Manfred Lücke

Convection Structures of Binary Fluid Mixtures in Porous Media

Matthias Albert Augustin, Rudolf Umla, Manfred Lücke

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Convection Structures of Binary Fluid Mixtures in Porous Media

Matthias Albert Augustin, Rudolf Umla, Manfred Lücke

de, gb (code pays fourni par la source)

Elongational flow effects on the vortex growth out of Couette flow in ferrofluids

Sebastian Andreas Altmeyer, Andreas Leschhorn, Ch. Hoffmann, Manfred Lücke

The growth behavior of stationary axisymmetric vortices and of oscillatory, nonaxisymmetric spiral vortices in Taylor-Couette flow of a ferrofluid in between differentially rotating cylinders is analyzed using a numerical linear stability analysis. The investigation is done as a function of the inner …

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Convection Structures of Binary Fluid Mixtures in Porous Media

Matthias Albert Augustin, Rudolf Umla, Manfred Lücke

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Viscoelastic convection: Few-modes model and numerical simulations of field equations for Maxwellian fluids

Marco Salm, Manfred Lücke

The structure formation of convection rolls in Maxwellian fluids that are heated from below in a Rayleigh-Bénard setup is investigated close to onset with a simple few-modes ansatz and by solving the hydrodynamic field equations with a finite-difference method. Depending on the …

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Collisions of localized convection structures in binary fluid mixtures

A. V. Taraut, Boris L. Smorodin, Manfred Lücke

Collisions of a localized traveling wave structure with a localized stationary structure are investigated. In ethanol–water mixtures with appropriately chosen negative separation ratios, both exist bistably in the unstable quiescent surrounding for a range of supercritical heating rates. Depending on the Rayleigh …

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Three-dimensional convection of binary mixtures in porous media

Rudolf Umla, Matthias Albert Augustin, Björn Huke, Manfred Lücke

We investigate convection patterns of binary mixtures with a positive separation ratio in porous media. As setup, we choose the Rayleigh-Bénard system of a fluid layer heated from below. Results are obtained by a multimode Galerkin method. Using this method, we compute …

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Islands of instability for growth of spiral vortices in the Taylor-Couette system with and without axial through flow

Sebastian Andreas Altmeyer, Ch. Hoffmann, Manfred Lücke

We present numerical calculations of the linearized Navier-Stokes equations for axially extended and axially localized spiral structures in the Taylor-Couette system. The eigenvalue surface for spiral vortices with azimuthal wave number M=2 shows significantly more structure than that for vortices with M=0 …

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Stationary and oscillatory convection of binary fluids in a porous medium

Matthias Albert Augustin, Rudolf Umla, Björn Huke, Manfred Lücke

We investigate numerically stationary convection and traveling wave structures of binary fluid mixtures with negative separation ratio in the Rayleigh-Bénard system filled with a porous medium. The bifurcation behavior of these roll structures is elucidated as well as the properties of the …

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Influence of homogeneous magnetic fields on the flow of a ferrofluid in the Taylor-Couette system

Sebastian Andreas Altmeyer, Ch. Hoffmann, Andreas Leschhorn, Manfred Lücke

We investigate numerically the influence of a homogeneous magnetic field on a ferrofluid in the gap between two concentric, independently rotating cylinders. The full Navier-Stokes equations are solved with a combination of a finite difference method and a Galerkin method. Structure, dynamics, …

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Binary-fluid-mixture convection with low-frequency modulated heating

Boris L. Smorodin, Manfred Lücke

The response behavior of binary fluid convection to low-frequency temporal modulation of the heating is studied for the case of a negative Soret coupling between temperature and concentration gradients. Numerical simulations using a finite difference method are carried out for ethanol-water mixtures …

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End wall effects on the transitions between Taylor vortices and spiral vortices

Sebastian Andreas Altmeyer, Ch. Hoffmann, M. Heise, Jan Abshagen et autres

We present numerical simulations as well as experimental results concerning transitions between Taylor vortices and spiral vortices in the Taylor-Couette system with rigid, nonrotating lids at the cylinder ends. These transitions are performed by wavy structures appearing via a secondary bifurcation out …

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