Stingrays are able to glide so effortlessly through the water thanks in part to their protruding eyes and mouth.

Sea rays, including stingrays and skates, are noted for their streamlined body and flexible pectoral fins. These features offer obvious hydrodynamic benefits, but some scientists assumed their protruding eyes and mouth were hindrances.

In a new study, scientists modeled the effects of these protuberances on a variety of forces, such as pressure and vorticity, that influence propulsion.

Their analysis -- published Tuesday in the journal Physics of Fluids -- showed a stingray's protruding eyes and mouth actually help it move through the ocean water more efficiently.

Researchers began by building a model of the stingray's self-propelled flexible plate. They clamped the front end of the plate and programmed it to perform rhythmic, up-and-down oscillations -- the same movement pattern stingrays use to swim.

Next, the researchers added rigid plates to the model to mimic the effects of the stingray's eyes and mouth, comparing the hydrodynamic efficiency of models with and without the added plates.

"Managing random fish swimming and isolating the desired purpose of measurement from numerous factors are difficult," study corresponding author Hyung Jin Sung said in a press release.

"To overcome these limitations, the penalty immersed boundary method was adopted to find the hydrodynamic benefits of the protruding eyes and mouth," said Sung, a researcher at the Korea Advanced Institute of Science and Technology.

Data showed both the stingray's eyes and mouth yielded a front-back vortex of flow that increased the negative pressure in front of its body, easing its path through the water.

The eyes and mouth of a stingray help it swim more efficiently, researchers found in a modeling study. Illustration by Qi-an Mao

A side-to-side vortex created by the protuberances also boosted negative pressure above and below the stingray, the researchers said.

According to the model, these pressure shifts provided the stingray with greater thrust and accelerated cruising.

In total, scientists determined the stingray's protruding eyes and mouth boost propulsion efficiency between 10% and 20%.

The insights provided by the modeling effort could be used to design more hydrodynamic autonomous underwater vehicles, according to the researchers.

Related Links
Water News - Science, Technology and Politics

Tweet

Thanks for being here; We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain. With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords. Our news coverage takes time and effort to publish 365 days a year. If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.
SpaceDaily Contributor $5 Billed Once credit card or paypal		SpaceDaily Monthly Supporter $5 Billed Monthly paypal only

Ocean surface climates may disappear by 2100: study
Paris (AFP) Aug 26, 2021
Up to 95 percent of Earth's ocean surface will have changed by the end of the century unless humanity reins in its carbon emissions, according to research published Thursday. Ocean surface climates, defined by surface water temperature, acidity and the concentration of the mineral aragonite - which many marine animals use to form bones and shell - support the vast majority of sea life. The world's seas have absorbed around a third of all carbon pollution produced since the Industrial Revolut ... read more