Numerical simulation of thermal convection of Giesekus fluid in a square cavity with the elliptical column

Abstract

The convection heat transfer of a viscoelastic Giesekus fluid between a square cavity and a heated inner elliptical column is considered by the open source software OpenFOAM. When the Prandtl number is 7, physical parameters, such as Rayleigh number (103≤Ra≤107), the long semiaxis of the inner elliptical column (0.2H≤a≤0.4H), Weissenberg number (1≤Wi≤100), mobility factor (0≤α≤0.5), and the polymer viscosity ratio (0.1≤β≤0.9), are investigated. These combined effects are discussed using streamlines, thermal field distributions, and average Nusselt numbers. The numerical results are validated by the comparison with other numerical and experimental ones. The high Rayleigh number destroys the symmetry of the streamlines of the Giesekus fluid, which is a phenomenon not present in Newtonian fluids. At the same time, the high Rayleigh number enhances the flow and heat transfer while exacerbating the instability, leading to periodic oscillations in both flow and heat transfer. The variations of multi-physics fields are analyzed for the cases such as strong elasticity without shear thinning, medium elasticity with medium shear thinning, and weak elasticity with strong shear thinning effects. Stronger elasticity favors the enhancement of flow and heat transfer in viscoelastic fluids, and this effect is more significant when the Weissenberg number is small.