I did some more testing of the A pillar on the Insight. I have also in this post summarised the testing I have done previously.
As standard, the window behind the A pillar shows some interesting tuft patterns. There is obviously some separation but I also wonder if this is not the base of a vortex.
Measuring pressures on the side of the car showed a significantly lower pressure on the forward part of the side window, again perhaps indicative of the base of a vortex.
In an attempt to get better flow attachment, I have tried two different types of vortex generators (Stolspeed and small rubber wedges) mounted on the A pillar, but couldn't see a lot of improvement.
Best improvement in flow pattern came from using an aerofoil turning vane. (A turning vane made from curved flat sheet didn't work.)
The length of the turning vane is dictated by the length of the aerofoil (taken from a small vertical wind turbine).
If in fact the pillar/window interaction was causing the development of a vortex, I thought that perhaps measuring the pressure on the side glass with/without the turning vane may show a significant change.
- 80 km/h
- two way average
- Dig manometer
- Pitot tube ref at 2.2m
- 12 degrees C
- light/moderate winds
No vane: -169 Pa
Vane mounted very high on the pillar: -197 Pa
Vane mounted high on the pillar (as shown): -141 Pa
Vane mounted middle on pillar: -182
Vane mounted low on pillar: -199 Pa
Re-test of vane at high position: -141 Pa
So the vane in its best position (and that was the best position when looking at flow tufts too) increased pressure by about 17 per cent. Note though that the pressure has not been increased to anywhere near the typical pressure down the side of the car (about -100 pa). I assume from this that the vortex (if it is one) is still quite strongly present.
So I don't think that is sufficient improvement to keep the modification.
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