Fluent Technology Aides Guinness in Long-standing Debate: Do Bubbles in a Glass of Guinness Go Down? Simulation Software Proves Once and For All, Bubbles Go Up.... And Down!
Lebanon, New Hampshire – Computer simulation has settled a long-standing mystery haunting pubs and perplexed beer drinkers for centuries. Why do the bubbles in a glass of Guinness beer go down instead of up? Despite the common knowledge that bubbles float up, beer drinkers over the ages have argued, even after an evening of studying the issue, that a large portion of the bubbles actually move downwards.
Professor Clive Fletcher and his students at the University of New South Wales, Sydney, Australia, have used the latest industrial simulation methods to solve this mystery. The research team simulated the motion of the bubbles using FLUENT computational fluid dynamics (CFD) software from Fluent Incorporated to attack the problem head-on, so to speak. CFD simulations allow engineers to graphically depict fluid flows, pressure, temperature, and chemical concentration at any location, making it possible to quickly gain a better understanding of any problem involving fluid flow.
Fletcher's team used this software to simulate the motion of the bubbles and discovered that, as expected, most bubbles do move upwards. The bubbles in the center of the glass, free from the effects of the wall, move upwards most quickly and drag liquid with them. But the liquid moving up in the center of the glass, having nowhere else to go, must eventually turn towards the walls and start to move downward. The liquid moving downward near the walls tries to drag down bubbles with it. Larger bubbles have sufficient buoyancy to resist but smaller bubbles (less than 0.05 mm) are continuously dragged to the bottom of the glass.
The animation, which is based on the actual physics, clearly shows the bubbles moving downwards around the edges of the glass. Of course, the primary use of FLUENT CFD software is solving far more serious fluid flow problems, optimizing vehicle aerodynamics, speeding up the mixing process in chemical reactors and improving the performance of ventilation fans, for example. From answering the perplexing Guinness riddle to helping design the escape vehicle for the International Space Station (NASA), CFD software is making it possible to gain a much better understanding of our environment.
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