Neuro,

This may sound really extreem, but I have way more ideas than time................LOL

It might be possible to see the wash flow by this method.

Make a 3 sided cardboard box. A refrigerator box should work with the "ends removed". Cut out one side leaving enough to support it from collapsing. Cover the cutout with something clear...saran wrap?
Then, hang an AA in the box at one end. Set up a vid camera here would be nice for a side view. Fire up the AA and then set off a smoke bomb, the ones you see at Walmart and checkout lines..... You might be able to see the wash flow pattern. I think it would show a lot of whats happening and be a great help in yours and others designs.
A cheap wind tunnel!

Just a thought.

Tony
ARS Software & Innovative Solutions
http://www.falcon1.net/~ars/rcmodels.html