The application of nite-dimensional dynamical systems theory to non-Newtonian vortex ow indicates the presence of complex temporal dynamics that is attributed to shear thinning and normal stress (giving rise to the so-called Weissenberg rod climbing phenomenon). These aspects are examined for Rayleigh-Benard thermal convection and Taylor-Couette rotational ow, in an attempt to elucidate on the ...

We report the observation of defects with fractional topological charges (disclinations) in square and hexagonal patterns as numerical solutions of several generic equations describing many pattern-forming systems: Swift-Hohenberg equation, damped Kuramoto-Sivashinsky equation, as well as nonlinear evolution equations describing large-scale Rayleigh-Benard and Marangoni convection in systems wi...

The growth of domains of stripes evolving from random initial conditions is studied in numerical simulations of models of systems far from equilibrium such as Rayleigh-Benard convection. The size of the domains deduced from the inverse width of the Fourier spectrum is found to scale as t 1/5 for both potential and nonpotential models. The morphology of the domains and the defect structures are ...

The linear stability of a horizontal fluid layer, confined between two rigid walls, heated from below and cooled from above is considered. The temperature gradient between the walls consists of a steady part and a periodic part that oscillates with time. Only infinitesimal disturbances are considered. Numerical results for the critical Rayleigh number are obtained for various Prandtl numbers an...

2014 In this article, we report the measurement and analysis of the climbing velocity of an isolated dislocation in a Rayleigh-Bénard roll structure of large extension, as a function of the wavenumber and of the Rayleigh number. The motion of this dislocation in the otherwise regular structure is found to be a wavenumber selection mechanism. Further, we compare this mechanism with that provided...

We have designed and built an apparatus for real-time acoustic imaging of convective flow patterns in optically opaque fluids. This apparatus takes advantage of recent advances in two-dimensional ultrasound transducer array technology; it employs a modified version of a commercially available ultrasound camera, similar to those employed in nondestructive testing of solids. Images of convection ...

Possibility of thermal convection in the form of asymmetric squares in a thin layer of Boussinesq fluids of large lateral extension confined between stress-free and conducting flat boundaries is investigated numerically using a seven mode Lorenz-like model. For fluids with moderate and high Prandtl numbers (4<sigma<20) and in a narrow window of high Rayleigh numbers (12<R/R(c)<15), which depend...

The linear stability of a horizontal layer of fluid heated from below and above is considered. In addition to a steady temperature difference between the walls of the fluid layer, a time-dependent periodic perturbation is applied to the wall temperatures. Only infinitesimal disturbances are considered. Numerical results for the critical Rayleigh number are obtained at various Prandtl numbers an...