Quote:
Originally Posted by Vman455
I took some pressure readings yesterday for another picture of what's going on. These were centerline readings. First, no add-on spoiler:
Next, with the lip spoiler in place at the top of the window:
And finally, with the lip spoiler at the rearmost edge of the stock spoiler:
The pressure readings decreased by 25-30 Pa over the rear window with the roof spoiler, but pressure increased on the roof ahead by 45 Pa.
Pressure on the window with the edge spoiler varied from baseline by + or - 5 Pa, but again the roof pressure was higher by 30 Pa.
I'm going to do some more testing of the rear lip spoiler today between teaching, with more locations on the window and roof. |
Interesting. But what I'd like to see you do is to use a large spoiler - when pressure testing, I always go for something much larger than I intend using, see the results, and work backwards from there.
For example, we can see that the upper spoiler position increases pressures over the curve at the top of the hatch (from -170 in std from to -125) but puts the rest of the hatch in separated flow (lower pressures than standard) and also decreases wake pressure. So you'd say less lift but more drag.
The spoiler at the base of the hatch increases
average pressures on the hatch, but because the spoiler is so small (and as we saw with the tufting) the effect is also quite small. A 25mm high lip is the smallest I'd ever test in the lower hatch position - I'd start with 75mm and then go smaller in 25mm increments.
So I'd not bother doing any more measurements with these configurations, but go larger in the modification so the effects are clearer. Some of these measurements may be in the range of noise - another reason I start with major changes first. Just use cardboard and tape to make the different height spoilers.