Talk:Shower-curtain effect

message: I recall my freshman's physics textbook that mentioned this very effect, and as I remember it was explained by Bernoulli's principle. Essentially, the windflow caused by the water creates an air-pressure differential between the inner wall of the curtain and the outer wall.. similar to the same effect that keeps an airplane in the air. Anyone care to weigh in? SaulPerdomo 03:28, 5 September 2006 (UTC)
thread_title:  Bernoulli's principle? 

message: * fyi: temperature difference = buoyancy effect = chimney effect. *
I've observed that cold showers do make a difference to the shower-curtain effect.  In my shower the curtain moves out if the shower is cold.  I think the buoyancy theory is the most correct anwer to the shower-curtain effect.  I don't disagree with the other work that has been done, but I think the chimney effect predominates over the vortex/Bernoulli/Coanda effects.  I have several observations to back up my claim and will just include a recent letter which spells things out mostly.
***
To: cecil@chicagoreader.com 
Sent: Friday, October 06, 2006 1:34 PM
Subject: shower curtain effect
Dear Sir,
It has been several years since I read the article about the shower curtain effect.  During the intervening time, I have observed my shower curtain under various conditions and I think there is more to add to this discussion.  
I am sure that Prof. Schmidt's work is valid, but I don't think that it has solved the problem "decisively."  I am sure that the buoyancy effect (temperature differential) is also a valid effect contributing to the overall shower curtain effect.
  
Moreover, I feel sure that the buoyancy effect predominates over the vortex/Coanda effects.  I copy below a letter that I wrote to an atmospheric scientist to see if I can get some hard data to back up this assertion.  There is no reply yet, but it's just been one day.  This letter will convey my thoughts well enough, and I'm wondering if you are still interested in this topic, the shower curtain effect.  If so, I will let you know what I can find out from my inquiry.
Ultimately I hope to contribute to updating the Wikipedia regarding the shower curtain effect, and maybe even get Scientific American to update the public also.
***copy of inquiry re: magnitude of effect-
...I don't know if you've ever heard of the "shower curtain effect," but you can look it up on the web easily (yes, real shower curtains; not the optical coherence tomography).
Anyway, I disagree strongly with the currently accepted wisdom on this effect and was going to try and edit the wikipedia.  I can see that my position has been raised before but discounted.  I have several points to resurrect the "buoyancy" argument, but would like to get some hard data to bolster my points.
***
So, my question is about the pressure differential caused by temperature differences.  I'm thinking that 1 torr might be equivalent to a difference of something in the range of 1 to 5 degrees  (C or F).  Do you have any sense of an answer for this or might you be able to pinpoint a resource and get a quote or at least point me to where I can look something up?
***
A fluid dynamics professor seems to have had the last word on this matter (Scientific American, Oct.2001) based on some computer simulation, but I think his explanation refers to an effect that is one or more orders of magnitude less than the temperature/buoyancy effects.  I also think any vortex, Bernoulli, or Coanda effects would be disrupted by the presence of a moving person and/or would only operate at very small distances.  I'm hoping that you, as someone more in tune with large scale fluid dynamics, might be able to help me with this buoyancy vs. vortex question.
Thanks,
Sam...
***end copy of....
AND, not only do I feel the buoyancy effect is largely dominant, but I also have observations to point out the assertion that temperature makes no difference to the "inflow" of the shower curtain is wrong.  With a cold shower, the shower curtain bulges out and away from the water.  I think the focus needs to be on real-life conditions, so the bathroom door should be closed (affecting overall airflow dynamics), and even the presence or absence of people (in or out) as observers or a showeree needs to be considered.
I don't think Prof. Schmidt's simulation included temperature effects; but even if so, the simulation represented 30 seconds -not enough time to see temperature effects.  While I appreciate his detailed and exacting contribution to the understanding of the shower curtain effect, I think that looking at the results of cold vs. hot showers will lead to a much fuller understanding of the real-life shower curtain effect.
I have noticed that a space heater in the bathroom, running during a shower, will completely solve the problem of an inflowing shower curtain (not responsible for injury or property damage).  The hot air added also has the benefit of absorbing all of the humidity from the shower, preventing steamy mirrors, etc.  I use an exhaust fan and/or window to keep the room from gettng too hot.
Thanks for your time with this,
Sincerely,
Sam....
Samwikster 15:05, 9 October 2006 (UTC)
thread_title:  Cold Showers:10/06 

