University of Iowa researchers have reported a key advance in the ease of flow and maneuverability for underwater vehicles.
In a new study, the research team outfitted the wings of an underwater hydrofoil with a series of coiled spires that, when activated, would unspool, reducing drag and creating more lift for the craft as water current was moved around it.
The technology comes from the lab of Caterina Lamuta , associate professor in the Department of Mechanical Engineering in the College of Engineering, who has been working on technology that mimics the skin, muscles, and tissue of an octopus. The goal is to build, and eventually deploy, underwater vehicles that move with ease in any underwater environment, with appendages that can reach into the smallest of spaces. The potential applications are numerous, ranging from inspecting undersea pipes to collecting deep-water specimens.
In this study, Lamuta's research group demonstrated a proof of concept for the coiled spires, which they call twisted spiral artificial muscles. These synthetic coils are designed to mimic an octopus' papillae muscles, which are located on the animal's skin and can be uncoiled on a moment's notice for camouflage and to aid movement when flow conditions change in the water.
The team modified a hydrofoil's wings with two rows of four twisted spiral artificial muscles, each one powered by two tiny electrical motors, called actuators. In experiments with water moving at different speeds, the researchers report the hydrofoil generated a lift up to 30% and reduced drag by up to 10% during certain maneuvers. With the increased lift and reduced drag, the hydrofoil displaced the water more easily during different flow conditions, even when the craft was tilted steeply against the direction of water flow.
"This study can help make unmanned underwater vehicles more efficient, using low-cost artificial muscles that are bioinspired by the motion of octopus papillae muscles. It can help save energy and improve the portability and maneuverability of seafaring vehicles," says Rabiu Mamman , a doctoral student in mechanical engineering in the College of Engineering and a graduate research assistant in IIHR Hydroscience & Engineering.
The authors say this is the first demonstration of an underwater flow control device powered by twisted artificial muscles.
The study, "Bioinspired active vortex generators for underwater flow control," was published online Aug. 26 in the journal Robotics Reports.
Lamuta is the study's corresponding author. Mamman is the paper's first author. Thilina Weerakkody, a doctoral student in Lamuta's lab, is a co-author.
The U.S. Office of Naval Research funded the research.
