The addition of a small amount of a long chain, high-molecular weight polymer to the turbulent flow of a Newtonian fluid causes drag-reduction. The mechanism for this phenomena is not well understood. Pulsed image velocimetry was used to capture the structure of turbulent flow of water and a polymer solution in planes parallel and perpendicular to the top wall of a channel. A 40% drag reduction was obtained with a 3.5 ppm polymer solution. The two flow fields at the center plane were quite similar. However, at a plane close to the wall, long, stream wise, streaks of low and high momentum flow were observed in the polymer solution, the low speed streaks being more prominent. These streaky structures did not appear in the flow field of water at the same physical location. This seems to suggest that the streamwise vortices are enlarged as a result of addition of polymers.
|Original language||English (US)|
|Title of host publication||American Society of Mechanical Engineers, Fluids Engineering Division (Publication) FED|
|Number of pages||3|
|State||Published - 1996|
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