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Sunday, November 6, 2011

Wind Tunnel Details

I was sick with the flu this week so I didn't get very much done. I really wanted to do some more experiments with the Plasma Actuator that I wrote about a couple of weeks ago HERE but due to the illness and the cold spell we have had recently I stayed out of the garage. Because of several emails that I have received asking about the wind tunnel, I decided to write a little about the wind tunnel that I built and used for those tests. HERE is the original post that I wrote about building the wind tunnel that has most of the construction details. Below is a picture of the results that I got with the tunnel.
Airfoil Plasma Actuator in my Wind Tunnel
In order to see the airflow I added smoke (fog) to the airstream using a Gemmy Fog Machine. HERE is a link to their website for the model that I picked up at WalMart for about $25.00. The Fog Machine heats up and sprays a mist of glycol and water for about 60 seconds into a heating tube and the result is fog. As the mist is sprayed into the heating tube the tube cools down and the machine stops spraying until the tube can heat up again. I didn't like that so I took the Fog Machine apart and modified it so that it produces fog when I press the button and stops when I release the button. It's always fun to take apart brand new stuff!

After cutting a wire so the fog machine would spray on command I attached a NPT-Tube fitting to the front of it by cutting some metal and screwing the fitting onto the cut metal.

Modified Fog Machine
I added some aluminum HVAC tape around the fitting to cover up the holes you see in the above picture. I added a few feet of tubing to the fitting and attached a TEE to the end. You can see the TEE in the picture below that is feeding the fog into a brass tube that I put in the wind tunnel upstream of the test area.
Wind Tunnel Smoke (Fog) Tube

The TEE is feeding fog into the 1/2" brass tube that has 1/16" holes drilled into it at half inch intervals for the fog to some out in small streams. I used the TEE to get the fog into both ends of the tube so there would be a more even flow of fog from all the holes. The brass tube is lined up with a couple of lasers that have lenses to spread their beams out into a 'fan'. One laser is mounted above the test area shining down and the other is mounted right in front of the fan. The two lasers almost illuminate all the fog streams. Below is a photo of the laser mounted in front of the fan. There is a lot of wood shavings in the wind tunnel from holes that I drilled and I later cleaned out.
Laser in the Wind Tunnel
Laser Locations
The two lasers and lenses illuminate the test area as shown in the picture above. Getting the fog from the brass tube aligned with the lasers was a bit of a challenge but it all worked out in the end. Below is a fuzzy picture of the Plasma Actuator with the lasers turned on. I had the garage light on when I took this picture so some of the areas illuminated by the lasers don't show up as bright (or at all) but you get the idea.
Wind Tunnel with the Lasers

I hope that that this post gives a pretty good idea of what is going on with the wind tunnel and the laser illumination I used to test the Plasma Actuator that I built. As I mentioned I hope to do some more tests with this setup soon. Let me know if you have any questions!


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