Slashdot Mirror
Solving the Great Shower Curtain Mystery
parvati writes: "The New York Times is reporting that a UMass professor, Dr. David Schmidt, used computer modeling to figure out why shower curtains suck inward during showers. He designed an image of his mother-in-law's shower, filled it with 50,000 3D velocity/pressure sensors, and turned on the virtual water. 1.5 trillion calculations later, he found that drag on the falling water drops creates a mini-hurricance, producing a low-pressure 'eye' that attracts the shower curtain."
Really, I don't mean to flame, but just because something is old, dirty, used, etc. dosen't mean that it is not worth putting a little elbow grease into. The environment is turning into shit. It may be nice and shiny where you are, but there are places (like where that shower curtian would go) that absolutely suck. It all has to go somewhere.
I'm not saying keep everything! Of course, there are practicality reasons -- it may not be practical to clean the curtain if the chemicals to do so cost more than replacing it, or will potentially cause more environmental damage than just tossing the curtian.
Then there is the lack of education. You may not know how to clean the shower curtian. I can't tell you how many times I have found electronics (tv's, computers, a few SGI's from LockheedMartin, you know the standard faire...) that were in some simple state of disrepair. I changed the plug and coord on a 32" tele that I found by my dumpster in the alley; otherwise it was in supreme condition. It works excelent! I assume they left it there because they either didn't have the time to fix it, or they didn't know how. This was an $800 dollar tv in it's day. Unless someone is so rich to spend an hour (as if) trying to fix it, it just seems unlikely.
$800/hour! It makes me realize that fix-it guys can make it good if they market right.
That said, I am an american. But as a whole, I really hate america for their lazy-throw_away-buy_a_new_one-McCulture attitude, and unthoughtfulness. They then go and prosecute anyone who does not agree with their opinion. I may be misjudging you, but as a whole, america agrees with a hearty "Smack my fro!"
Plain and simple - Hampton Inn, who has the thinnest curtains I've ever seen, that suck inwards at the utterance of the words "I'm going to take a shower", needs to install some magnets on the bottom, or just spend an extra dollar per room for a real curtain.
Better yet, the plexiglass doors...that'd be one shower to make them bow in!
Slashdot should just get its own "partners" link already. Why the hell do we need to go through this dumb-ass two-step system where the main article posts some NYTimes registration-required link and someone else ferrets out a no-reg-required link?
Cut to the chase already, Slashdot. Beg, borrow or buy a damned registered partner account with the NYTimes and be done with it!
--
--
Don't like it? Respond with words, not karma.
It seems that somebody is already planning to do that.
-
Stop worrying about the risks of nuclear power and start worrying about the risks of not using nuclear power.
Holy crap! A waterfall down the center of the building would be really cool, since it'd have to be exposed to work... I'll have to work that into future houseplans. :)
My own research suggests that the likelyhood of the shower curtain being attracted to your skin is directly proportional to the amout of scum on it.
..........FULL STOP.
question 1. there's a lip on it that the last drop can't crest, hence, still in the can
question 2. you're ugly
question 3. you're a dork
see, I answered your questions and I don't even know you. Good luck finding anyone willing to shell out grant money for those.
cheese logs keep my wang warm at night.
Bernoulli principle - decreased pressure exerted by air in motion - the same physics that allows airplanes to fly
...
I've never found this believable, and thought a recent scientific american article addressed the problem well. As I understand it the traditional explanation goes like 'the top of the wind has more curvature and so the air has to travel further when the flow isn't turbulent so it has to be moving faster and so by Bernoulli's principle implies that the pressure above the wing is lower than the pressure below the wing so there is a net force upwards'.
Where are Newton's laws of motion in this picture? And how does it explain airplanes successfully flying upside down? A more plausible answer(to me anyway) involves the angle of attack the wing makes. Air is forced downwards and by conservation of momentum something must be forced upwards - the plane. The curvature of the wing is necessary to maintain non-turbulent flow without which there wouldn't be a regular stream of air flowing downwards. Increasing the angle of attack too much causes this to break down.
