3 ms·

It reminds me of PNP & NPN transistors. Could these liquid "defects" have applications too? Ever since childhood I've wondered why the water behind a rowboat s

It reminds me of PNP & NPN transistors. Could these liquid "defects" have applications too? Ever since childhood I've wondered why the water behind a rowboat stays flat for so long. You'd think the surrounding water would flow in and make it as wavy as everything else. Then a few years ago I was on Thera and saw the same thing with the cruise ships coming in. Their flat glassy trails would last for hours. Why does it take so long for them to vanish? It is a liquid transition that is weirdly persistent. Does anyone have an answer? If not, maybe this can be someone's wobbling plate.

Enginerrrd 5y ago
If I recall correctly, I think this is usually explained as a thermocline effect where as deeper water gets churned up and mixed in the wake, it is a different temperature than the surrounding water outside the wake. This water has ever-so-slightly different fluid characteristics and so it presents a bit of a barrier to the usual diffusion and mixing you might expect. There's also the potential for a very thin layer of some type of hydrophobic substance (like an oil) to be left behind that can dramatically reduce waves in that area. There's youtube videos around for that effect.
- hinkley 5y ago
  Probably a different amount of dissolved gasses as well.
hinkley 5y ago
WAG: does it have anything to do with dissolved gases slightly changing the physics of the water, making it a case of the waves seeing it as a transition between materials.
hyperpallium2 5y ago
IDK but one factor is most of the water filling the gap would come from underneath (it's at higher pressure), moving up to the surface. Its momentum carries it slightly too high, so it flows outward, then down and inward again, forming a vortex on either side. The surface looks smooth and the twin vortices woukd tend to persist.
ransom1538 5y ago
Start simple. Take a bucket of legos and run your finger through it. It will do the exact same thing - but much slower. When you embark on these super complex differential equations (people barley understand) - just go backwards.

Enginerrrd 5y ago

If I recall correctly, I think this is usually explained as a thermocline effect where as deeper water gets churned up and mixed in the wake, it is a different temperature than the surrounding water outside the wake. This water has ever-so-slightly different fluid characteristics and so it presents a bit of a barrier to the usual diffusion and mixing you might expect. There's also the potential for a very thin layer of some type of hydrophobic substance (like an oil) to be left behind that can dramatically reduce waves in that area. There's youtube videos around for that effect.

hinkley 5y ago
Probably a different amount of dissolved gasses as well.

hinkley 5y ago

WAG: does it have anything to do with dissolved gases slightly changing the physics of the water, making it a case of the waves seeing it as a transition between materials.

hyperpallium2 5y ago

IDK but one factor is most of the water filling the gap would come from underneath (it's at higher pressure), moving up to the surface. Its momentum carries it slightly too high, so it flows outward, then down and inward again, forming a vortex on either side. The surface looks smooth and the twin vortices woukd tend to persist.

ransom1538 5y ago

Start simple. Take a bucket of legos and run your finger through it. It will do the exact same thing - but much slower. When you embark on these super complex differential equations (people barley understand) - just go backwards.