Oliver Fringer
Oliver Fringer has a
different perspective than most
people when he visits beaches in the San Francisco Bay area, where
he lives. That’s because he’s made his reputation
creating computer models of ocean activity in coastal areas.
“I always look at the way the waves and small ripples propagate” as they break across the shore, says Fringer, a DOE CSGF fellow from 1997 to 2001.
“They do it in the same way large waves do,” and “you can describe how very large nonlinear waves interact by describing how those small waves interact.”
Fringer is an assistant professor of environmental fluid mechanics and hydrology at Stanford University, where he earned his master’s degree in aeronautics and astronautics in 1996 and his doctoral degree in civil and environmental engineering in 2003. Fringer was serving a postdoctoral fellowship at Stanford when he developed what has become the centerpiece of his academic reputation and research: the Stanford Unstructured Nonhydrostatic Terrain-Following Adaptive Navier-Stokes Simulator, or SUNTANS.
Fringer’s model is different because it simulates nonhydrostatic pressure. Most ocean simulation codes have been hydrostatic because most ocean flow is long and horizontal, Fringer says. That’s fine for global and regional ocean circulation, but it’s less accurate when modeling wave action along coastal areas, where nonhydrostatic pressure plays a bigger role. SUNTANS, which is supported by the Office of Naval Research, simulates the massive internal waves that begin deep in the ocean, then gain strength as they rise and break near the shore.
However, nonhydrostatic models make huge demands on computer resources. “The reason traditional models haven’t gotten into nonhydrostatic pressure is you have to solve the three-dimensional elliptic equation. It’s very expensive to solve elliptic problems in the ocean,” Fringer says. Ten years ago, a simulation like SUNTANS would have been impossible, but researchers have since found ways to solve the 3D elliptic equation more efficiently.
SUNTANS can model flows of any coast, river or estuary, Fringer says. The graduate students he supervises use the basic hydrodynamic kernel he devised to study sediment transport, internal waves in the South China Sea, and other ocean activity.
Such models can be instrumental in understanding how pollutants move through the ocean and how weather systems form. “The ultimate goal is to predict weather and climate,” Fringer says. “To do that you have to be able to accurately model the interaction of the ocean and atmosphere. To do that, you have to understand how energy moves around the ocean in the form of internal waves.”
Part of Fringer’s current research focuses on integrating SUNTANS with the Regional Ocean Modeling System (ROMS), a University of California – Los Angeles project, to simulate ocean activity over a larger range of space and time.
Fringer’s interest in research was inspired by his boyhood remote-control plane hobby and his contact with a Massachusetts Institute of Technology aerospace engineering graduate student. Now, Fringer’s profession already is influencing Avery, the daughter his wife, mechanical engineer Krista Donaldson, gave birth to in June.
“Poor Avery,” Fringer laughed. “Whenever I give her a bath, I always tell her about fluid mechanics.”