I find this explanation intuitive and more in accord with the rest of my knowledge of physics, but I'd love to hear objections
:wq
Tonight, my dear Pinky, we shall create a superweapon that creates hurricanes! First, we shall need to build the WORLD'S BIGGEST SHOWER STALL! ...
I'm trying to teach myself to set people on fire with my mind... Is it hot in here?
First a quick summary (apologies to those who read the article). Historically the billowing shower-curtain theorists have been divided into two camps:
- Those who appealed to the chimney effect - hot air rising within the shower causes cool air to come in from below. This hypothesis can be readily defeated by taking a cold shower and observing that the curtain billows nonetheless.
- Those who appealed to the Bernoulli principle - decreased pressure exerted by air in motion - the same physics that allows airplanes to fly and causes two sheets of paper to stick together when you blow between them (try it!). This hypothesis also seemed a bit shaky since (a) the air in a shower never seems to move that fast; and (b) there's a potential confusion of cause and effect going on here (for the shower curtain to billow, clearly something must be happening with the air pressure...).
Now comes David Schmidt to demonstrate that both of these camps are wrong (in this he and Cecil agree). His theory instead focuses on the deceleration of the water droplets by the air producing a cyclone effect within the shower. This theory is similar to, but distinct from, the ``entrainment'' theory that Cecil put forward so many years ago. And to me, significantly more believable.The same dynamics that causes hurricanes, right there in our very bathrooms! Score one for Schmidt and his finite element approach to a classic problem.
-Renard
Maybe you should read the article before posting things like this. Of course, you got modded up, so the same should probably go for the moderators.
What you describe is NOT the cause of the movement, as determined by Dr. Schmidt. He clearly states that the motion results from the water droplets giving up energy to the air as drag occurs. Effectively even the cold water is heating the air due not to temperature but because of its slowing velocity. (lots of drops=lots of surface area to volume=lots of drag)
The article justs states that (something magic happens, and then) you have a miniature hurricane. Probably this is due to temperature differentials in the system, in the same way that weather is created in the "real world."
It really isn't overkill. It's a much more subtle problem than your comment indicates.
Since I'm not married, I'm not certain, but would many of the readers here want even a mental image of their mother-in-law's shower, much less a super accurate computer picture?
I am !amused.
The pursuit of knowledge.
There is yet 3 stages of science.
Observation.
Discovery.
Technology.
Ask any geek, the more "sexy" stage of science is the last one, the stage where that we can lay our hands on it and turn into something usefully and productive. Yet the first 2 stages of science are seen as a "waste of time" or sometimes even "worthless". Hardly NOT so! You can have this sexy technology without the other two!
The guy in the above article did both 1 and 2 for us, it is our turn to make 3 happen. What could we use this for? Oh I don't know, say find a way to better predict when a hurricane is coming? Now that would be "sexy" technology that you would see on the 6:00 news.
That is not his job, he did 1 and 2 and did it very well if I might add, very detailed and very though.
The next guy that says "this guy has way to much time on his hand" really needs to think about it and really ask himself if he is in it for the "geek" or the "glory"
If the "glory" is what you are into that is fine, but please do give up respect to the guy in the above article that did all the "geek" for you.
"`Ford, you're turning into a penguin. Stop it.'" -THHGTTG
You're trying too hard here, why can't you both be right? Planes that fly upside down do not do so indefinately, and require a greater amount of thrust and angle of attack to overcome gravity and 'reverse lift' than an aircraft in normal flight. They also are incapable of maintaining a constant altitude during inverted flight, with few exceptions (trust me, I used to fly stunt planes, it's not as simple as it appears).
Basically, when inverted, the angle of attack is changed such that the 'reverse lift' (downward force generated by pressure differential) is minimized as much as possible, at the same time allowing some thrust to be converted to lift (by pointing the prop/jet output slightly down). This is basically the the 'kite' type of flight that you refer to.
Now, about those exceptions - aircraft capable of producing enough thrust to overcome gravity without the help of lift are often known as rockets, or in some cases military aircraft. Take a Mig27, with ~40,000lbs of thrust and wighing only ~30,000lbs, the wings are almost superflous, however they still remain, primarily as control surfaces, and efficiency aids (fuel goes fast when producing enough thrust to throw a 20 ton mass directly skyward).
