# Any Wind Tunnel Interest?

I visited the Virginia Aviation Museum in Richmond, Virginia, a few weeks ago and saw a small wind tunnel for public demonstration. That got me wondering if anyone at DMS might find a wind tunnel useful?

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Me! But I may be the only one.

A wind tunnel is big - storage problems.

Also, neighboring members may not appreciate the air coming out of one end.

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I think someone who knows about fluid dynamics and aerodynamics could do a class on computer simulation testing. The way storage has been lately, the more we can do virtually the less that has to be stored IRL

I cannot speak for any other field in fluid dynamics or aerodynamics, but in hobby rocketry, there are two leading simulation programs, RockSim and OpenRocket.

As good as they both are, I can build many designs they cannot simulate.

Jim Barrowman, a NASA engineer, published a simplified method for calculating the centers of mass and pressure of a rocket. But to distill down much of the hairy math, he used some major shortcuts. Both of the simulation programs began with the Barrowman Method.

If there is better simulation software which does not cost an engineerâ€™s salary to license and his degree to be able to operate, I would love to know.

The alternative is to build the model and test it in a wind tunnel for stability. Or use the classic â€śswing testâ€ť: attach a string at the center of mass and swing it around my head to see whether it noses into the wind or turns sideways.

The other measurement is drag. Both programs are notorious for being poor at calculating the coefficient of drag. The way to effectively use the simulation is to build the rocket, fly it and determine how high it goes. Then go to the program, enter the motor used and adjust the Cd until the simulated altitude matches the observed value. That Cd may then used to estimate the altitude of that if different motors are used.

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As you might see in the video, we could make a wind tunnel that would fit within our small area. The one on display was about as long as a file server rack and not nearly as wide. Of course, the size depends on what it is you want to test. The airflow also depends on what you want to test, but I think we could use just a low-speed laminar flow for anything we want to do.

Maybe we could get really fancy and make it a vacuum chamber, too. Then, we could simulate different flight altitudes and get a vacuum chamber out of it.

I know a little about fluid dynamics and aerodynamics and even computer simulation, but not nearly enough to take on a job such as you are describing. In fact, what little I know about simulations is, donâ€™t rely on them for your final design. Simulations are OK for first approximations, but your finished product needs to be tested in physical form.

Such a class was already offered by a member (@ChrisPattison ) and had a decent attendance, though sadly because of the timing I wasnâ€™t able to attend.

That said, simulations are great tools for preliminary screening, but real world testing still reveals problems that simulations do not. Simulations also require some very sophisticated skill sets that are completely different from those needed to design and build most of the objects that need such testing/simulation. They work great for large multidisciplinary team projects, but not really for the smaller projects done at the space.

We can hang it from the roof with the air intake over the plasma cutter, and vent though outside wall! We can have the metal shop build a catwalk for observation and instrumentation.

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