Fluid turbulence is often referred to as the last great unsolved problem of classical physics. Despite the importance of turbulence in varied scientific fields, the phenomenon is still poorly understood. One attempt at gaining a better understanding of turbulence focuses on the coherent structures seen in both experiment and direct numerical simulation(DNS) of fluid flows. Recent research by F. Waleffe and others has found exact stationary (in a moving frame) solutions to the Navier-Stokes equation that are linked to the coherent structures observed in turbulence. The study of these exact coherent states leads to a better understanding of the coherent structures and their role in the dynamics of turbulence.
The research in our group focuses on how these exact coherent states are affected by rheologically complex additives, such as polymers. It has been known since the 1940's that the addition of a very small amount of polymer (10-500 ppm) to a simple fluid can produce dramatic effects in turbulent flow without appreciably changing the properties measured in laminar flow. One of the more industrially important effects is drag reduction, the suppression of skin friction in turbulent flow due to additives. By studying the effect of polymers on these coherent states, we hope to gain a better understanding of the mechanisms responsible for drag reduction.
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