I know it seems a tad illogical at first, but get a good hands-on book on flying, and try some of the experiments, you'll be amazed at what is proveable....
Think outside the... Hey, where'd the friggin' box go?
Sounds like something to help you avoid that whole Psycho shower scene...
Help save the critically endangered Blue Iguana
-Elentar
The wheel it turns, around and around, with an ancient rumbling sound.
This is just in time, since I'm currently staying with my mother-in-law while my house is being remodeled, and she has a particularly irritating shower curtain!
Hey, I've been critical of Slashdot's editorial policies in the past, but here is NEWS I CAN USE!!!
--
Sometimes it's best to just let stupid people be stupid.
What if this isn't true? I always assumed the shower curtain thing was heat conduction, and I was wrong.
Try this:
<ALTERNATE HYPOTHESIS>
The answering machine voice dorkification effect is caused by a neural association/feedback change. When you speak, your brain is not only hearing the sounds you make, but is also sending commands to your vocal apparatus instructing it to make those sounds. The correlation between hearing and speech center activity results in a difference in perception from just hearing alone.
</ALTERNATE HYPOTHESIS>
Weird you say? There's even a precedent for my idea. When you move your eyes, images sweep across them at hundreds of degrees per second - but the world doesn't look like it's moving to you. But if you look at a screen, hold your eyes still, and sweep images at those rates everything looks like it's moving. Why? Because when you move your eye, your brain takes a copy of the eye-motion commands and subtracts that motion from what the eye really sees, resulting in a perception that the world didn't move.
I admit, it's pretty far-fetched and I'm still inclined to believe the eustachian tube hypothesis, but the truth is we don't know unless someone's actually done the science to tell.
Research like this is great because it replaces supposition with real knowledge. Three cheers to this shower dude.
I stole this sig from someone cleverer than me.
A unified theory of physics.
Donate background CPU time to fight cancer.
1) Everyone ignores it
2) Everyone attacks it
3) Everyone claims it is obvious
* Blatantly plagiarized from some quantum physicist whose name I can't recall, probably Wheeler.
Milo
Now I can die happy knowing that shower curtains get sucked inward due to a small hurricane. I love science! We could be spending research time finding a way to get 500 miles to a gallon instead of worrying about showers.
Think of it as an indirect approach. For example, I was reading somewhere (cannot recall the source, but it was some magazine) about a scientist who decided to figure out why it was that coffee spills always dried with a dark ring around the outside. A whole lot of research later, science now knows a lot more about how molecules interact in fluids, which has led to practical applications such as (among many others that I cannot remember) fast-drying paint.
Many people make the same argument you're making about fields like pure mathematics -- the research doesn't always have any immediate practical value. But the knowledge often makes itself valuable in everyday life in unanticipated ways. How do you really know if a particular scientific "discovery" is useful unless you know what that discovery is in advance?
It's a disturbing trend nowadays that believes research time should only be spent on immediately practical applications. The pursuit of pure knowledge, or even simple curiousity, is increasingly pushed to the side. Yes, research is time-consuming and often expensive, but to solely measure the value of attaining knowledge based on its immediately foreseeable applications is (IMO) somewhat short-sighted.
Now I admit, I have no idea how knowing that a shower creates a small huricane will become personally useful to me. But that does not mean that some aspect of this will not become useful in the future.
I can spell. I just can't type.
Here.
Second, I think it's pretty obvious - this guy is definitely geek material. I mean, come on - crunching a 1.5 trillion calculation program over the span of two weeks on your free time? How many of us would love to have an excuse to do something like that?
Honestly, I wouldn't be surprised if he reads Slashdot :)
-Karl /dos]# file msdos.sys
-------------
[root@kgutwin
[root@kgutwin
msdos.sys: fsav (linux) virus (17518-87)
Fallingwater
Built in the '50s. Widely regarded as one of the most reconized private homes in America. (Now a museum, of course, but originally a residence.)
