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NEWS RELEASE

JACOBS SCHOOL SCIENTIST LOOKS TO NATURE FOR INSPIRATION IN DESIGNING A NEW CLASS OF FLEXIBLE SURFACES FOR NAVY VEHICLES

July 9, 2003 -- Researchers at the University of California, San Diego's Jacobs School of Engineering are working with the U.S. Navy to develop a new type of flexible surface, known as a "compliant coating," that holds the potential to greatly reduce submarine noise and enable ships to travel faster and consume less fuel. Prof. Thomas Bewley, director of the UCSD Flow Control Lab, has received a prestigious ONR (Office of Naval Research) Young Investigator award to design a "tensegrity fabric" in order to make such new high-performance aquatic vehicles a reality.

The underlying concept behind the project is to stretch a semi-permeable membrane (Figure 2.) over a very thin, flexible substructure to form a unified system that passively changes shape in response to pressure and friction fluctuations imparted by the flow past the vehicle without sensors, computers, or electricity in order to reduce drag and noise by dampening the turbulent flow structures near the vehicle surface. In this way, the tensegrity fabric behaves very much like the forgiving skin of a dolphin, which has significant surface compliance properties which have not, to date, been emulated in Navy designs.

Tensegrity Fabric

This compliant skin can be tailored to meet a variety of desired specifications, and can be retrofit over existing vehicles without costly redesign. For ships, the compliant coating can reduce drag, allowing for higher speeds and less fuel consumption. For submarines, it is less about drag reduction and more about noise mitigation. By dampening the vortices that collide with the submarine's surface, the tensegrity fabric significantly reduces noise and improves the submerged vehicle's ability to conceal itself from enemies.

Like the notion of a compliant skin, the tensegrity paradigm itself also has ties to nature, as it provides the molecular foundation for spider fiber, nature's strongest material per unit mass. Tensegrity cells (Figure 1.) are self-supported pretensioned structures comprised of a collection of rods interconnected by tendons. The rigid rods (under compression) are typically of a lightweight composite material, while the tendons (under tension) are typically of a flexible Kevlar or Nickel-Titanium material. By interconnecting millimeter-scale tensegrity cells into extensive tensegrity plate-type structures (leveraging modest extensions to modern textile manufacturing machines whilst incorporating compressive elements into the weave), Bewley and his coworkers at UCSD are designing malleable substructures that can be precisely tuned, by adjusting the stiffness, mass, damping, and orientation of the various rods and tendons, to respond to the continuous fluctuations of the ocean flow past the vessel.

Bewley's UCSD Flow Control Lab uses advanced analysis techniques and high-performance computers to create representative mathematical models and accurate numerical simulations in order to validate the tensegrity fabric concept and explore the large parameter space capable with this design to optimize the tensegrity fabric system, paving the way for future manufacturing and implementation of this novel approach to the compliant surface problem.

Contact: Troy Anderson, 858-822-3075, tdanderson@ucsd.edu

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