[AeroModder]

The induced vorticies likely alter the pressures in different areas.

Package instructions say to position them like this when standing at the rear looking forward:

/ / / / / \ \ \ \ \

That lead to the intensified counter-rotating vorticies and a concentrated area of high pressure at the center of the base of the rear window. The vorticies were strong enough to draw water droplets in the shape of the vorticies.

I tried running with them reversed:

\ \ \ \ \ / / / / /

This lead to two high-pressure areas on the base of the glass:

| x x |

(the vertical lines being the edges of the window and the x's being the high pressure)

That's telling me there's two systems of counter-rotating vorticies, one pair on the outside and one pair in the middle, with the downward directions meeting at the x's. Flow seemed straight on the glass, but I'll need to tuft test to verify. I'm guessing the vorticies weren't strong enough on the surface to affect water droplet flow.

Right now I have them set up like this:

\ \/ \/ \/ \/ /

I'll see what effect this configuration has.