SPIRAL DYNAMICS IN PATTERN-FORMING SYSTEMS - MEAN-FLOW EFFECTS

Mean-flow effects are discussed for two different pattern-forming syst ems: Rayleigh-Benard convection and Faraday instability in viscous flu id. In both systems spirals are observed in certain parameter regions. In the Rayleigh-Benard convection, the spiral-core instability is sho wn to occur due to the mean flow generated by the curved rolls near th e core. In the Faraday instability, the mean how which is generated by rapidly decaying surface waves near the wall, causes wave number frus tration which leads to a rigid-body spiral rotation. In both cases we use phenomenological Swift-Hohenberg-type equations for the order para meter coupled to a large-scale mean flow. Numerical simulations are co mpared to recently reported experimental results. (C) 1998 Published b y Elsevier Science B.V. All rights reserved.