Nope, no sig
So if a butterfly flaps it's wings and causes a tornado on the other side of the planet -- what do millions of little huricanes in our showers every day do?
But the knowledge often makes itself valuable in everyday life in unanticipated ways. How do you really know if a particular scientific "discovery" is useful unless you know what that discovery is in advance?
You make a very valid point. One thing that has always burned me up, from my 1-12 grade years was when some mindless mundane would ask "Is this going to be on the test?" and if the answer was no they'd veg out and not learn what was to come.
For example, in and of itself it does no good for the ordinary person wo understand additive/subtractive properties of color when it comes to light/pigments however if you do know a little about them, it can help you to adjust the tint on your TV or adjust the color balance on your computer.
Trying to figure out which genetic traits were dominant/recessive in pea plants may have seemed like wasted research at the time, however that research was the foundation for later research that may (and probably will) lead to cures for diseases ranging from down's syndrom to cancer.
To quote the game company Midway, "There is no knowledge that is not power".
-You can cry, but you'll still die. There'll be no tears in the end.
The last dribbles of softdrink never come out of the can because of a couple factors. One, the surface tension of the droplets tends to make it "stick" to the can surface. Two, the inside of the top of the can is not perfectly smooth, and the opening in the can is relatively small. As a result, it's easy for a drop to get "stuck" in a nook or cranny on the can.
Driver's liscence photos always turn out bat because the DMV cares not a whit about how you look, so they don't bother with the higher-end cameras or even decent lighting that professional photographers use. Also, the photo is generally taken shortly after the driving exam, which tends to stress a person, effecting their appearence. Finally, few people bother to wear a nice shirt or whatever to make themselves look nicer in the photo.
People generally sound like dorks on answering machines because the sound quality on playback is usually poor, and strips most enotional nuances from speech. Thus, the recording sounds flat and "dorky". In addition, people are generally not used to giving monologues. When I talk, someone next to me usually gives a response, even if it's just "Shut up, Ethan". It's disconcerting to be prepared to speak with a person, and suddenly have to give all the information you intended to provide without any of the feedback you would have in a normal conversation. If you're calling to discuss, say, dinner plans, the other person you're calling can't ask for any clarifications (where are we eating? Which road should I take? Is it a formal dinner?) You need to provide all that information at once, and the added strain and performance anxiety leads to the normal verbal respones to stress. These include stammering, "null data" sounds such as "uh", "um", and mumbling. All of these sound "dorky". Of course, one could simply say "I'll call back later," but circumstances may not permit that, or you may simply feel pressured to provide the data to the machine then and there.
Of course, it is entirely possible that the reason you in particular sound dorky on answering machines, Nathdot, is that you are in fact a dork. I have not data to support that conclusion one way or the other, but it must be considered. After all, the simplest explanation is usually the correct one, as Occam's Razor asserts.
As for your plans to model and study these questions on supercomputers, well, more power to you! One problem, however: since you are studying absolutes (soda dribbles NEVER come out, liscense photos ALWAYS look bad, and you ALWAYS sound like a dork...on answering machines), how will you model each and every existing soda can, DMV camera, and answering machine? It's not enough even to model the different makes of these items, as each can, camera, or answering machine is at least slightly different from every other one, due to quirks in the manufacturing process. Even if you found a factor in one soda can using your supercomputer that contributed to "stuck soda", how would you prove all other soda cans have the same problem?
I'm the stranger...posting to
Yeah, in a perfect world of one-to-one dollar translation, there might be "better" things to spend it on, but, eh, it was cool, and he did it.
Good for him.
"Enough of this wretched, whining monkey life." -- Marcus Aurelius, _Meditations_, Book 9, 37
Some of my own proposed projects:
* Why the last dribbles of softdrink never make it out of the can
* Why drivers lisense photos always turn out bad
* Why I always sound like a dork on answering machines
I plan to model each one of these confounding human mysteries on a supercomputer using not 1, not 2, but 3 trillion!!! calculations...
Now!... Gimme that sweet sweet grant money!
:)