What Engineers Do When They’re Not Working: Tornado Wind Speed Experiment

We’ve written about the extreme power of winds during a tornado before, especially about the phenomenon of how these forces can drive a very lightweight object into – and often all the way through – another solid object.  Recently, a couple of our engineers attempted to recreate this type of incident in the lab by propelling a small, lightweight object through another solid piece, and studying what happens when the propelled object builds enough force to pierce a sturdy material (in this case aluminum siding).

We performed eight tests utilizing a cannon built by Pie’s engineers. The cannon included a pneumatic system capable of firing projectiles ranging in diameter from ½ inch to 4 inches in width. During the experiment, the air pressure of the cannon was calculated between 20-135 psi (speeds between 100mph and 176 mph) and was filtered using a 1 inch, 24 volt electric solenoid.

Earlier tests involved propelling a stainless steel lightweight water bottle (Go Mustangs!) and a pop can.

The latest tests…well, you can see that in this video:

[youtube=http://www.youtube.com/watch?v=WS0iskYan7Y]

The results were the most interesting part of the process:

2012-03-27_11-47-52_495

 

 

 

 

 

In the obvious ways that a tornado creates destruction, the results became the same for us…when small objects, even very lightweight, are propelled at high speeds, they can do an incredible amount of damage when they hit something, even something that seems impossible to penetrate.

In one of our earlier articles that addressed this phenomenon, we quoted an expert who compared it to someone jumping into a body of water.  The faster you fall, the less time the water has to get out of the way of the person hitting the water, producing more fatal results.  Likewise, the faster an object hits a solid object, the more damage it does.  In our case, we were using a solid wall that could not just flow out of the way, so our propelled bottle exploded an opening in the metal siding.

The experiment revealed that speed is key to how a propelled object impacts the material it hits. This is demonstrated in the following stills, taken using a Go Pro at 120 frames per second (these 3 images are literally 3 frames of video) :

wind damage bottle 1wind damage bottle 2wind damage bottle 3

Although the objects used were not propelled from a cyclonic vortex, we were still able to reproduce speeds of between 100 mph and 176 mph (equivalent to a EF4 tornado), and as you can see the bottle was going fast enough to become a slight blur to our Go Pro camera…that is until it collided with the metal siding.

Though the science used in this experiment does not match the exact science of a tornado vortex (it also doesn’t explain how a tornado plucks feathers off a chicken), it does help us understand how damage is caused during tornados, which makes determining the source of damage all the more easier.

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