Whale-Inspired Rotor Blades Could Boost Ocean Energy Harvesting
A variety of turbine blades with bumps on them modeled after humpback fin tubercles.
CREDIT: Mark Murray.
Underwater turbines that have bumpy rotor blades modeled after humpback whale flippers could more efficiently convert energy from tidal flows into electricity, scientists say.
Despite their large size, humpback whales are unusually acrobatic. Other whales their size typically just open their mouths and cruise into food to capture it, but humpback whales often capture schools of fish by swimming in shrinking circles below them, exhaling bubbles that confine their prey like nets, and then swimming upward with mouths agape to swallow thousands of targets at once.
The edges of humpback whale flippers possess bumps called tubercles, and scientists wondered if these protuberances helped them maneuver. Mechanical engineer Mark Murray at the U.S. Naval Academy and his colleagues found that such bumps improved hydrodynamic performance by increasing the maximum amount of lift a flipper produces.
By adding bumps to the leading edges of turbine blades, Murray and his colleagues discovered they could extract energy at low speeds much more effectively. At the same time, the bumps did not degrade performance in high-speed flows or increase the mechanical complexity of the turbines. Such bumps would probably not help airplane wings , however, as they only seem to assist in certain types of flows, such as water.
The lessons the researchers learned from these whales could help draw energy from the low speeds associated with many tidal flows. The researchers want to see if tubercles can also improve underwater turbines optimized in other ways for extracting energy from low-speed flows, and what number, size, placement and shape of bumps might best enhance performance, Murray told TechNewsDaily.
Ocean engineers Timothy Gruber and David Fredriksson, along with Murray and their colleagues, detailed their findings Nov. 22 at the American Physical Society's Division of Fluid Dynamics meeting in Long Beach, Calif.