title: Involutes: the geometry of chemical waves rotating in annular membranes.
abstract: According to earlier theories certain parts of a chemical wave front propagating in a 2-D excitable medium with a convex obstacle should be involutes of that obstacle. The present paper discusses a special case where self-sustained chemical waves are rotating around a central obstacle in an annular 2-D excitable region. A simple geometrical model of wave propagation based on the Fermat principle (minimum propagation time) is suggested. Applying this model it is shown that the wave fronts in the case of an annular excitable region should be purely involutes of the central obstacle in the asymptotic state. This theory is supported by experiments in a novel membrane reactor where a catalyst of the Belousov-Zhabotinsky reaction is fixed on a porous membrane combined with a gel medium. Involutes of circular and triangular obstacles are observed experimentally. Deviations from the ideal involute geometry are explained by inhomogeneities in the membrane. (c) 1995 American Institute of Physics.
authors.affiliation: Center for Complex and Nonlinear Systems and the Department of Chemical Physics, Technical University of Budapest, H-1521 Budapest, HungaryFachbereich Physikalische Chemie, Philipps Universitat Marburg, D-35032 Marburg/Lahn, Germany.
authors.forename: Attila
authors.initials: A
authors.lastname: Lazar
authors.forename: Zoltan
authors.initials: Z
authors.lastname: Noszticzius
authors.forename: Henrik
authors.initials: H
authors.lastname: Farkas
authors.forename: Horst-Dieter
authors.initials: HD
authors.lastname: Forsterling