Thermogravitational and Thermocapillary Convection in a Fluid Layer

Preliminary remarks. In the preceding chapters it was assumed that the fluid velocity field is independent of the temperature and concentration distributions. However, there are a few phenomena in which the influence of these factors on the hydrodynamics is critical. This influence arises from the fact that various physical parameters of fluids, such as density, surface tension, etc. are temperature or concentration dependent. 

For example, the convective motion of a liquid in a vessel whose opposite walls are maintained at different temperatures is due to the fact that the fluid density is normally a decreasing function of temperature. The lighter liquid near the heated wall tends to rise, whereas the heavier liquid near the opposite wall tends to lower. This is one of the examples in which the so-called gravitational (in this case, thermogravitational) convection manifests itself. 

If the surface tension coefficient is not constant along the interface between two nonmixing fluids, then there arise additional tangential stresses on the interface they are referred to as capillary stresses and can substantially affect the motion of the fluid or even solely determine it in the absence of gravitational and 

The intense study of numerous problems related to the temperature or concentration gradient influence on the fluid motion is stimulated, apart from purely scientific interest, by a possibility of their wide applications in technology (first of all, chemical and space technology). 

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