Quote:
Originally Posted by AeroMcAeroFace
That is quite misleading, for those that haven't read the referenced document, the 5.5% comes from just the wheel and wheel arch drag. And not, as it would appear from Vekke's comment, the whole car.
Considering the frontal area, the drag reduction is, on the scale of the car, very small. How much of the frontal area of a car is tyre? I cannot see comparisons of deflector shapes being able to be measured on the road, far too many variables.
Not just that, being clear with what is actually being quoted is important too, so people aren't misled.
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Did you read it and understood it?
Table 4,1 says it clearly (at least in my opinion):
Total Cd of the whole car 0,216 without any flaps. (body 0,159 + wheels 0,053 + flaps 0) Here is error in chart as the sum up is not same in all of the configurations!
With 40mm flaps Cd 0,204 of the whole car
To my eye it shows 5,55% reduction in whole car drag coefficient is that 5.55%. I put the decimals which are also at the dokument, those who like round ups you can round up to 5,6%->6% or 10% which ever makes you happy. That does not change the flaps in that test changed the whole cars drag coefficient 5,5% better. And again just with front flaps.
Those results mentioned in the test are propably not final and best as the study has been done to automotive manufacturer the best will be something that is not mentioned in the test. That goes to all studies you can find on the internet do they tell everything or do you have to adapt the results to your case or not. I really don`t believe that was the only with and position and width tested for that car as its so easy to test different versions and get better results.
If you take those 60mm flaps wheel drag drops that 18,8% part of the whole car, (0,043/0,053)-1 but the flaps incease drag 0,007 and body drag increases 0,017 giving the whole car drag coefficient 0,215. If and when you design flaps which are more aerodynamic than those vertical plates you can lower you whole car drag coefficient more than 10%. Again my estimation on the savings potential.