Stanford Report, April 9, 2002
Yacht research initiative explores science of sailing
BY DAWN LEVY
Research is rarely smooth sailing, but a group of Stanford scientists has launched a new initiative to make it so -- literally. A handful of yachting enthusiasts has established the Stanford Yacht Research (SYR) initiative to bring high tech to the high seas.
These Team New Zealand boats, NZL 57 and NZL 60, raced in the America's Cup 2000. They sport sails designed in part by Burns Fallow, whose April 17 talk is the first public event of the Stanford Yacht Research initiative. Photo courtesy of Team New Zealand
"We use advanced computational techniques to analyze the performance of sails and hulls and help improve their design," says SYR co-founder Margot Gerritsen, an assistant professor of petroleum engineering who has been at Stanford since September. She was formerly a member of the Yacht Research Unit at the University of Auckland in New Zealand. "We collaborate with the competitive and recreational yachting industry. The simulation of flows past sails is challenging, especially in reaching conditions where the flow is separated. The fact that sails are flexible, not rigid like an airplane wing, adds extra complexity."
The group is working with Team New Zealand, the defender of the America's Cup, on performance analysis of sail designs. The group's first public event is a lecture by Burns Fallow, lead sail designer for Team New Zealand, which will be held at noon April 17 in the Green Earth Sciences Building, Room 104. The talk, titled "The Design of America's Cup Sails," is free and open to the public.
"Team New Zealand has won the last two America's Cup races -- and quite substantially," says Gerritsen. "They blew the other folks out of the water."
The goal is to do so again during the next America's Cup race in 2003, and that takes a lot of science. Fallow is right in the middle of creating new sail designs, says Gerritsen, whose entry into the world of yachting came five years ago as a faculty member at the University of Auckland when an undergraduate approached her looking for an adviser in computational fluid dynamics, her area of expertise. That student, Steve Collie, stayed on for doctoral studies and now works with Team New Zealand on computer simulations of air flow past upwind and downwind sails.
Established in 1851, the America's Cup race is held approximately every four years in the defender's country. For 132 years, the Cup stayed in America. In 1983, however, the Australians won it -- only to have the Americans win it back in 1987. The outcome of a controversial race in 1988 had to be decided in court -- America prevailed over New Zealand -- and provoked redefinition of the race rules. In 1992, Americans won. But in 1995, Team New Zealand beat the American defender in San Diego and successfully defended in Auckland in 2000.
"For a small country like New Zealand, the 2000 defense was sensational," Gerritsen says. "I jumped at the chance to work with Team New Zealand." She says working on America's Cup research is "extremely exciting but challenging." Each team comes up with two new hull designs per year and numerous sail designs. The design constraints imposed by the America's Cup rules result in small design differences -- and narrow winning margins. Computational sail performance analysis is increasingly important in the sail design process.
After simulated designs are turned into real Team New Zealand sails, a wind tunnel in New Zealand puts them to the test. Gerritsen continues to advise Collie, who will be at Stanford this summer, on turbulence models to simulate the separated air flows that occur in downwind sailing.
Stanford partners in the initiative include aeronautics and astronautics Professor Antony Jameson, who developed software codes and numerical methods for the simulations and optimizations, and his doctoral student Sriram Shankaran, who analyzes upwind sails and is developing a method to optimize their shapes.
Research and development engineer Gianluca Iaccarino of the Center of Turbulence Research and one of his doctoral students, Tyler Doyle, are using commercial fluid dynamics software packages to analyze flow past sails. Doyle, the son of the founder of Doyle Sailmakers of Marblehead, Mass., is working on sail design for a three-masted superyacht. Iaccarino and Doyle are hoping to use optimization algorithms to improve the design of the sails.
Other collaborators include Luigi Martinelli of Princeton and Nick Holroyd of Team New Zealand, who specialize in hull design.
Stanford researchers hope to extend their work to hull design soon.
"Ultimately, we'd like to optimize the complete yacht, using hull
and sail analysis in combination with yacht velocity prediction
programs," Gerritsen says. "That will keep us busy for many years