Numerical study of brownian motion and thermophoresis on free convection in a trapezoidal enclosure using buongiorno s nanofluid model

Abstract

In this thesis, a numerical analysis has been carried out on free convection in a trapezoidal enclosure with sinusoidal temperature distributions on both side walls using Buongiorno’s model. The model takes into account the Brownian motion and thermophoresis effect on the flow, temperature, and concentration fields. Non-uniform temperature and nanoparticle volume fraction distributions have been imposed on both inclined surfaces. Top and bottom parallel surfaces have been kept as adiabatic. All the walls will be considered no slip and impermeable. The governing equations along with above boundary conditions have been initially transformed into non-dimensional form using appropriate similarity transformation and then solved numerically, employing the finite element method of Galerkin’s weighted residual approach. The code validation will be carried out. Nanofluids on the flow structure and heat transfer characteristics will be investigated in details. Results will be presented in terms of streamlines, isothermal lines and iso-concentration lines for different values of governing parameters such as Lewis number (Le), Brownian motion (Nb), Buoyancy ratio (Nr), Prandtl number (Pr), thermophoresis (Nt) and Rayleigh number (Ra). The effect of Brownian motion and thermophoresis on the fluid flow, temperature, and concentration will be identified and finally the flow, heat and concentration controlling parameters for a specific heat and mass transfer application in a trapezium shaped cavity will be obtained. Result demonstrates that, the increase of Brownian motion leads to increase in average Nusselt number by 34.75% and 34.27% for the right and left walls, respectively.