Remember that if you do make a model (models are always good), that you need to consider the airspeed vs the sizing of the model. Its an L
1V
1 = L
2V
2 thing. For a smoke tunnel, no numbers, just seeing what is attached and unattached.
There are all sorts of dyes and markers that can be used, but if your scoop design is clear, tufts of plain old yarn are very hard to beat. Taped in the middle of each piece allows some great flow indications. That allows you to have that Superman Xray vision view.
However all that said, it seems that 7in^2 is a bit small for the acceleration up to speed, but I am assuming some things about the power level and I did not go back and read the whole thread.
Now I will go back and read thoroughly and see how much shoe leather I just ate.
Regards to All,
HB2