We experimentally study spreading of the Belousov-Zhabotinsky reaction behind a bluff body in a laminar flow. Locations of reacted regions (i.e., regions with high product concentration) correlate with a moderate range of Lagrangian stretching and that range is close to the range of optimal stretching previously observed in topologically different flows [T. D. Nevins and D. H. Kelley, Phys. Rev. Lett. 117, 164502 (2016)]. The previous work found optimal stretching in a closed, vortex dominated flow, but this article uses an open flow and only a small area of appreciable vorticity. We hypothesize that optimal stretching is common in advection-reaction-diffusion systems with an excitation threshold, including excitable and bistable systems, and that the optimal range depends on reaction chemistry and not on flow shape or characteristic speed. Our results may also give insight into plankton blooms behind islands in ocean currents.
Bibliographical noteFunding Information:
The authors gratefully acknowledge I. A. Mohammad, R. S. Russell, and B. F. Knisely for helpful comments and fabrication expertise. The Xerox Engineering Fellows Program at the University of Rochester supported R. O. Colón and partially supported J. Wang. The Discover Grant at the University of Rochester also partially supported J. Wang. T. D. Nevins was supported by the Department of Defense (DoD) through the National Defense Science & Engineering Graduate Fellowship (NDSEG) Program.
© 2017 Author(s).