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Zero carbon emissions? It's child's play

It's hard to pigeonhole Paul Linden. To do so you'd need to explain a Scotch bottle in his office in the Jacobs School's Department of Mechanical and Aerospace Engineering (MAE) filled with two immiscible fluids. Designer of a children's museum and sustainability engineer probably wouldn't come to mind.

After earning a Ph.D. in 1971 in applied mathematics in theoretical physics from the University of Cambridge in the United Kingdom , the native Australian studied ocean currents. He explains how temperature and salinity gradients produce unexpected convections. That's where the Scotch bottle comes in. He tips it left and then right. The less dense, yellowish upper layer of kerosene sloshes faster than the bottom, aqueous layer. Fluid mechanics explains why.

"I've always been interested in flows of all kinds of fluids," says Linden , chair of the MAE Department. "Density differences in different fluids generate buoyancy forces, which are important determinants of ocean flows, fluid flows in a bottle, and even natural ventilation in commercial buildings."

Linden modeled ambient air currents as part of his contribution to design of the new Children's Museum of San Diego. The California Energy Commission funded Linden's participation with design engineers at Rob Wellington Quigley, a California architecture firm.

The $18 million atrium-style building won't have conventional heating and cooling. Instead, it will rely on computer-controlled windows and Linden's sophisticated model of the prevailing breezes in the city's Marina District that will pass through those windows as they open and close under automatic control.

A 92-foot-tall elevator tower will act as a cooling chimney exhausting interior air as sunlight warms it. During the hottest weeks of the year, outside air will replace the inside air 10 times per hour.

"We simply can't sustain our existing carbon-based economy," Linden says. "And that's where fluid mechanics comes in: it helps us design intelligent buildings with great comfort without burning fuels."