wind effects becomes ever more pressing. CFD would seem to be the solution to many problems.
How F1 testing aids super tall building design