TECHNOLOGY – AEROBYTES
Figure 3: the effect of the 2012 modifications on total downforce
Figure 6: the effect on the ‘baseline plus engine cover fin’ specification of increasing the ride height
Figure 4: the effect of the 2012 modifications on aerodynamic balance
Figure 7: the effect on the ‘baseline plus fin and wheelarch aperture’ specification of decreasing the ride height
evaluation they made the cars less aerodynamically efficient, with less downforce and more drag over a typical working yaw range. This would obviously decrease corner speeds as well as straight-line speeds, unless the teams come up with ways of mitigating the losses.
Figure 5: the effect of the 2012 modifications on drag
configurations being slightly wider at six degrees yaw. But in truth, the balance shift resulting from the mirrors was modest.
2012 SUMMARY So what was the overall effect of the mandatory-for-2012 engine cover fin, wheelarch openings and larger mirrors? Figures 3-5 illustrate. Total downforce was reduced
across the whole yaw range, by between 3.4 and 5.1 per cent
www.racecar-engineering.com • Le Mans
at six degrees and zero degrees yaw respectively. In terms of aerodynamic balance, this shifted rearwards across the yaw range, though the effect of yaw on the 2012-spec car was greater, with the ‘%front’ value higher at six degrees yaw than at zero. And drag was higher too, between 2.1 and 2.6 per cent at six and zero degrees yaw respectively. So whatever else the 2012
modifications were intended to achieve, on the basis of this
MORE TALES OF YAW We’ll end this project with another look at why evaluating each configuration across a working yaw range was such a useful exercise. Part-way through the session it was decided to try raising the car’s ride heights, (10mm front, 15mm rear). The engine cover fin had already been installed but, after raising the ride heights, the wheelarch apertures were opened up and the car was lowered to the standard ride heights again. Figures 6 and 7 show the different total downforce plots. Clearly, the responses of
the car across the yaw range in the two different specifications
were different but, had we been testing each configuration in the straight-ahead position only, then in figure 6 we would have seen that overall downforce decreased as the ride height increased, which would have been expected and would not have been questioned. What was surprising is that at six degrees yaw the total downforce had not in fact decreased, although the balance had shifted rearwards. Conversely, in figure 7
it would appear that in this configuration in the straight- ahead position, re-setting the ride height from its raised level to its standard height made almost no difference to total downforce (though once more there was a balance shift), yet at six degrees yaw, downforce did increase as the ride height was reduced again. Hence, the value of the additional data collected is abundantly clear.
Racecar Engineering’s thanks to Greaves Motorsport.
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