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New uses

Once the exclusive realm of aerospace engineers using airflow models to create new generations of wing designs, CFD gradually evolved in the early 1990s to become a tool to help designers of commercial and public buildings, starting first in Europe and Japan and eventually reaching the U.S. Still an expensive niche technology used only for select projects, CFD helps architects gauge the effectiveness of exotic HVAC systems, especially those used to regulate large open spaces like atria. The technology can also model the air quality within a proposed building or judge the effectiveness of new or nontraditional types of ventilation systems, such as the radiant flooring that will be used in the Clinton Center.

In addition to the Clinton Center, Flack + Kurtz has used CFD for a new dormitory at Dartmouth College, which also makes use of a radiant-heating and -cooling floor slab. “We’re trying to [air-] condition the people, not the space,” Nall says about the design goals of those projects. “People are not going to be walking on the ceiling, so we’re working on creating comfortable conditions in the zones of the buildings that are actually occupied. CFD is the only way we can get a handle on what’s going on in these spaces.” The only alternative, he says, would have been to build full-scale mock-ups of the structures and take physical readings—obviously a cost-prohibitive exercise.

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Flack + Kurtz isn’t the only engineering company to conduct CFD analyses on buildings. Steven Winter Associates in Norwalk, Connecticut, used CFD to help optimize the operation of an HVAC system with natural ventilation at the Adam Joseph Lewis Center for Environmental Studies at Oberlin College, a project designed byarchitect William McDonough, AIA. Architectural Energy Corporation (AEC), a Boulder, Colorado, engineering and design firm, worked with the Pittsburgh architecturefirm IKM to create an addition to the Phipps Conservatory and Botanical Gardens, in Pittsburgh. The addition (called the Tropical Forest Building) houses a rain forest, and the CFD analysis depicted not only temperatures and airflow, but also patterns of sunlight throughout the year. “Our clients are plants, which need the right amount of light, the right spectrum of light, and the right temperature,” says Michael Holtz, AIA, AEC’s president. “We’re looking at airflow to make sure we achieve acceptable conditions.” In addition, Arup, a London-based engineering company, used CFD to help remodel the air-conditioning system of the historic London Coliseum, the home of the English National Opera.

In each case, CFD provided “what-if” capabilities that helped architects and engineers reconcile environmental and design considerations. “Architects come to us with design objectives and CFD helps them develop a design that meets those objectives,” Holtz says. “Once a preliminary design is developed, CFD can then be used to evaluate its effectiveness.”

These capabilities are helping CFD find more widespread applications, especially for more innovative designs. “It gives us more freedom to play with new ideas,” says Jelena Srebric, assistant professor and CFD instructor at Pennsylvania State University’s department of architectural engineering. “CFD allows us to test [models and designs] that don’t yet exist.”