356 research outputs found

    Thermal convection in a nonlinear non-Newtonian magnetic fluid

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    We report theoretical and numerical results on thermal convection of a magnetic fluid in a viscoelastic carrier liquid. The viscoelastic properties are described by a general nonlinear viscoelastic model that contains as special cases the standard phenomenological constitutive equations for the stress tensor. In order to explore numerically the system we perform a truncated Galerkin expansion obtaining a generalized Lorenz system with ten modes. We find numerically that the system has stationary, periodic and chaotic regimes. We establish phase diagrams to identify the different dynamical regimes as a function of the Rayleigh number and the viscoelastic material parameters

    General Nonlinear 2-Fluid Hydrodynamics of Complex Fluids and Soft Matter

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    We discuss general 2-fluid hydrodynamic equations for complex fluids, where one kind is a simple Newtonian fluid, while the other is either liquid-crystalline or polymeric/elastomeric, thus being applicable to lyotropic liquid crystals, polymer solutions, and swollen elastomers. The procedure can easily be generalized to other complex fluid solutions. Special emphasis is laid on such nonlinearities that originate from the 2-fluid description, like the transport part of the total time derivatives. It is shown that the proper velocities, with which the hydrodynamic quantities are convected, cannot be chosen at will, since there are subtle relations among them. Within allowed combinations the convective velocities are generally material dependent. The so-called stress division problem, i.e. how the nematic or elastic stresses are distributed between the two fluids, is shown to depend partially on the choice of the convected velocities, but is otherwise also material dependent. A set of reasonably simplified equations is given as well as a linearized version of an effective concentration dynamics that may be used for comparison with experiments

    Macroscopic two-fluid effects in magnetorheological fluids

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    Two-fluid model for a fluid with tetrahedral-octupolar order

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    A two-fluid model for the formation of clusters close to a continuous or almost continuous transition

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    A two-fluid model for the macroscopic behavior of polar nematic fluids and gels in a nonchiral or a chiral solvent

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    Ferromagnetic nematics: A macroscopic two-fluid description

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    Two-fluid model for the breakdown of flow alignment in nematic liquid crystals

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    A Two-Fluid Model for the Macroscopic Behavior of Nematic Fluids and Gels in a Chiral Solvent

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