Applied mathematician's solution for reducing drag on a vessel works in computer simulation; engineering professor is putting the calculations to the test
From amateur sailing enthusiasts to the U.S. Navy, everyone wants to talk with George Karniadakis about how to make watercraft go faster.
Applied mathematics professor Karniadakis (at left) has demonstrated a method to make surfaces more slippery, which has potential applications for any flowing fluid, from water past a ship, oil in a pipeline, and air against an aircraft.
"We created some sort of shield close to the skin," Karniadakis said.
Karniadakis showed that by creating traveling waves close to a surface, drag can be reduced by at least 30 percent. The key is that the traveling waves must be perpendicular to the flow of the fluid.
The success of the perpendicular waves in computer simulations surprised Karniadakis and just about everyone else; the work runs counter to conventional wisdom. Science magazine published his work last May with Yiqing Du, who received his doctorate in 1999 and who now is at Microsoft.
Karniadakis designs algorithms — mathematical patterns— to solve problems such as how to reduce drag on a vessel. His computer simulations show how to dramatically cut down drag, but it remains to be seen whether they work in real life.
The preliminary real-world experiments are being conducted by Kenneth Breuer, associate professor of engineering, in a water tunnel 6 feet long by 3 feet wide by a couple of inches high. The channel flow allows him to do careful measurements with Karniadakis’ calculations. In addition, the Naval Undersea Warfare Center in Newport is doing complementary experiments, more applied than fundamental, in a larger water tunnel.
"If they’re successful, we will be doing a very big experiment in the ocean in two years. That will take place in a Navy lab in the Bahamas" and involve a 20-foot-long mini-submarine built for testing purposes, Breuer said.
In addition, Karniadakis is working with colleagues at the Massachusetts Institute of Technology to apply the electromagnetic tiles to an unmanned vessel. The goal is to speed the vessel so that it can make a trans-Atlantic crossing without refueling.
The experiments all involve magnets and electrodes on small tiles. The force created by the electromagnetic field creates the perpendicular waves that cut down loops of turbulence that rise from a surface.
"The object of our experiment is to realize physically what Karniadakis has computed on the computer; to face all of the sort of real-life problems that come," Breuer said. "For example, he has assumed certain configurations which in real life are actually hard to build. Also, salt water is corrosive. Calculations don’t really concern themselves with that. And electronics are quite complicated, and building them in real life has its challenges."
Breuer hopes to show encouraging results by early April, when the funding comes up for review by the Defense Advanced Research Projects Agency (DARPA) through the Office of Naval Research. Currently, the Brown professors are working with a $366,000 grant. If the work shows promise over the next two months, DARPA may award $527,000 through February 2004.
"It’s a very critical time," Breuer said.