question: What scientific phenomena is responsible for my cold, wet, shower curtain always trying to float towards my naked body while I'm taking a shower?
comment: Shower water heats up the air, and the hotter air escapes the shower cubicle via the gap above the curtain. Colder air from the rest of the room tries to get in to replace it, pushing the curtain inward towards you. Work-around: Don't pull the curtain sideways all the way. Leave a gap between the curtain and the wall, 4-6 inches, at the far end. Cold air will get in through there.
passages: 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.
  
  See also Cooling tower.
  
  Section::::Hypotheses.:Bernoulli effect hypothesis.
   Section::::Hypotheses.:Horizontal vortex hypothesis.
  
  A computer simulation of a typical bathroom found that none of the above theories pan out in their analysis, but instead found that the spray from the shower-head drives a horizontal vortex. This vortex has a low-pressure zone in the centre, which sucks the curtain.
   David Schmidt of University of Massachusetts was awarded the 2001 Ig Nobel Prize in Physics for his partial solution to the question of why shower curtains billow inwards. He used a computational fluid dynamics code to achieve the results. Professor Schmidt is adamant that this was done "for fun" in his own free time without the use of grants.
  
  Section::::Hypotheses.:The Coandă effect.
  
  The Coandă effect, also known as "boundary layer attachment", is the tendency of a moving fluid to adhere to an adjacent wall.
  
  Section::::Hypotheses.:Condensation.
   Colder dense air outside and hot less dense air inside causes higher air pressure on the outside to force the shower curtain inwards to equalise the air pressure, this can be observed simply when the bathroom door is open allowing cold air into the bathroom.
  
  Section::::Solutions.
  
  Many shower curtains come with features to reduce the shower-curtain effect. They may have adhesive suction cups on the bottom edges of the curtain, which are then pushed onto the sides of the shower when in use. Others may have magnets at the bottom, though these are not effective on acrylic or fiberglass tubs.
   It's possible to use a telescopic shower curtain rod to block the curtain on its lower part and to prevent it from sucking inside.
  
  Hanging the curtain rod higher or lower, or especially further away from the shower head, can reduce the effect. A (convex) curved shower rod can also be used to hold the curtain against the inside wall of a tub.
   A weight can be attached to a long string and the string attached to the curtain rod in the middle of the curtain (on the inside). Hanging the weight low against the curtain just above the rim of the shower pan or tub makes it an effective billowing deterrent without allowing the weight to hit the pan or tub and damage it.
  
  There are a few alternative solutions that either attach to the shower curtain directly, attach to the shower rod or attach to the wall.
  
  Section::::External links.
  
  BULLET::::- Scientific American: Why does the shower curtain move toward the water?
   A hot shower will produce steam that condenses on the shower side of the curtain; lowering the pressure there. In a steady state the steam will be replaced by new steam delivered by the shower but in reality the water temperature will fluctuate and lead to times when the net steam production is negative.
  
  Section::::Hypotheses.:Air pressure.
   Shower-curtain effect
  
  The shower-curtain effect in physics describes the phenomenon of how a shower curtain gets blown inward with a running shower. 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.
  
  The shower-curtain effect may also be used to describe the observation how nearby phase front distortions of an optical wave are more severe than remote distortions of the same amplitude.
  
  Section::::Hypotheses.
  
  Section::::Hypotheses.:Buoyancy hypothesis.
   The most popular explanation given for the shower-curtain effect is Bernoulli's principle. Bernoulli's principle states that an increase in velocity results in a decrease in pressure. This theory presumes that the water flowing out of a shower head causes the air through which the water moves to start flowing in the same direction as the water. This movement would be parallel to the plane of the shower curtain. If air is moving across the inside surface of the shower curtain, Bernoulli's principle says the air pressure there will drop. This would result in a pressure differential between the inside and outside, causing the curtain to move inward. It would be strongest when the gap between the bather and the curtain is smallest - resulting in the curtain attaching to the bather.
   BULLET::::- Why does the shower curtain blow up and in instead of down and out?
  
  BULLET::::- Video demonstration of how this phenomenon could be solved.
  
  BULLET::::- The Straight Dope: Why does the shower curtain blow in despite the water pushing it out (revisited)?
  
