Drag Reduction in Turbulent Flows Due to Polymer Additives
Abstract
A theory of drag reduction in turbulent flows by polymer additives is presented. It has long been known that adding modest concentrations of polymer additives to turbulent pipe flows can result in significant reduction in drag. Here, drag reduction occurs due to the formation of a momentum transport barrier, signified by velocity profile steepening in the inertial sublayer. It is interesting to note that while momentum transport decreases, turbulence intensities are essentially unchanged. We develop a theory using coupled fluid equations for the fluid velocity field and the polymer elasticity field. This model has many similarities to MHD, and supports elastic waves similar to Alfven waves. The elastic/Alfvenic character of the turbulence naturally leads to energy equipartition and thus results in cancellation of Reynolds and elastic stresses over the range where the polymer is activated, thus quenching momentum transport in a part of the inertial sublayer. This topic is relevant to plasma physics in that this problem has many similarities to transport barrier and MHD turbulence physics.
- Publication:
-
APS Division of Plasma Physics Meeting Abstracts
- Pub Date:
- November 1999
- Bibcode:
- 1999APS..DPP.UP190D