I use the strong jet from the middle part of a handheld shower to rinse my hair and it’s always been really counterintuitive to me:
The jet can downright sting when it’s at just the right distance, but the closer I bring it to my head, the less I feel it, until it doesn’t feel like any pressure at all when it’s right up against my scalp.
I’d expect the energy to dissipate, and for the jet to get weaker with distance. Why is it the reverse?
In: 3
Turbulence
Water comes out in a laminar flow from the shower nozzles, but as it travels through air it faces resistance and the jet becomes turbulent.
Laminar flow is smooth to our skin and the turbulent flow feels rough because it’s more like a few micro drops hitting you, instead of just one.
To make it bigger and easier to see, open the faucet in your sink just enough so the water comes as smooth and clear as possible. A few inches down the water, it will look not as clear, much rougher – or turbulent – than right by the faucet. Now put your finger through that stream: when through the laminar (smooth) flow, you’ll barely feel it; when through the turbulent flow, you’ll feel it like a vibration.
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