While they might be the bane of swimmer's existence during a beach holiday, jellyfish have given engineers an important new insight: how to build faster submarines and other underwater craft.
The oscillating, mesmerizing motion of a jellyfish propelling through water was previously thought to have been mostly due to the marine animal pushing against the water. Despite this popular notion, a team of scientists at Stanford suspected that this theory might not be the case and decided to put it to the test. They found that jellyfish actually suck water toward them, and then use the low pressure created by this motion to throttle them forward.
But from the get-go, the team already had a difficult barrier to overcome to observe their man o' war in motion: how to measure the movements of fluids around solid objects, which is extremely difficult to quantify.
"Interactions between solid objects are usually straightforward, like two billiard balls bouncing off each other, and therefore you can calculate the forces without much difficulty," explained John Dabiri, a professor of civil and environmental engineering and of mechanical engineering at Stanford, as well as one of the lead researchers in the study. "But in a fluid, every molecule is like a billiard ball and they are practically innumerable. There isn't a simple way to calculate all those interactions."
The team decided to apply an experimental method they came up with themselves, one which involved including a palpable "pressure variable" to serve as a visual, real-time stand-in for water molecules, and the effect a jellyfish pulse would have on them: tiny hollow glass beads.
Dabiri and his team placed the beads into an acrylic tank filled with water, with a small jellyfish following soon after for the scientists to observe. Two lasers were placed opposite each other at both ends of the tank to also aid in visibility for the researchers, and a digital camera was used to record the proceedings.
The findings Dabiri's study collected will be applied to how engineers approach designs for marine modes of travel.
"For nearly 100 years, it has been assumed that mimicking natural swimming meant finding ways to generate high pressures to push water backward for thrust," said Dabiri. "Now we realize we've had it backward, and so the search is on for ways to generate low-pressure suction to achieve more efficient underwater propulsion."
Check out some jellyfish in motion in the video below.
The team's research is outlined in an article published in the journal Nature Communications.
Via: Engadget
Photo: Yosuke Shimizu | Flickr
