This study examined numerically the natural convection in square cavity filled with (Al2O3- NaK) incompressible nanofluids , with the left wall is kept at high temperature while the right wall is kept at lower temperature. Meanwhile the other two walls are adiabatic. The problem of natural convection is solved by applying Boussinesq assumption. A Double distribution function thermal lattice Boltzmann method with a two relaxation time (TRT) lattice Boltzmann method are used for solving the velocity field by using D2Q9 model ,while a single relaxation time (SRT) lattice Boltzmann method is used for solving the temperature field by using D2Q5 model. Simulation was done by studying the hydrodynamic structure of the flow and its thermal behavior for different Rayleigh numbers and different nanoparticles volume fraction. There is an increase in the heat transfer rate by increasing the nanoparticle volume fraction. There is no effect of nanoparticles volume fraction on the streamlines at Ra =1000, the biggest effect on stream lines by nanoparticles volume fraction exists when Ra =100000 due to the dominance of convection. But there is a change in the isotherms lines when increasing nanoparticles volume fraction for different Rayleigh numbers. There is an increase in the average Nusselt number by increasing nanoparticles volume fraction, which would be more effective at high Rayleigh numbers due to the dominance of convection on the heat transfer mechanism. |
