3 ms·

Wake can mean two things. I think you're confusing disturbance of the water that it passed through with travelling waves that appear as ripples on the water sur

Wake can mean two things. I think you're confusing disturbance of the water that it passed through with travelling waves that appear as ripples on the water surface in the case of boats. Submarines don't generate the latter type of wake. Of course they do consume some energy. They're not perpetual motion machines. That some energy goes into the former type of wake. The surface of the water allows a unique mode of energy transfer (surface waves) which doesn't exist without a surface. Underwater, energy can still be transmitted by sound, but that's not the same mechanism as surface waves. I'm skeptical that picture is a photo since it doesn't have blueing and darkening with distance. Maybe it's been doctored or is a small scale or something unnatural.

dingaling 5y ago
> Submarines don't generate the latter type of wake They do, and it's detectable through the bioluminescence it generates
- exporectomy 5y ago
  That's the former type. Maybe my sentence was too messy to clearly distinguish them. Ships generate a V-shaped surface wave and (deep enough) submarines don't.
thaumasiotes 5y ago
> Wake can mean two things. I think you're confusing disturbance of the water that it passed through with travelling waves that appear as ripples on the water surface in the case of boats. In what sense are these different things? How could you have one without the other?
- exporectomy 5y ago
  They're distinctly different physical phenomena. Surface waves are like spring-mass systems where gravity acts as the spring (hence they're also called gravity waves https://en.wikipedia.org/wiki/Gravity_wave https://en.wikipedia.org/wiki/Gravity_wave). They can't exist in a homogenous medium, like underwater approximately is. Since they're travelling waves, they carry energy when they travel away from the boat, so it's a source of energy loss.

dingaling 5y ago

> Submarines don't generate the latter type of wake They do, and it's detectable through the bioluminescence it generates

exporectomy 5y ago
That's the former type. Maybe my sentence was too messy to clearly distinguish them. Ships generate a V-shaped surface wave and (deep enough) submarines don't.

thaumasiotes 5y ago

> Wake can mean two things. I think you're confusing disturbance of the water that it passed through with travelling waves that appear as ripples on the water surface in the case of boats. In what sense are these different things? How could you have one without the other?

exporectomy 5y ago
They're distinctly different physical phenomena. Surface waves are like spring-mass systems where gravity acts as the spring (hence they're also called gravity waves https://en.wikipedia.org/wiki/Gravity_wave https://en.wikipedia.org/wiki/Gravity_wave). They can't exist in a homogenous medium, like underwater approximately is. Since they're travelling waves, they carry energy when they travel away from the boat, so it's a source of energy loss.