Numerical study of effect of uniform sinusoidal roughness elements on nanofluid natural convection, using lattice Boltzmann method

In this paper, the effect of uniform sinusoidal roughness elements on natural convection heat transfer of nanofluids within an enclosed cavity is studied by adopting the lattice Boltzmann Model. The uniform sinusoidal roughness elements are presented on the vertical walls, while the Right and left walls are kept at hot and cold constant temperatures, respectively. The variation of density is slight thus; hydrodynamics and thermal fields equations are coupled using the Boussinesq approximation. Effective viscosity and thermal conductivity of nanofluid are obtained using KKL model implementing Brownian motion of nanoparticles. The velocity and temperature distribution are both solved by D2Q9 scheme by using a Fortran code. The study have been carried out for Rayleigh number, location of roughness elements, frequency of roughness elements, dimensionless amplitude of uniform sinusoidal roughness elements and various volume fractions of Al2O3 nanoparticles in the base water fluid. Results show that the heat transfer increases with the increment of Rayleigh number and nanoparticles volume fractions, but Nusselt number decreases by the increment of the frequency of roughness elements and dimensionless amplitude of uniform sinusoidal roughness elements. The rate of increase or decrease of Nusselt number is a function of roughness elements locations.