# 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?

There’s one in every crowd.

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

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

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

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

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:

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?

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.

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.

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:

Bedford Brown. It is like mauve.

Have a happy Friday.