message: The wikipedia definition of "shower-curtain effect" includes the clause, 'regardless of the temperature of the water.'  If we're interested in real-life clingly, billowing shower curtains, then temperature should not be defined out of the equation.  Based on published articles about the shower-curtain effect, I can see how this assumption came about; but a more careful reading of the published literature will reveal little, if any, controlled observations on the temperature effects.  Also, the published articles do admit that temperature contributes to the effects.   
I copy below a letter to Scientific American regarding this problem.  If there is any published data or controlled observations on this temperature problem, please contact me with the information.
***
To: experts@sciam.com 
Sent: Monday, October 09, 2006 12:24 PM
Subject: Shower-Curtain Effect Testing?
Dear Sirs,
Regarding the 5 year old article on the Shower Curtain Effect, I can see this topic generated a bit of heated input in the past.  While it was nice to see a detailed explanation and a new twist for part of the discussion, this article seems to have become the final word regarding the shower curtain effect.  Until the buoyancy effects can be quantified to a level on par with the cited vortex effects, I don't think there should be any fiinalized theory regarding the shower-curtain effect.
In the article from FluentNEWS, Prof. Schmidt acknowledges that it is "certainly a combination of... longstanding theories" that cause the shower curtain effect.  His results are stated as to only "suggest that the vortex motion is the dominant factor that drives this phenomenon."
Overall, the resolution of these shower curtain theories (we should all be using the word hypothesis about this!) will only come after resolving the cold shower paradox.  Throughout the readings on this topic, I find statements about how temperature doesn't matter.  If as much care were put into testing this assertion as Professor Schmidt put into his efforts, then I feel sure temperature would be seen as a dominant factor in the shower-curtain effect.  It also seems unlikely, under real-life conditions (a person in the shower, moving around), that a Schmidt vortex could be stable and persist.  I would think a person turning and bending would produce vortices roughly equivalent to the Schmidt vortex.  Also in real-life conditions, the water may only travel a few inches before then just running down the body.
Torque on the shower curtain is what we are really interested in here, I think.  As measured just by deflection of the bottom of the curtain, a cold shower will first pull my shower curtain in about a quarter of an inch; but [make sure the bathroom door is closed] after a minute or two, the curtain is deflected outward by several inches!  I see this as a slight inward force initially, probably a Schmidt vortex, but one to be soon overpowered by a force several orders of magnitude greater in the outward direction -a buoyancy/chimney effect.  And hot water causes the same large deflection, but inward.
Now with room temperature water only, one should see the true effects of vortices, Bernoulli, and Coanda effects.  If your arm swings close by the shower curtain, a vortex will pull the curtain in slightly and if a tiny bit happens to touch a drop of water on your skin then Coanda effects take over and lead the rest of the shower curtain to begain wrapping around.  Of course, then you jump and that creates more vortices, leading to much wasted time and water.
Ultimately, we'll need a rough estimate of the negative pressures generated by these non-temperature dependant effects; and we'll need to see how these pressures work at distances operating in a typical shower area -what torque they can produce on a shower curtain at various distances (maybe 1/4 to about 48 inches) from the area of low pressure.  When these can be compared with the pressures (torque) created by temperature differentials, then we will have a more complete answer-and be able to see better solutions- to the billowing problem.
The solution of magnets or weights on the bottomof the shower curtain would only seem to make the problem move up so the middle would push in.  Then the curtain is closer to the water and the vortices might take over.  I've posted a different solution on the Wikipedia discussion page for "shower-curtain effect," based on buoyancy consideration, which works much better than magnets for my shower curtain.
  
I can see each shower and bathroom probably have a unique combination of design geometry and materials that will generate a unique combination of the different forces acting to create the shower-curtain effect  but I think that when everything is examined evenly, the buoyancy effect will be seen to predominate in any real-life shower.
Sincerely,
Sam...
Samwikster 18:56, 9 October 2006 (UTC)
thread_title:  Testing Shower-Curtain Effect 

message: Substituted at 06:04, 30 April 2016 (UTC)
thread_title: Assessment comment

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