Exploring the characteristics of viscoelastic fluids

Feb 04, 2010 By Miranda Marquit feature

(PhysOrg.com) -- There are many microorganisms out there, navigating through complex biological fluids. “One of the most common migrations takes place with spermatozoa as it navigates the female reproductive tract,” Joseph Teran tells PhysOrg.com. “But there are other organisms that move through difficult environments as well, and we want to gain a better understanding of how these organisms move through viscoelastic fluids, like those found in biology.”

Teran works in the Department of Mathematics at the University of California, Los Angeles. He collaborated with Lisa Fauci at Tulane University and Michael Shelley at New York University to create a depicting what happens when a free swimmer moves through a viscoelastic fluid. Their results can be seen in : “Viscoelastic Fluid Response Can Increase the Speed and Efficiency of a Free Swimmer.”

“Our experiment is a computer simulation that is more representative of the real medium than simpler models relying on a more standard Newtonian fluid. The simpler models work out nice mathematically, but they are not a very accurate description of the physics that are happening,” Teran explains.

With the simpler models, a wave is often depicted as moving through the fluid, with no head or tail. Additionally, these simpler models only account for the viscosity of the fluids, rather than including an element of elasticity. Teran and his peers added a free swimmer with a head and a tail, and included information representing tail undulations. They also used a viscoelastic Boger fluid in their calculations to more accurately represent the actual conditions.

“What we found defies conventional wisdom,” Teran says. “When you think of a viscous fluid, like mud or honey, the fact that it is hard to swim through comes to mind. It’s inherently resistant to shear, and it is more likely to stop you. If you add elasticity, it seems like it should be even harder to swim through, since a viscoelastic fluid has a memory and resists changing shape. However, we found that a free swimmer ends up going faster in a viscoelastic fluid than a just plain viscous fluid.”

The answer lies in the tail motion of the swimmer. “If you accentuate the tail motion, as seen in a lot of microscopic swimmers, you see them able to move faster because they can use the in the fluid to sort of push off. It’s leverage for use in biology.”

Teran believes that the work he had done with Fauci and Shelley has implications for a number of biological applications. “The most obvious is in reproduction and fertility,” he points out. “Understanding how sperm locomote could be helpful in figuring out how to aid in reproduction. Teran also insists that understanding how these fluids work could have other uses in some engineering and biological functions. “There are a wide range of applications for fluids, and understanding their dynamics could be useful.”

Next, Teran, Fauci and Shelley hope to improve their model. “So far, we have only done this in a two dimension model,” Teran says. “We also used a Boger fluid, which is a kind of crude viscoelastic fluid. It’s simplistic and easier to tune to a given physical setting. But now that we know our model works, we want to ramp it up, improving the computer code. Three dimensional modeling is one natural extension, as is using a more complex fluid to even more accurately represent real world conditions.”

Hopefully, a better model will provide scientists and mathematicians with a better understanding of dynamics. “Fundamentally, this could be a real help to science,” Teran says, “and there are applications that could come out of this better understanding.”

Explore further: Seeking 'absolute zero', copper cube gets chillingly close

More information: Joseph Teran, Lisa Fauci, Mischael Shelley, “Viscoelastic Fluid Response Can Increase the Speed and Efficiency of a Free Swimmer,” Physical Review Letters (2010). Available online: link.aps.org/doi/10.1103/PhysRevLett.104.038101

4.8 /5 (10 votes)

Related Stories

How to Rip a Fluid

Jun 01, 2007

In a simple experiment on a mixture of water, surfactant (soap), and an organic salt, two researchers working in the Pritchard Laboratories at Penn State have shown that a rigid object like a knife passes ...

Virtual swimmer to speed up athletes

Mar 30, 2006

CSIRO and the Australian Institute of Sport are using mathematics in a bid to speed up our top swimmers by testing changes to swimming strokes. The research will make use of the same software CSIRO uses for other fluid simulations ...

Mathematicians promise animation revolution

Mar 30, 2005

CSIRO mathematicians are combining art and science to solve one of the last big challenges in animation – fluids. They are aiming to develop techniques for fluid animations that are so realistic audiences wil ...

Researchers discover new way to control particle motion

Mar 17, 2008

Chemical engineers at The University of Texas at Austin have discovered a new way to control the motion of fluid particles through tiny channels, potentially aiding the development of micro- and nano-scale technologies such ...

NASA Know-How Helps Athletes Rocket Through Water

Feb 12, 2008

When a swimsuit manufacturer wanted to create a better fabric for competitive swimmers, it sought out some unlikely experts -- aerospace engineers at NASA's Langley Research Center in Hampton.

Recommended for you

Backpack physics: Smaller hikers carry heavier loads

5 hours ago

Hikers are generally advised that the weight of the packs they carry should correspond to their own size, with smaller individuals carrying lighter loads. Although petite backpackers might appreciate the ...

Extremely high-resolution magnetic resonance imaging

6 hours ago

For the first time, researchers have succeeded to detect a single hydrogen atom using magnetic resonance imaging, which signifies a huge increase in the technology's spatial resolution. In the future, single-atom ...

'Attosecond' science breakthrough

7 hours ago

Scientists from Queen's University Belfast have been involved in a groundbreaking discovery in the area of experimental physics that has implications for understanding how radiotherapy kills cancer cells, among other things.

User comments : 2

Adjust slider to filter visible comments by rank

Display comments: newest first

not rated yet Feb 16, 2010
This may explain why fish can move through water with relitive ease. Could be the vicoelastic layer on the skin. (slime).
not rated yet Mar 26, 2010
The Reynolds number associated with the motion of a fish might be on the order of 10^4 while for a spermatozoa it might be roughly 10^(-3). This non-dimensional quantity dictates how important inertial effects are vs. viscous effects. Due to this discrepancy the work above has absolutely no ramification for the motion of fish.