Improving flow behind side mirrors
 

Small rubber door stops...

https://i.postimg.cc/dVfHzm4t/door-stops.jpg

...cut up...

https://i.postimg.cc/022VjH4y/IMG-0302.jpg

...to form small vortex generators.

https://i.postimg.cc/0Qsfstmx/IMG-0446.jpg


Placed between mirror and door on W212 Mercedes...

https://i.postimg.cc/qv6XCfx4/IMG-0431.jpg

...and tuft tested.

https://i.postimg.cc/SK0L6Zg8/IMG-0435.jpg

Whiteboard marker used on glass to show tuft behaviour.

https://i.postimg.cc/V6gjczmB/IMG-0439.jpg

Solid lines show arcs within which tufts were moving without VG. Dotted lines show behaviour after VG - much steadier, showing better flow attachment. Note also the better flow direction.

So I don't think that this would give a reduction in drag even remotely able to to be measured. However, nice to achieve better flow attachment at basically zero cost and effort.

I also think that in some cars, there should be a noticeable reduction in aero noise. (Not on the Mercedes, though - it has thick glass.)

Without and then with.

https://i.postimg.cc/GpcLkP0z/little-VG-compared.png