For our Senior Mastery Project my friend and I constructed a Low Speed Wind Tunnel and used flow visulization to observe aerodynmic properties that apply to numerous physics principles. Below is a picture of our Wind Tunnel.
The fan we used was in industrial cooling fan. For visualization purposes, however, we only used the fan on low speed with the addition of a variable speed controller which we wired into the fan's electronics. The speed controller was just a light dimmer switch and allowed full variable speed of the fan. The contraction cone and diffuser were manufactured by a ceiling duct company based on specifications which we provided them with.
Just prior to the test section was a settling chamber with "honeycomb" that eliminated any swirling and turbulent air flow which produced a laminar flow in the test section. We used (a lot) of straws to accomplish this. Below is a picture of the honeycomb section inserted into the test section
The flow visualization method we chose to use was sublimated dry ice. Using a wand, we were able to capture the dry ice 'smoke' when placed in water and direct it to the desired position where the test object was located in the test section. Below is a picture of the smoke trail over an airfoil at different angles of attack.
Below are some videos we took of the wind tunnel testing.