Fluctuation-Dominated Kinetics under Stirring

R. Reigada,1 F. Sagués,1 I. M. Sokolov,2,3 J. M. Sancho,4 and A. Blumen2 1Departament de Quı́mica Fı́sica, Universitat de Barcelona, Diagonal 647, Barcelona 08028, Spain 2Theoretische Polymerphysik, Universität Freiburg, Rheinstrasse 12, D-79104 Freiburg i. Br., Germany 3P. N. Lebedev Physical Institute of the Academy of Sciences of Russia, Leninski Prospect 53, Moscow 117924, Russia 4Departament d’Estructura i Constituents de la Matèria, Universitat de Barcelona, Diagonal 647, Barcelona 08028, Spain (Received 9 May 1996) We investigate the effects of stirring on the kinetics of the A 1 B ! 0 reaction under stoichiometrical conditions in 2D. We consider both a steady eddy-lattice flow and a random flow mimicking turbulence. In both situations complex decay patterns are detected. Only an intermediate stage of the reaction is dominated by mixing. The long-time behavior shows fluctuation-dominated kinetics, cstd ~ t21y2, governed by effective diffusion. For the case of an eddy-lattice flow a very slow intermediate regime emerges, cstd ~ t21y4, which is associated with the closed topology of flow lines. [S0031-9007(96)02254-5]