CORVALLIS - A new age of high-speed, low-cost ship transport - with large vessels traveling at speeds of more than 70 miles per hour or going slower while cutting their fuel costs in half - may be possible with advanced technology designed to reduce the drag and friction forces on the hull of the ship.
The potential of this technology started with a patent in the early 1800s, and it was later studied seriously in the 1970s, but with little fruitful development. But the concept has recently become the focus of renewed research programs in the U.S. and around the world, and may be ready for real-world testing within a few years, scientists say.
The idea of a huge cargo vessel zipping across the ocean at speeds usually seen on freeways seems improbable, but it may actually be feasible with further advances in fundamental and applied research on ways to reduce the friction of a ship traveling in water, said James Liburdy, the James Welty Professor of Mechanical Engineering at Oregon State University.
"There are different ways of approaching this, with new types of ship designs such as hydrofoils or more conventional designs that use different technologies to reduce friction," Liburdy said. "There's quite a bit we still need to learn to make this concept work in actual marine usage, but we could be testing some designs within a few years."
The military has a special interest in this technology, to be able to speed supplies to remote sites around the world, Liburdy said. And there would also be important commercial shipping applications, which may focus on fuel savings as well as additional speed, or transporting of perishable products.
Some approaches are examining the injection of polymers into the water to speed travel - polymers are already being used to speed oil transport in the Alaskan pipeline. And the Office of Naval Research is supporting a collaborative research effort among OSU, other universities and private industry that's studying the use of "microbubbles" of air that are used to reduce the friction between a ship's hull and the water it moves through.
"Friction increases the faster a surface moves through a fluid, in this case a ship's hull through water," Liburdy said. "There's a very thin layer called the boundary layer where most of this friction occurs. This layer is only about 50 microns wide, less than the width of a human hair, at the speeds envisioned for these ships. So it's a technological challenge to create systems that can work at these small scales."
However, the recent advances in microtechnology at OSU and elsewhere are making possible some options that weren't realistic in past decades. Many related studies are under way at OSU through its Microproducts Breakthrough Institute and the Oregon Nanoscience and Microtechnologies Institute.
"The study of friction reduction in this type of setting actually first surfaced in the 1970s by Soviet scientists looking to improve the speeds of submarines and torpedoes," Liburdy said. "But some of the early tests, by the military and others, used fairly crude technologies that were limited and the results were not very convincing. So the whole idea gained little attention for the last 20 years."
That has changed, and the research interest in the U.S., Japan and elsewhere is now very active. At slow speeds, the use of microbubbles in a test chamber has been shown to reduce friction by as much as 80 percent, and in theory could allow large ships to travel at speeds of 70-100 miles per hour. In practice, such a system might work by pumping air through a micro-injector formed from porous plates on a ship's hull. This would send out extremely tiny bubbles, which would stream along the side of the ship and greatly reduce the friction of the ship's hull with the water.
"The fact that microbubbles can reduce a ship's drag is now very well accepted," Liburdy said. "But we still need to prove this can be affordable and practical in a real marine environment. And to achieve a truly cost-effective system, we must have a much better fundamental understanding of exactly how these bubbles form, function and reduce friction."
Another concept being studied is use of a "vortex generator," conceptually similar to a device already used on the wings of jet airplanes, that can trap and direct a spinning flow of bubbles immediately adjacent to the ship's surface where they are needed.
"There are still some key tissues we don't understand about the fluid mechanics of this process, and that's what our research is focused on," Liburdy said. "But we're making progress, and the potential value of a working system should be huge."