Slavcho Slavtchev

Technical Note Marangoni instability of a layer of binary liquid in the presence of nonlinear Soret effect

Abstract Although the Soret effect induces only small chemical separations, its influence on the variations of physical parameters may be larger than the influence of the thermal gradient from which it results. The effect has been recognized and extensively studied in the Rayleigh–Benard problem for instabilities generated by density fluctuations 1 , 2 , 3 , 4 . In the same way that for the mixture density, the Soret effect may influence significantly the surface tension variations in the presence of a temperature gradient. The interaction between thermocapillary and concentration-capillary mechanisms for promoting motion in binary mixture fluids has motivated many authors to study the Marangoni–Benard instability in the presence of the Soret effect and important similarities with the Rayleigh–Benard convection have been evidenced [5] .

Steady flows of a laterally heated ferrofluid layer: Influence of inclined strong magnetic field and gravity level

A horizontal ferrofluid layer is submitted to a lateral heating and to a strong oblique magnetic field. The problem, combining the momentum and heat balance equations with the Maxwell equations, introduces two Rayleigh numbers, Ra the gravitational one and Ram the magnetic one, to represent the buoyancy and the Kelvin forces, which induce motion, versus the momentum viscous diffusion and heat diffusion. Whatever the inclination of the magnetic field, the steady solution of the problem is presented as a power series of a small parameter ϵH measuring the ratio of variation of the magnetization across the layer divided by the magnitude of the external imposed field. For cases of physical relevance, comparisons between analytical and numerical studies have lead to a major statement: in the strong field region (ϵH≪1) the zero order solution is the product of the Birikh solution that corresponds to the usual Newtonian fluid submitted to a lateral gradient, multiplied by a modulating factor accounting for inclin...

Gravity level influence on a laterally heated ferrofluid submitted to an oblique strong magnetic field

Summary A horizontal ferrofluid layer is submitted to a lateral heating and to a strong oblique magnetic field. For a thin enough layer, the steady state solution is the product of the classical solution corresponding to the usual Newtonian fluid submitted to a lateral gradient of temperature, times a modulating factor. This last accounts for the inclination and for the ratio Ram/Ra, where Ra is the Rayleigh number due to buoyancy and Ram the magnetic Rayleigh number due to the Kelvin magnetic forces. Physically, fundamental modifications of the temperature and velocity profile intervene when Ram/Ra >> 1, since, as function of the inclination of the magnetic field, the direction of motion in the infinitely elongated cells can become inverted.