Periodic mixed convection of a nanofluid in a cavity with top lid sinusoidal motion

Abstract

The periodic mixed convection of a water–copper nanofluid inside a rectangular cavity with aspect ratio of 3 is investigated numerically. The temperature of the bottom wall of the cavity is assumed greater than the temperature of the top lid which oscillates horizontally with the velocity defined as u =  u0 sin ( ωt). The effects of Richardson number, Ri, and volume fraction of nanoparticles on the flow and thermal behaviour of the nanofluid are investigated. Velocity, temperature profiles, and streamlines are presented. It is observed that when Ri < 1, heat transfer rate is much greater than when Ri > 1. The higher value of Ri corresponds to a lower value of the amplitude of the oscillation of Nu m in the steady periodic state. Moreover, increasing the volume fraction of the nanoparticles increases the heat transfer rate.