Saturday, November 28

Fluid dynamics may help drones capture a dolphin’s breath in midair

If you’ve ever had trouble catching your
breath, try catching a dolphin’s.

The plume produced when dolphins come up
for air could reveal information about their health. But capturing samples of the
spray from agile, skittish wild dolphins is challenging. To make the task
easier, a team of engineers has characterized the flow of a dolphin’s chuff, a forceful exhale that sends water, air and mucus
hurtling skyward.

High-speed video of captive Atlantic
bottlenose dolphins reveals that each chuff lasts around a quarter of a second,
beginning with a brief spurt of water flung off the top of the blowhole, says engineer
Alvin Ngo of Oklahoma State University in Stillwater. Then comes a second wave:
the exhale. That powerful outflow produces a turbulent jet moving at a maximum speed
of nearly 100 kilometers per hour, Ngo and colleagues reported November 24 in
Seattle at the American Physical Society’s Division of Fluid Dynamics meeting.

The expelled mucus contains health indicators, particularly the stress hormone cortisol. So understanding these chuffs could help scientists design drones that would swoop in to catch the spray and reveal, for example, whether a pod is stressed by human activity. Researchers previously have used drones to sample spouts from whales (SN: 10/20/15), but dolphins produce less spray, complicating efforts.

Gobs of mucus go flying when Atlantic bottlenose dolphins breathe. Studying the spray could aid attempts to collect wild dolphins’ mucus and monitor their health.