Modulation of double-diffusive convection during high Rayleigh number flows

In this paper, fully developed turbulent flow induced by thermal and solutal buoyancy forces is numerically studied using the no-turbulence model hybrid lattice Boltzmann scheme. To study high Rayleigh number ( Ra ) cases, the high order regularization along with the fourth order Runge-Kutta scheme were implemented for lattice Boltzmann and energy equations, respectively. A MATLAB code with GPU acceleration was developed and carefully validated against DNS data of other researchers. The effect of the buoyancy ratio ( N ) on heat and mass transfer patterns was studied at Ra = 10 10 and Ra = 10 11 while the Lewis and Prandtl numbers were fixed at 2 and 0.71, respectively. It was found that the buoyancy ratio can be used as a modulation factor to enhance the heat and mass transfer rate, shape the thermal and solutal plumes and reduce turbulence intensity. The time-averaged mean Nusselt number in a range of 10 10 ≤ Ra ≤ 10 11 is increased by around 89%, 108% and 180% when N = − 1 , N = 1 and N = 2 , respectively. On the contrary, the time-averaged mean Sherwood number is incremented by 85%, 115% and 158% under the same N and Ra range conditions.