Desktop Wind Tunnel

Inspired by Windsible, I built a desktop wind tunnel for 1/43rd scale model race cars. I use it to visualize the flow of air over them with a small smoke machine - Im not looking to take measurements off of it (yet!)I went through a bunch of iterations on this - initially I had contraction / expansion cones at each end, but I couldnt get a stable (laminar) flow through the tunnel, so I dropped those and packed the inlet with drinking straws to prevent minor disturbances outside the tunnel from introducing instability inside, Then I had a problem with pulses from the pump in the smoke generator - so I buffered the smoke under the road, letting the low pressure in the chamber suck it out - this produces best results, damps out the pulses from the pump in the smoke generator and giving you nice clear smoke lines.Finally I added a HEPA filter before the fan - it does introduce some blockage, but allows you to run the smoke without filling up the room and setting off the fire alarms.Its bes