This page contains a Flash digital edition of a book.

High-performance thermal barrier coatings, such as ThermoHold from Zircotec, are playing a major part in this particular area of aerodynamic development. Shown here is an exhaust outlet with a ceramic coating

very strange things. The radius and the contact patch changes continuously, and this is a very important aspect in terms of aerodynamics, especially in open- wheel cars. At the base of the tyre there is a vortex created and, if this gets into the diffuser, it reduces its effectiveness. Using the mass flow from the exhaust to drive this vortex away from the diffuser and other critical areas effectively makes the diffuser larger and more efficient.’

COMPUTER SAYS ‘NO’ But to fully understand these flows is a complex challenge, only really made possible by recent technological advances. Indeed, when van Rees attempted to run his first simulations he discovered it required more computing power than the clusters at Cranfield could supply, so he was forced to simplify his model. ‘One of the important things

to remember is that the exhaust is a very high temperature gas flow, and you have to manage

that in the simulation,’ explains van Rees. ‘To do it fully, you have to understand the changes of the properties of the gases. The velocity, density and the thermal conductivity are all influenced so, for me, CFD was really the only way to survey all these factors.’ Van Rees’ simulation was basic by current F1 standards, but nonetheless highly revealing, and he found substantial gains to the aerodynamic performance of the Pilbeam. ‘Just using a very rudimentary design, the MP98’s downforce increased by 11 per cent, and more detailed studies could almost certainly bring greater gains. The drag level also increased but, even so, there was an overall gain.’ With the widely reported change in Formula 1’s exhaust regulations often called a ban on blown diffusers, many of the innovative layouts, such as those used by Red Bull, were outlawed. However, blown diffusers are not banned per se, and the teams are still actively trying to optimise

their exhaust plumes. ‘It is still important, but when you have changes in performance of the order of magnitude that we are seeing with the tyres and getting the tyres to work, it’s not our higher priority,’ explains Ross Brawn of Mercedes. ‘Last year it was one of the predominant performance factors, but this year it is nothing like as significant as it was. I think the cars that came first and second at the Spanish Grand Prix had very conventional exhausts so, unlike last year, the cars with innovative positions are not pulling away from those who are conservative. The range of performance between the solutions is much smaller now. But we still do a lot of work on it, both in CFD and tunnel testing. You can’t do everything in a wind tunnel and, obviously, you cannot generate hot gas. It’s a combination of both that gives the best results.’ Indeed, most modern F1

teams are now working on simulating exhaust flows in the

wind tunnel, but it is notoriously difficult to do, as Giorgio Ascanelli, technical director at Toro Rosso, admitted in pre- season testing: ‘Our simulation capacity is limited in this respect. It depends on the pulse, the speed of exhaust flow compared to the speed of the airflow, the expansion rate, the temperature, ride height, cornering speed and we cannot simulate all of these things with sufficient certainty.’

THE TMG CONNECTION However, some wind tunnels are more advanced in this respect, and Toyota Motorsport GmbH (TMG) in Cologne is a popular destination for Formula 1 teams chasing aerodynamic gains, partly because both of its wind tunnels are capable of simulating exhaust gases, as engineer, Chris Herbert, explains. ‘We have two systems at TMG. In wind tunnel one, we use an air amplifier inside the model connected to a compressed air line. In wind tunnel two, as part of the wind tunnel assembly,

“exhaust is a very high temperature gas flow, and you have to manage that in the simulation”

68 • July 2012

Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80  |  Page 81  |  Page 82  |  Page 83  |  Page 84  |  Page 85  |  Page 86  |  Page 87  |  Page 88  |  Page 89