Showing papers on "Boussinesq approximation (buoyancy) published in 1983"

Effects of Variable Physical Properties on Free Convection in a Porous Insulating Layer

Abstract: A numerical study is made of the effects of variable properties on free convection in vertical, 'herium-(or air-) saturated porous layer. The temperature differences between hot and cold boundary walls are as large as 1000°C. The effects of variations in viscosity, thermal conductivity and density are included. Flow patterns are found to be considerably distorted in a horizontal direction to the symmetrical patterns predicted by the constant-property theory, whereas the overall heat-transfer characteristics do not alter very much provided that representative properties are evaluated at a mean temperature. At sufficiently large amplitude of convection, however, the deviation from the Boussinesq approximation is not negligible.

Comparison between anelastic and Boussinesq approximation for cumulus convection

Abstract: Solutions of the anelastic pressure equation are studied, with a perturbative scheme, for certain assumed and idealized forcing distributions. Previous results, obtained in the Boussinesq approximation and the new ones are compared for the case of deep cumulus convection. Meaningful differences are found in the upper and lower parts of the cloud between the new and the previous estimate of vertical pressure gradient force induced by buoyancy forcing and by drag forcing in the case of a nonprecipitating cloud.

The combined influence on the transition of the rounding of the tip and the higher temperature of the nose of the model could be responsible for the change in the transi- tion Reynolds number when the pressure in the ballistic experiments is changed.

Abstract: interacting fluids. The model admits an increasing concentration of the solid particles with the height, which leads to circulatory flows. Approximate equations of motion of the liquid and the solid particles are obtained, and these are analogous to the Boussinesq approximation in the case of natural convection in a pure liquid. The equations contain a parameter which is analogous to the Rayleigh number and characterizes the stability of the layer. An approximate analytic solution to the corresponding eigenvalue problem is found. The spectrum of Rayleigh numbers and the sizes of the convective cells are determined. The obtained results provide an explanation for the existence of the multicenter circulatory motions of the phases frequently observed in a fluidized beds and make it possible to determine the sizes of the circulatory regions. Information about the Rayleigh number spectrum and the sizes of the regions is needed to solve the problem of the scale transition and also to enable the choice of measures to suppress or intensify the displacement processes. The experimental data of [i, 2] (see also [3]) show that there can be a distribution of the concentration of the solid particles in a homogeneous fluidized bed in which the total density of the two-phase medium increases with the height, this being especially characteristic when the densities of the liquid and the solid particles are comparable.