Rotating spirals in a Faraday experiment.

We report experiments and model simulations of patterns of parametrically excited capillary ripples in a large aspect-ratio cell with thin horizontal layer of viscous fluid subjected to sinusoidal vertical oscillations. We found stable rotating spirals with different topological charges in the parameter range where steady straight rolls were observed previously. Formation of multiarmed spirals via dislocations approaching a target core was observed. The direction of the spiral rotation depends on its chirality and is always consistent with wave propagation towards the core. Wave drift towards the spiral core is associated with the shear flow which is generated near the walls by rapidly decaying viscous surface waves. @S1063-651X~96!02911-X#