Shower power. (Physical news).When a flimsy shower curtain "attacked" David Schmidt one morning, he peeled the sticky plastic off his bare thigh and decided to solve the mystery of clingy wet curtains. Schmidt, a mechanical engineering professor at the University of Massachusetts The system includes UMass Amherst, UMass Boston, UMass Dartmouth (affiliated with Cape Cod Community College), UMass Lowell, and the UMass Medical School. It also has an online school called UMassOnline. in Amherst, may be the perfect sleuth to do it. Until now, says Schmidt, scientists have offered two hypotheses, or educated guesses, to explain menacing shower curtains: "It always came down to one person's opinion versus another's," he says. Some scientists have claimed it's the Bernoulli effect Bernoulli effect n. The phenomenon of internal pressure reduction with increased stream velocity in a fluid. [After Daniel Bernoulli. : as water, air, and other fluids accelerate (speed up), surrounding air pressure drops, creating lift (upward force). In other words Adv. 1. in other words - otherwise stated; "in other words, we are broke" put differently , the same forces that cause airplanes to soar also make shower curtains billow. Other scientists have said it's the chimney effect: as hot air in the shower rises, cool air outside the shower rushes in to fill the void, drawing the curtain with it. To study the forces at work, Schmidt drafted a computer model of a typical shower and divided the area into 50,000 tiny tetrahedral tet·ra·he·dral adj. 1. Of or relating to a tetrahedron. 2. Having four faces. tet cells, or pyramid-like sections. Then he let the software crunch numbers for 50 hours. To record what happens in each of the cells during 30 seconds of shower time, the program used computational fluid dynamics Computational fluid dynamics The numerical approximation to the solution of mathematical models of fluid flow and heat transfer. Computational fluid dynamics is one of the tools (in addition to experimental and theoretical methods) available to solve , complex math equations that explain how whirls of air and water react to pressure and motion. After 1.5 trillion calculations, the program spit out Verb 1. spit out - spit up in an explosive manner splutter, sputter cough out, cough up, expectorate, spit up, spit out - discharge (phlegm or sputum) from the lungs and out of the mouth 2. a colorful map of shower forces. To Schmidt's surprise, it looked like a tropical storm tropical storm n. A cyclonic storm having winds ranging from approximately 48 to 121 kilometers (30 to 75 miles) per hour. tropical storm (see diagram, above). [ILLUSTRATION OMITTED] It turns out, a curtain billows and clings because a shower stall is what engineers call a "driven cavity." Imagine the tub bottom as a moving treadmill. The motion forces the air and spray in the shower to rotate. The result: a vortex (swirling cylinder of fluid) that spins like a sideways hurricane. The vortex in the shower has a low-pressure center--and that sucks in the shower curtain. The sucking force is weak, though. To thwart a shower curtain attack, use a heavy curtain or one weighted with magnets. [ILLUSTRATION OMITTED] Caption: (Top) 1. Spray causes air to flow down from the shower head. 2. Air bounces off hard shower walls; ceiling forces the air back toward shower head. 3. Air currents swirl into a vortex. Its low-pressure center sucks in nearby air (above)--and the shower curtain. |
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