Simulation of Natural Convection in Diamond Shaped Cavity Filled with Air or Water

Abstract

In the present study, the occurrence and intensity of natural convection in air or water filled as medium in a diamond shape cavity is evaluated as a function of Grashof number. Grashof number represents the buoyancy force effect which leads to the natural convection or circulations inside the cavity. In the context of granular material, diamond shaped cavities or voids are present between the granules. Depending on the shape of granules, the voids also can have various types of boundary shapes. For simulation purpose, a two dimensional diamond shaped cavity is chosen (a square turned 45°). The left and right boundary temperatures are assigned different values corresponding to side wall heating. The gravity direction is considered as four possibilities: positive y-direction, negative y-direction, positive x-direction and negative x-direction representing various configurations of wall heating. These situations correspond to earth’s gravity or centrifugal acceleration. The walls of the cavity are maintained at a temperature difference of 10 °C. The size of the cavity is varied and the maximum velocity magnitude in circulations is obtained for different directions of the gravity using COMSOL Multiphysics. The results of velocity field or circulations are graphically represented and analyzed as a function of Grashof number. It was found from simulation results that the intensity of natural convection is highest for gravity in vertical direction and for air as compared to water.