Polymer-induced flow relaminarization and drag enhancement in spanwise-rotating plane Couette flow. (25th December 2020)

• Record Type: Journal Article
• Authors: Zhu, Yabiao; Song, Jiaxing; Liu, Nansheng; Lu, Xiyun; Khomami, Bamin
• Is Part Of: Journal of fluid mechanics. Volume 905(2020)
• Publication Date: 2020-12-25
• Subjects: viscoelasticity, -- rotating turbulence; Fluid mechanics -- Periodicals; 532.005
• DOI: 10.1017/jfm.2020.752
• Languages: English
• ISSNs: 0022-1120

Abstract

Abstract: Abstract : Direct numerical simulation of polymer-induced flow relaminarization of turbulent spanwise-rotating plane Couette flow (RPCF) is reported for the first time. Specifically, the reverse transition pathway from a Newtonian turbulent RPCF to a fully relaminarized drag enhanced viscoelastic flow has been elucidated. Evidently, this transition occurs gradually by weakening and eventual elimination of small-scale vortices as the Weissenberg number ( $Wi$ ) is enhanced, paving the way for a two-dimensional laminar flow consisting of large-scale and highly organized roll cells. The influence of polymer additives on convective momentum exchange by large-scale roll cells and small-scale turbulent vortices, namely, the drag reduction (DR) realized by elimination of turbulent vortices and the significant drag enhancement (DE) that results from polymer roll cell interactions has been identified as the mechanism of DE. The observed vortical changes point to a universal mechanism for the coupling of polymer chains and turbulent vortices in wall-bounded viscoelastic DE and DR flows.