Natural convection of Cu-water nanofluid in enclosed cavity with porous effect and wavy surface based on energy-flux-vector visualization method

Abstract

This paper studies the influences of a porous medium and wavy surface on natural convection of Cu-water nanofluid in an enclosed cavity based on the energy-flux-vector method. The effects of the Darcy number (Da), Rayleigh number (Ra), porosity (ε), nanoparticle volume fraction (ϕ), and geometric wave amplitude (αw) on the energy flux vectors, isotherms, mean Nusselt number (Num), total entropy generation (St), and Bejan number (Be) are examined. It indicates that given a low Ra and any value of the Da or a high Ra and a low Da, the energy flux vectors, isotherms, and entropy generation have similar distributions. Under such conditions, St and Num have low values, while Be approaches unity. However, if Ra and Da have high values, the energy flux vectors form flow recirculation structures. Therefore, St and Num increase, while Be decreases. As ε increases, St and Num increase, while Be reduces. Finally, when a high Ra with a high Da is given, all Num, St, and Be increase as αw is increased.