The Aerodynamics of Convex v. Concave (Pictures)

Hi.

So, I was taking the trash out yesterday evening, and I noticed that when I violently swung open the trash bin lid, it was a breeze. (See what I did there?) But when I went to close it, I was met with some difficulty. It got me thinking about the science behind it, and so I thought I’d dedicate a post to my findings. But don’t worry; this will not be simply textbook-speak. Of course I am going to include diagrams. CRUDE diagrams, which I drew myself, on an app called Drawing Desk. Who doesn’t love amateur drawing hour?
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There’s one in every crowd.

Okay, kids, today’s lesson is essentially going to be about circles.

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Something that is concave has an outline or surface that curves inward like the interior of a circle:

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Conversely, something that is convex has an outline or surface that curves outward like the exterior of a circle:

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Now that we know the difference, a concave shape is less aerodynamic than a convex shape, because:

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The curve acts as resistance and the wind cannot go in the direction it naturally wants to go in.

On the other hand, a convex shape is more aerodynamic because:

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The curve in this case follows the direction of the wind and thereby allows it to ‘roll’ right off the surface and continue on.

Pretty fascinating, huh?

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Calm down.

The circumstances are similar if you try to swim along or against the current. In that case, though, the term is hydrodynamic, because water. The prefix aero- refers to air/wind, while the prefix hydro- refers to water. Everything comes back to language.

It’s highly likely that most of you already knew all of this. But maybe there is a microscopic percentage of readers who are in third grade, in which case you are welcome. When ABC Mouse decides to feature this life-altering lesson of mine, I will elect to receive a stipend via PayPal.

If you feel your time was wasted by reading this, don’t leave just yet. Please enjoy this picture of a cat who doesn’t know what is going on.

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Now you may leave.

Please feel free to tune in next week when we will discuss the delicious crustacean that is the soft-shelled crab.

(Not really.)

Epilogue

I want to end this post by saying that I’m in the process of moving. Though I try to post every day or every other, that may not be feasible until the end of next week, when I should be settled in.

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Look at all that crap. That’s not even the bulk of it. The good news, though, is that I am painting my new bedroom later on today. I wonder what color, you may be thinking. To that, I say this:

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Bedford Brown. It is like mauve.

Have a happy Friday.

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