Bubbling beer: Still from a video clip of beer bubbling and foaming while being poured in a glass.

Credit: CSIRO

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SYDNEY: Computer scientists have captured the maths described in pouring a pint of beer to create the most realistic yet computer animation of a virtual beer.

The physics of bubble creation in carbonated drinks like beer is complex, said Mahesh Prakash a computational fluid dynamics researcher with Australian government research body CSIRO in Melbourne.

"As you pour beer into a glass, you see bubbles appearing on what are called nucleation sites, where the glass isn't quite smooth," said Prakash. "The bubbles expand to a certain size then rise up in streams to the surface, where they bump into each other and form a raft of foam that floats on the top."

Bubbling and frothing liquids

Until now, nobody had been able to accurately capture this in the form of computer graphics, but Prakash's team – working with one of the world's largest computer game graphics developers, The Electronics and Telecommunications Research Institute in South Korea – have now modeled the maths behind the pouring of a pint of beer, and described the process in computer software.

Clever maths called smoothed particle hydrodynamics (SPH) helps the software do its job by working smarter not harder; the software uses less computer power and takes less time to get better results than other special effects software against which it has been benchmarked, said the researchers.

They will reveal the results of the four-year research project next week in San Diego, California, at SIGGRAPH 07, the world's largest computer graphics conference.

The researchers hope that the software – which is also able to model all manner of bubbling and frothing liquids – will allow movie makers, film production houses and others to create super-realistic special effects.

Cheaper solution

CSIRO's commercialisation manager Andrew Dingjan said that the fluid animation software will be much cheaper than other fluid animation software, so should bring it within the reach of smaller production houses.

"Big Hollywood studios spend vast sums on single-use solutions when they make blockbusters like 'Poseidon' and 'The Perfect Storm' but we'd like our software to make realistic special effects easier to come by."

Earlier this year another group of researchers succeeded in modelling the foam on beer with equations. As reported in the British journal Nature, physicists Robert MacPherson, at the Institute for Advanced Study in New Jersey, and David Srolovitz, at Yeshiva University, New York discovered that beer foam, is a 'microstructure with complex interfaces'. In other words: a cellular structure comprising networks of gas-filled bubbles separated by liquid.

The walls of these bubbles move as a result of surface tension – and the speed at which they move is related to the curvature of the bubbles. As a result of this movement, the bubbles merge and the structure "coarsens," they said – with the profound conclusion that the foam settles and eventually disappears.

See a short 'photoreal' animation of beer and other fluids that CSIRO mathematicians have achieved using computational fluid dynamics here. (Courtesy of CSIRO, requires broadband and Windows Media Player.)