  BULLET::::- 2001 Ig Nobel Prize Winners
  
  BULLET::::- Fluent NEWS: Shower Curtain Grabs Scientist – But He Lives to Tell Why
  
  BULLET::::- Arggh, Why Does the Shower Curtain Attack Me? by Joe Palca. "All Things Considered", National Public Radio. November 4, 2006. (audio)
   It is also important to note that each fluid has its own minimum flow rate. The minimum flow rate is the smallest amount of dye at a given moment to keep the curtain flowing continuously. The minimum flow rate is directly proportional to the surface tension while viscosity is inversely proportional.
   Section::::Structure and design.:Shower and bathtub curtains.
  
  Curtains can be used in shower or bathtub enclosures with two main purposes: to provide privacy and to prevent water from flooding or spraying outside the shower or bathtub area. Shower and bathtub curtains usually surround the bath inside the tub or shower area and are held up with railings or curtain rods high on the wall or ceiling. To accommodate the different types of bathtub shapes, railings can come in different sizes and are flexible in their design. 
   Shower or bathtub curtains are more commonly installed because of their very low cost and ease of installation, requiring only a rod, which may be removable, that spans between the end walls of the open side of the bathtub, and rings or hooks for attaching the curtain. The waterproof curtain or liner is placed inside the bathtub during and after shower use to contain water spray and splashes within the bathtub for proper drainage while drying. However, they are not highly effective: if the curtain is not very carefully arranged, then water escapes and puddles on the floor, near the wall at the end of the shower curtain, particularly at the end where the shower head was located.
   An olio requires a sturdy roll tube to prevent sagging. The larger the tube diameter, the more readily it will descend when the ropes are loosened.
  
  Section::::Types.:Traveler.
   On the right image, the effect occurs along the curved wall as a "wall jet". The image here on the right represents a "two dimensional wall jet" between two parallel plane walls, where the "obstacle" is a quarter cylindrical portion following the flat horizontal rectangular orifice, so that no fluid at all is entrained from the surroundings along the wall, but only on the opposite side in turbulent mixing with ambient air.
   Uncoated fabrics provide the next level of heat insulation and light absorption. Uncoated fabrics constitute the vast majority of fabrics used in curtains, and are composed of a tightly woven fabric, most typically a cotton/polyester blend, which is mostly opaque when viewed in ambient light. Uncoated fabrics provide a reasonable level of heat insulation due to the tight weave of the fabric. However, the fabric itself is typically not thick enough to completely absorb strong light sources. As a result, when curtains made from uncoated fabrics are closed in an attempt to block out direct sunlight, light will still be visible through the curtain.
   Curtain coating is one of the technologies used in the converting industry to modify the properties of substrates.
  
  Section::::Edging.
  
  To be certain the flow of the liquid is disrupted, an edging along both sides of the slit is required. This is to prohibit the surface tension from causing the coating to taper in; sometimes edging alone is not enough and a surfactant must be added to lower the surface tension.
  
  Section::::Flow rate.
   Section::::Description.
   BULLET::::- to reduce liquid or debris floating on the surface from spreading
  
  BULLET::::- to prevent salt intrusion
  
  BULLET::::- to control the movements of fish
  
  BULLET::::- for decoration and airing in aquariums
   Würsig and several colleagues developed and tested a bubble curtain system to reduce underwater industrial noises, and this technique has more recently received much engineering and environmental attention.
  
  Section::::Major Publications.
   Section::::Design concerns.:Deflection.
   A variation on the Austrian is the "waterfall" curtain: in this version, instead of horizontal festoons, the curtain has vertical pleats like a traditional theater curtain, but it still gathers from the bottom in a number of swags. The waterfall has a pipe batten along the bottom edge to ensure the lines rise evenly.
  
  Section::::Types.:Brail.
   Gravity currents are frequently encountered in the built environment in the form of doorway flows. These occur when a door (or window) separates two rooms of different temperature and air exchanges are allowed to occur. This can for example be experienced when sitting in a heated lobby during winter and the entrance door is suddenly opened. In this case the cold air will first be felt by ones feet as a result of the outside air propagating as a gravity current along the floor of the room.
   BULLET::::- In Chapter 22 of Charles Dickens' "David Copperfield", Steerforth declares: "As to fitfulness, I have never learnt the art of binding myself to any of the wheels on which the Ixions of these days are turning round and round."
  
  BULLET::::- In the Epilogue to "Moby-Dick", Ishmael, the only surviving crewmember at the sinking of the "Pequod", likens himself to "another Ixion."
  
  BULLET::::- In Guillaume Apollinaire's poem Vendémiaire, "...open-air chimneys impregnate the clouds/As once did the mechanical Ixion" (“... cheminées à ciel ouvert engrossent les nuées/Comme fit autrefois l’Ixion mécanique”)
   Section::::Production.
  