Polymer-induced drag enhancement in turbulent Taylor-Couette flows: direct numerical simulations and mechanistic insight.
We report for the first time the polymer-induced breakdown of large-scale Taylor vortex structures leading to drag enhancement in viscoelastic turbulent Taylor-Couette flows. Specifically, we demonstrate that upon the addition of trace amounts of soluble high molecular weight macromolecules the Newtonian large-scale Taylor vortices are replaced by small-scale vortices in the inner and outer cylinder wall regions. This flow transition and a commensurate drag increase of up to 62% are facilitated by the presence of large polymeric normal stresses in a narrow region immediately close to the outer wall. A simple mechanism for this striking flow transition is proposed with the aim of paving the way for a mechanistic understanding of polymer-induced structure and drag modifications in high-Re turbulent curvilinear flows.
Department of Chemical and Biomolecular Engineering, Materials Research and Innovation Laboratory, University of Tennessee, Knoxville, Tennessee 37996-2200, USA and Department of Modern Mechanics, University of Science and Technology of China, Anhui, Hefei 230026, China.
Nansheng
N
Liu
Bamin
B
Khomami