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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 1519-1532 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The phase equation approach for the description of patterns in a spatially varying environment is tested for realistic setups. To this end the phase equation for axisymmetric Taylor vortex flow with spatially varying cylinder radii (spatial ramps) is derived and solved for various geometries which allow a detailed comparison with recent experiments. The wave number selected by subcritical ramps and its dependence on the geometry is determined. A suitable choice of the ramp allows the selection of wave numbers for which the pattern is unstable with respect to a wavelength changing instability (e.g., Eckhaus instability). This leads to a drift of the pattern. The drift velocity is calculated as a function of the Reynolds number for different geometries. Without any adjustable parameters the results for the selected wave numbers as well as for the drift velocities agree well with recent experiments. The calculations suggest the possibility of spatiotemporal chaos in suitably ramped systems.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 83 (1985), S. 3941-3947 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Within the framework of a reaction-diffusion model we study the influence of active or passive surfaces (e.g., membranes) on extended chemical systems. The surface is described by boundary conditions. Using linear stability analysis we find time-independent boundary conditions which induce oscillatory instabilities of the homogeneous state leading to boundary oscillations. Two cases are of special interest:(i) autocatalysis takes place only in the bulk, whereas coupling occurs only at the surface (or vice versa); (ii) all reactions take place at the surface but bulk diffusion is still essential for the oscillations. Phase diffusion theory and numerical simulation show that for oscillating and excitable (or bistable) bulk systems these boundary conditions can act as a pacemaker leading to phase-locked and quasiperiodic oscillations. The stability of the arising phase waves is discussed. For systems with stationary spatial bulk patterns boundary oscillations can constitute an efficient wavelength selection mechanism.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 59 (1985), S. 245-251 
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Rayleigh-Bénard convection is considered in the presence of a weakly nonuniform temperature distribution and weakly nonuniform layer height with their gradients perpendicular to the (parallel) convection rolls. In the infinite Prandtl number limit the phase equation that describes the slow spatial and temporal evolution of the local wave number is derived. Evaluating the equation near threshold and for stress-free boundary conditions we find nonuniversal wavenumber selection, forced phase diffusion with moving patterns, and other measurable effects.
    Type of Medium: Electronic Resource
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