As the “Summer of Racing” gets underway in San Francisco Bay, Dr. Len Imas of Stevens has a front-row seat for some of the most exciting races in the world.
As a recognized specialist in application of computational fluid dynamics methods in yacht R&D, Imas is helping New Zealand’s top sailors in their attempt to claim professional yachting’s biggest prize – the America’s Cup, the oldest trophy in international sport and the most high-profile, competitive and difficult to win.
Imas, an associate professor of ocean engineering, is a hydrodynamics expert and modeling engineer for Emirates Team New Zealand’s design group, which developed and built the state-of-the-art, high-performance sailboat the team will use in the 2013 America’s Cup, the 34th edition of the competition and the first-ever inshore race. New Zealand is a perennial power in the America’s Cup, which is held once every four years and features only the top-ranked teams in the world.
Imas has also participated in three prior America’s Cups on behalf of a number of different teams. His know-how of computer modeling and aero-hydrodynamics has helped support recent advances in sailboat technology.
Imas earned his Ph.D. in Numerical Hydrodynamics from Massachusetts Institute of Technology and a B.S. / M.Eng. in Aeronautical Engineering from Rensselaer and has been a member of the Stevens faculty since 2003. An amateur sailor, he initially became interested in sailing yacht design and aero-hydromechanics as a graduate student. After a stint working in fluid mechanics in the defense and oil industries, he refocused his career on academia but has remained continuously engaged in racing yacht R&D, specifically R&D involving computer modeling applications. Today, he is viewed as a specialist in the field.
“Technically, a sailboat is a very interesting machine in that it is driven only by wind but its aerodynamics and hydrodynamics are quite complex because of their interaction,” Imas said. “A sailing yacht has to operate across a wide range of wind speeds and directions, and sea states, so it is a challenging R&D exercise to try to understand and model the physics behind it, as well as optimize any subsequent design.”
In this campaign, Imas applied his computer modeling knowledge to the development of a super-fast AC72 catamaran, the sailboat class chosen for the 2013 America’s Cup.
With a lightweight and cutting-edge design, the AC72 can reach speeds approaching 45 miles per hour due to several unique features. The “flying boat” has a giant, 140 foot tall rigid wing, as well as hydrofoils – little underwater wings which reduce overall drag by enabling the boat to sail with its main hulls entirely above the water. At 72 feet long and 13,000 pounds, it is manned by 11 sailors.
“Yachts used in the 2007 America’s Cup in Spain reached top speeds of only around 15 miles per hour,” said Imas. “When the boat class shifted form from a monohull to the current catamaran, incorporating new technology, there was a huge speed leap.”
Imas’ specialty – computational hydrodynamics – helped the Emirates Team New Zealand designers develop the optimal shape of the sailboat to reduce drag and maximize speed by providing insights into how fluid flows around the yacht. This is accomplished by conducting virtual computer experiments which simulated various flow conditions, which in turn permit the prediction of forces around the boat.
Imas will spend part of the summer in California as Emirates Team New Zealand and two other challengers compete to race against the defending champion, Oracle Team USA, in the America’s Cup Finals in September.
On campus, Imas uses his unique experiences to continuously enhance the curriculum of Stevens classes he teaches, focused on computer-aided ship design, hydrodynamics, numerical hydrodynamics, and yacht design.
Imas finds students are extremely engaged and responsive when they see state-of-the-art tools and techniques applied in a real-world engineering context. For example, last year, a Stevens senior design team even designed a 60-foot foil-assisted catamaran, using some of the same modeling tools.
“In some shape or form I tend to teach some of the content that I apply in actual yacht R&D,” Imas said. “The students appreciate the integration of current methods of computer modeling and how they apply to professional sports such as high performance sailing.”
While current Stevens students benefit from Imas’ singular expertise on racing yachts R&D in their coursework, the university also has a deep legacy connection to the America’s Cup – starting in 1851 when the Yacht America, built by the Stevens founding family, initiated the America’s Cup competition.
Decades later, in the 1930s, Stevens Mechanical Engineering Professor Kenneth S.M. Davidson founded the Experimental Towing Tank at Stevens, one of the first tow tank facilities for maritime research in the nation. Among its many claims to fame – it was critical in advancing the design and engineering of ferry crafts, seaplanes, destroyers and even submarines – the Experimental Towing Tank revolutionized how sailboats were built. In fact, the winner of the 1937 America’s Cup was tested and developed in the Experimental Towing Tank, using scale model experiments to realistically study its behavior in various wind and wave conditions and create the optimal configuration for speed. Many subsequent America’s Cup and other grand prix racing yacht models were also tested in the towing tank. Information derived from these studies contributed greatly to present day understanding of sailboat hydromechanics.
The Experimental Towing Tank was rebuilt and renamed the Davidson Laboratory in 1958. Today – as one of the world’s leading facilities in the field – its researchers have continued to pioneer numerous advances in ship design and naval architecture and contributed significantly to our basic understanding of maritime security and the marine environment.
Photos courtesy of America's Cup