(麻豆淫院Org.com) -- There are many microorganisms out there, navigating through complex biological fluids. 鈥淥ne of the most common migrations takes place with spermatozoa as it navigates the female reproductive tract,鈥� Joseph Teran tells 麻豆淫院Org.com. 鈥淏ut 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.鈥�

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 computer model depicting what happens when a free swimmer moves through a viscoelastic fluid. Their results can be seen in 麻豆淫院ical Review Letters: 鈥淰iscoelastic Fluid Response Can Increase the Speed and Efficiency of a Free Swimmer.鈥�

鈥淥ur 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,鈥� 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.

鈥淲hat we found defies conventional wisdom,鈥� Teran says. 鈥淲hen you think of a viscous fluid, like mud or honey, the fact that it is hard to swim through comes to mind. It鈥檚 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.鈥�

The answer lies in the tail motion of the swimmer. 鈥淚f 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 elasticity in the fluid to sort of push off. It鈥檚 leverage for use in biology.鈥�

Teran believes that the work he had done with Fauci and Shelley has implications for a number of biological applications. 鈥淭he most obvious is in reproduction and fertility,鈥� he points out. 鈥淯nderstanding 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. 鈥淭here are a wide range of applications for fluids, and understanding their dynamics could be useful.鈥�

Next, Teran, Fauci and Shelley hope to improve their model. 鈥淪o far, we have only done this in a two dimension model,鈥� Teran says. 鈥淲e also used a Boger fluid, which is a kind of crude viscoelastic fluid. It鈥檚 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.鈥�

Hopefully, a better model will provide scientists and mathematicians with a better understanding of fluid dynamics. 鈥淔undamentally, this could be a real help to science,鈥� Teran says, 鈥渁nd there are applications that could come out of this better understanding.鈥�

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