[elhigh]

Back in the day my brother, dad and I built a small wind tunnel for my brother's science fair project. It used a box fan, a convergent section, and an observation section where the test piece went on a small, homemade balance scale. The weights for the scale were on the downwind side, but in retrospect it would have been much better to have them outside the chamber entirely.

It was a step up from a kitchen table top, but the investment in it was some cardboard and green paint. Looking back I think the paint was very, very close to Matthias Wandel Green.

The wind tunnel's test section was about 8" x 8" x 12", and its design was for measuring differences of lift in wing sections based on airfoil profile and angle of attack. We drew up plans for how to measure drag using a small spring scale, but time got short and that aspect was shelved. Even without that, we were able to quantify our results and compare them to known attributes of the various profiles we tested, and our numbers more-or-less lined up with the stated facts. As experiments go it wasn't anything groundbreaking, but if nothing else it pointed up that we could get good results with minimal equipment. For quantifying the lift of the wings, we used pennies as counterweights.

My point is that Tugger, though a bit condescending, isn't wrong. You don't have to have the big expensive facility to get scientifically valid results. An incense stick and a contrasting background WOULD be excellent for viewing where the flow breaks.

The only trick here would be making really good models so what you test at the tabletop scale translates usefully into real world applications.