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Project Sierra, AKA the desktop wind tunnel, has been something I have wanted to create for a very long time. Although most desktop wind tunnels are used as more of a novelty item nowadays, I wanted one that would assist me in rapid testing and validation for future projects.
The issue with desktop wind tunnels is that, as the test chamber is much smaller, even small discrepancies on the inner wall of the test chamber can cause a change in test results. After doing a lot more research on wind tunnels and automotive wind tunnels in particular, I was able to identify the 4 main sections in a wind tunnel, namely:
1. The stabilisation section- This section is to ensure the air entering the wind tunnel is laminar.
2. The contraction section- This section pressurises the air by reducing the cross section and leads into the test chamber, which speeds up the air in the process.
3. The test chamber- This section is where the test object is placed and typically has ways to observe the air interacting with the object.
4. The diffuser section- This section is meant to relieve pressure that would have been built up in the contraction section; however, based on my research in automotive wind tunnels that do not resurcate the air, it isn't completely necessary.
For the electronics, I decided to take a very simple approach. I used the largest PC fan I could find on the market, which would run at a decent RPM and produced less than 12db of noise. The reason I took the noise into account is that noise is produced based on the behaviour of the fan blades and the number of vortices generated by the blade tips. Therefore, a fan that would produce less noise was likely to provide a more streamlined flow of air into the test section. As seen in my sketch above, the fan was connected to a DC-DC regulator, which was connected to a steady power source.
The image you see on the left is when I tested the airflow the fan produced, by burning an incense pod in front of a test object.
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