ملخص: The present work determines numerically and analyses the dynamic and thermal fields resulting from natural convection in vertical cylinders partially filled with a liquid. The finite difference method has been used to solve the equations governing these flows. Two different types of boundary conditions were implemented in the solution of these equations: in the first case, a temperature which varies sinusoidally on all the boundaries of the cylinder was imposed and, in the second case, a sinusoidal heat flux was imposed. In the case of variable wall temperature, it was noticed that the flow becomes more and more complex and passes from a monocellular structure at the beginning of the period to a multicellular structure at the end of the period, provoked by the differences in temperature that appear within the fluid. Also, despite the imposition of the same temperature on all walls, it was observed that the majority of the heat is exchanged through the vertical wall of the cylinder. In the case of variable wall flux, a nearly constant local heat transfer was predicted for all walls but the mean transfer was larger for the transversal wall. The flow is here monocellular and is little perturbed because of the continuous heating. It was also noted the formation of thermal stratification which is not as quickly destroyed as in the case of prescribed variable wall temperature.AbstractLe present travail a pour but de determiner numeriquement et d'analyser les champs dynamiques et thermiques qui resultent de la convection naturelle dans des cylindres verticaux partiellement remplis de liquide. La methode des differences finies a ete utilisee pour resoudre les equations regissant ces ecoulement. Ces equations etaient sujettes a deux conditions aux limites differentes: dans le premier cas, on a impose une temperature qui varie sinusoidalement sur toutes les parois du cylindre et, dans le second cas, un flux de chaleur sinusoidal. Dans le cas d'une temperature parietale variable, on a remarque que l'ecoulement devient de plus en plus complexe et passe d'une structure monocellulaire, au debut de la periode, a une structure multicellulaire, a la fin de la periode, provoquee par les differences de temperature qui naissent au sein du fluide. Aussi, malgre l'imposition de la meme temperature sur toutes les parois, on a constate que la majorite de la chaleur s'echange a travers la paroi transversale du cylindre. Dans le cas d'un flux parietal variable, on a predit un transfert local de chaleur presque constant a travers les differentes surfaces du cylindre et un transfert moyen superieur a travers la paroi transversale. L'ecoulement est ici monocellulaire et est peu perturbe, car il y a apport de chaleur. On a aussi note la formation d'une stratification thermique, qui n'est pas detruite aussi rapidement que dans le cas d'une temperature parietale variable.

لغة: فرنسية