This study examines the impact of dilute polymer solutions on the unique isolated secondary flows between concentric, rotating cylinders, namely Taylor-Couette (TC) flow. We mapped the stability of flow states using Newtonian and dilute polyethylene oxide (PEO) solutions over the Reynolds number range of - 100 Reo 500 and 0 Rei O(103), where subscripts o' and i' refer to outer and inner cylinders, respectively. Elasticity number (El) of the PEO fluids, defined as the ratio of elastic to inertial forces, ranges from O(10- 4) to O(10- 2). This work expands on previous studies by (a) significantly expanding the range of Rei, Reo, and El examined, (b) use of a consistent, conservative protocol for reaching flow states, and (c) rheological characterization of the solutions via shear and capillary breakup extensional rheometry. Using spectral analysis of flow visualization of the r-z or z- planes, we find the effect of El on the critical conditions for laminar and chaotic axisymmetric and nonaxisymmetric flow states is nonmonotonic and mode-dependent, with greater modification of higher order transitions involving small-scale features. While the critical conditions are modified by low El for all transitions, the flow states vary from those for Newtonian fluids at higher Rei and for the more elastic fluids.
Bibliographical noteFunding Information:
The authors are grateful for the support of the National Science Foundation through Grant No. CTS-0335169. Throughout the course of this work, C.S.D. held a National Science Foundation Graduate Research Fellowship and an American Association of University Women Selected Professions Engineering Dissertation Fellowship. S.J.M. gratefully acknowledges support from the Radcliffe Institute for Advanced Study during the preparation of this manuscript. The authors are also grateful to Malvern Instruments for the loan of the Malvern Gemini rheometer.
- Dilute polymer solutions
- Fluid dynamics
- High velocity flows
- Polyethylene oxide