Numerical Study of Effect of Polymer Additives on Heat Transport in Turbulent Rayleigh- Bénard Convection

Abstract

In this study, the Reynolds-Averaged-Navier-Stokes (RANS) model combined with the Cross Viscosity Equation is used, applied to the soft turbulence regime (Ra =5×105~4×107) and hard turbulence regime (Ra>4×107) of Rayleigh-Bénard convection (RBC). The relation curves between heat transport (Nusselt number) and other parameters, as well as flow pattern changes of RBC are obtained for the cases with different Rayleigh number and concentration of the polymer additive. The simulations show that the presence of polymer additive can lead to an enhancement of the heat transfer with larger effect in the hard turbulence regime than those in the soft turbulence regime. It is also shown that in the soft turbulence regime the reversal cycles are shorter than in hard turbulence regime. The symmetric vortices in the diagonal corner of enclosed space shrink and the velocities of large-scale circulation (LSC) increase accordingly.

Heat transfer enhancement and reduction in low-Rayleigh number natural convection flow with polymer additives

“…For polymer parameters, the viscosity ratio β is kept constant, β = 0.9, matching previous viscoelastic channel flow simulations performed in previous studies 19,20,22 . The parameter space under investigation is a matrix (L,Wi) with L = (10, 25, 50, 100) and Wi = (1,5,10,15,20,25,30,35,40,45), with a few additional simulations for L = 15, 20, 30, 40 at Wi = 10 and L = 25, 40 at Wi = 40.…”

“…Cheng et al 10 showed in two-dimensional RBC simulations that the amount of HTR behaves non-monotonically with the Weissenberg number. They related this non-monotone behavior to modifications of the period of the large scale circulation and boundary layer thickness.…”