4 ms·

The news is that someone worked out the maths behind it and wrote it down - then proved they were right. It's a bit like the fact that everyone knows the showe

The news is that someone worked out the maths behind it and wrote it down - then proved they were right. It's a bit like the fact that everyone knows the shower curtain will billow towards them in the shower but no one has managed to prove why that happens.

davidhyde 7y ago
Great answer, cheers
aaron695 7y ago
> shower curtain will billow towards them in the shower but no one has managed to prove why that happens. This is an embarrassment to science. It's why people don't trust scientists. This is a serious issue, how can we seriously not decide on the solution to such a simple problem involving fluid dynamics? Is science really this broken? https://en.wikipedia.org/wiki/Shower-curtain_effect https://en.wikipedia.org/wiki/Shower-curtain_effect
phkahler 7y ago
Because the hot air inside rises and cooler air pushes inward. It's called convection, and I don't thing anyone needs to run a simulation and publish a paper solving the "shower curtain problem" just because it hasn't been "done" before.
- Simon_says 7y ago
  If the water is air-temperature or colder, then curtain does or doesn't blow inward? Care to make make a prediction based on your theory?
- Nadya 7y ago
  Straight from the first paragraph of the Hypotheses section, emphasis mine. >Also called Chimney effect or Stack effect, observes that warm air (from the hot shower) rises out over the shower curtain as cooler air (near the floor) pushes in under the curtain to replace the rising air. By pushing the curtain in towards the shower, the (short range) vortex and Coandă effects become more significant. However, the shower-curtain effect persists when cold water is used, implying that this cannot be the only mechanism at work. Scientists investigate and prove things that are "common sense" things all the time because the "common sense" answer turns out to be wrong.
- dekhn 7y ago
  scientists have been arguing about the exact physical forces in this problem for a long time (similarly true for airplane wings). We like to actually confirm our theories with experimental data, and often times, these sorts of papers help the field in unexpected ways in the long term.
- thaumasiotes 7y ago
  It has been done before. See the physics winner for 2001: https://improbable.com/ig/ig-pastwinners.html https://improbable.com/ig/ig-pastwinners.html
  - lexicality 7y ago
    I like that it took him two weeks of compute time and it's only a "partial solution"
    - thaumasiotes 7y ago
      That's fluid dynamics for you. :-/
sohkamyung 7y ago
Indeed. There are a few hypotheses about it [1] [1] https://en.wikipedia.org/wiki/Shower-curtain_effect https://en.wikipedia.org/wiki/Shower-curtain_effect
- vanderZwan 7y ago
  I can definitely imagine this being really hard to work out in an equation, but I'm somewhat surprised that this implies that it has been difficult to come up with experiments that would give data that might help figure this out. Surely we have ways of measuring air vortices and pressure that would clarify a lot of what is happening to the air flow?
  - jallasprit 7y ago
    Funny coincidence! I thought about this when I showered this morning. The water probably sucks air down the drain with it, causing slightly negative pressure causing the curtain to bellow inwards.
    - DataGata 7y ago
      Down the drain? I might buy the water sucking down air, but down the drain?
    - jtbayly 7y ago
      Isn't the point of traps largely to prevent air from traveling either direction through the drain?
  - lexicality 7y ago
    I'd love to be on the grants committee when someone requests funding to set up a shower in their lab. The thing that makes this more interesting is that if you have a large shower (eg a wheelchair wetroom) then the shower curtain behaves differently depending on where you are inside it. Try walking up and down your bathtub next time you have a shower.
    - deleted 7y ago
bawana 7y ago
The shower thing is explained by the coanda (Bernoulli) effect.
- nikanj 7y ago
  "The problem of identifying the cause of this effect has been featured in Scientific American magazine, with several theories given to explain the phenomenon but no definite conclusion." According to a quick googling, not really.
- maaaats 7y ago
  According to you. Another answer says it's convection. So not so intuitive after all ;)
- thaumasiotes 7y ago
  > the coanda (Bernoulli) effect Those are two different effects.

davidhyde 7y ago

Great answer, cheers

aaron695 7y ago

> shower curtain will billow towards them in the shower but no one has managed to prove why that happens. This is an embarrassment to science. It's why people don't trust scientists. This is a serious issue, how can we seriously not decide on the solution to such a simple problem involving fluid dynamics? Is science really this broken? https://en.wikipedia.org/wiki/Shower-curtain_effect https://en.wikipedia.org/wiki/Shower-curtain_effect

phkahler 7y ago

Because the hot air inside rises and cooler air pushes inward. It's called convection, and I don't thing anyone needs to run a simulation and publish a paper solving the "shower curtain problem" just because it hasn't been "done" before.

Simon_says 7y ago
If the water is air-temperature or colder, then curtain does or doesn't blow inward? Care to make make a prediction based on your theory?
Nadya 7y ago
Straight from the first paragraph of the Hypotheses section, emphasis mine. >Also called Chimney effect or Stack effect, observes that warm air (from the hot shower) rises out over the shower curtain as cooler air (near the floor) pushes in under the curtain to replace the rising air. By pushing the curtain in towards the shower, the (short range) vortex and Coandă effects become more significant. However, the shower-curtain effect persists when cold water is used, implying that this cannot be the only mechanism at work. Scientists investigate and prove things that are "common sense" things all the time because the "common sense" answer turns out to be wrong.
dekhn 7y ago
scientists have been arguing about the exact physical forces in this problem for a long time (similarly true for airplane wings). We like to actually confirm our theories with experimental data, and often times, these sorts of papers help the field in unexpected ways in the long term.
thaumasiotes 7y ago
It has been done before. See the physics winner for 2001: https://improbable.com/ig/ig-pastwinners.html https://improbable.com/ig/ig-pastwinners.html
- lexicality 7y ago
  I like that it took him two weeks of compute time and it's only a "partial solution"
  - thaumasiotes 7y ago
    That's fluid dynamics for you. :-/

sohkamyung 7y ago

Indeed. There are a few hypotheses about it [1] [1] https://en.wikipedia.org/wiki/Shower-curtain_effect https://en.wikipedia.org/wiki/Shower-curtain_effect

vanderZwan 7y ago
I can definitely imagine this being really hard to work out in an equation, but I'm somewhat surprised that this implies that it has been difficult to come up with experiments that would give data that might help figure this out. Surely we have ways of measuring air vortices and pressure that would clarify a lot of what is happening to the air flow?
- jallasprit 7y ago
  Funny coincidence! I thought about this when I showered this morning. The water probably sucks air down the drain with it, causing slightly negative pressure causing the curtain to bellow inwards.
  - DataGata 7y ago
    Down the drain? I might buy the water sucking down air, but down the drain?
  - jtbayly 7y ago
    Isn't the point of traps largely to prevent air from traveling either direction through the drain?
- lexicality 7y ago
  I'd love to be on the grants committee when someone requests funding to set up a shower in their lab. The thing that makes this more interesting is that if you have a large shower (eg a wheelchair wetroom) then the shower curtain behaves differently depending on where you are inside it. Try walking up and down your bathtub next time you have a shower.
  - deleted 7y ago

bawana 7y ago

The shower thing is explained by the coanda (Bernoulli) effect.

nikanj 7y ago
"The problem of identifying the cause of this effect has been featured in Scientific American magazine, with several theories given to explain the phenomenon but no definite conclusion." According to a quick googling, not really.
maaaats 7y ago
According to you. Another answer says it's convection. So not so intuitive after all ;)
thaumasiotes 7y ago
> the coanda (Bernoulli) effect Those are two different effects.