The drag of turbulent flows can be drastically decreased by adding small amounts of high molecular weight polymers. While drag reduction initially increases with polymer concentration, it eventually saturates to what is known as the maximum drag reduction (MDR) asymptote; this asymptote is generally attributed to the dynamics being reduced to a marginal yet persistent state of subdued turbulent motion. Contrary to this accepted view, we show that, for an appropriate choice of parameters, polymers can reduce the drag beyond the suggested asymptotic limit, eliminating turbulence and giving way to laminar flow. At higher polymer concentrations, however, the laminar state becomes unstable, resulting in a fluctuating flow with the characteristic drag of the MDR asymptote. Our findings indicate that the asymptotic state is hence dynamically disconnected from ordinary turbulence. © 2018 American Physical Society.
Physical Review Letters
The authors thank Philipp Maier and the IST Austria workshop for their dedicated technical support.
Choueiri GH, Lopez Alonso JM, Hof B. Exceeding the asymptotic limit of polymer drag reduction. Physical Review Letters. 2018;120(12). doi:10.1103/PhysRevLett.120.124501
Choueiri, G. H., Lopez Alonso, J. M., & Hof, B. (2018). Exceeding the asymptotic limit of polymer drag reduction. Physical Review Letters. American Physiological Society. https://doi.org/10.1103/PhysRevLett.120.124501
Choueiri, George H, Jose M Lopez Alonso, and Björn Hof. “Exceeding the Asymptotic Limit of Polymer Drag Reduction.” Physical Review Letters. American Physiological Society, 2018. https://doi.org/10.1103/PhysRevLett.120.124501.
G. H. Choueiri, J. M. Lopez Alonso, and B. Hof, “Exceeding the asymptotic limit of polymer drag reduction,” Physical Review Letters, vol. 120, no. 12. American Physiological Society, 2018.
Choueiri GH, Lopez Alonso JM, Hof B. 2018. Exceeding the asymptotic limit of polymer drag reduction. Physical Review Letters. 120(12), 124501.
Choueiri, George H., et al. “Exceeding the Asymptotic Limit of Polymer Drag Reduction.” Physical Review Letters, vol. 120, no. 12, 124501, American Physiological Society, 2018, doi:10.1103/PhysRevLett.120.124501.