Why does rainwater pool into a shape of windshield wipers?

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I’m sitting in my car, it’s raining and wipers are off. However, I can clearly see how the droplets pool in a specific manner, reminiscent of wiper movements. Can someone explain the physics behind it?
Here’s how it looks like: https://ibb.co/C5M7YCL

In: Physics

4 Answers

Anonymous 0 Comments

the glass that is under the wiper’s coverage is cleaner/dirtier than the edges where the wipers dont cover. This causes the water droplets to behave differently due to the amount/lack of dirt or other chemicals to adhere to

Anonymous 0 Comments

Smooth glass and dirty glass grip water differently. The wipers keep the glass (relatively) clean.

A car that is washed frequently will see much less of this effect.

Anonymous 0 Comments

Your wipers could also have a water repellent that gets applied as you use them. This causes the water to bead up and run off your windshield. The pattern is where the wipers apply it to your windshield regularly.

Anonymous 0 Comments

Where there’s a bit of non-oily grime, the water can’t bead up like it normally would. Clean glass allows water to do its thing.

For eli12, it’s surface tension.

For eli14, The non-oily grime has polar molecules or ions that interact with the highly polar water that keep water from only pulling on itself, creating a surface that beads.

It’s nothing to do with polishing, btw.