Hello,
I had a brainwave for a passive way of flow attachement with a great angle;
Letting flow stay attached over a surface passively about 17*degrees is the maximum.
Therefor a boattail has to be very long, then I thought of a the way a prius etc. uses a sharp leading edge for clean seperation of the flow.
Vortexes form becouse of the low pressure behind the car.
Vortexes can also be used for sucking in reattaching flow.
Thus a stepped slope would reattach the flow by creating small vortexes.
Then I searched on the web and found some interesting things.
A CFD simulation
323Ci Header/Full Exhaust/CAI/Chipped/3.46:1 Final Drive Build - Page 6 - E46Fanatics
Look at these race mirrors, implaying the same princible.
http://www.racemirrors.com/engineering.html
Look at this hungarian eco car, it's got a slopped rearwindow, exactly what i thougt of.
Antro
EU Transport Research-Fundamentals of Actively Controlled Flows with Trapped Vortices
Attachment browser: Fertis - New Airfoil.jpg by Dickeroo - RC Groups
http://ltces.dem.ist.utl.pt/lxlaser/...ers/11.3_4.pdf
I tried to simulate this with a CFD program on my computer, but as present don't see a change with a normal slope and a tepped one.
I would't love to have more info about this, imaging what's possible you could make a earodynamic side mirror or a rear window and still see enough through it.