Natural convection of nanofluids in a wavy porous cavity

Abstract

In this piece of work, a numerical investigation of natural convection is carried out on the buoyancy-driven flow of nanofluids and heat transfer through porous media packed inside a wavy cavity. The cavity is placed horizontal, and its right vertical wall is of wavy nature, the bottom and top walls of the cavity are adiabatic, and there is a temperature difference between the left and right vertical wall. The dimensionless governing equations for the flow of nanofluids through the Darcian porous media are solved iteratively by using finite difference method. The study is conducted for wide range of governing parameters, such as Rayleigh-Darcy number $(Ra=10,{10}^2,{10}^3)$ , nanoparticle volume fraction $(\varphi =0\%,5\%,10\%,15\%,20\%)$ for three types of nanofluids $(A{l}_2{O}_3$ - $H_{2}O$ , Cu- $H_{2}O$ , TiO₂- $H_{2}O)$ , the waviness of the vertical wall controlled by dimensionless length of amplitude of the wave $(a=0.05,0.15,0.25)$ and number of undulations per unit length (N = 1, 3, 5). The simulated results reveals that the presence of nanoparticles enhances the convective heat transfer process at low Ra, and the wall affects the local convection rate and it also controls the overall heat transfer rate. For a cavity with N = 3, $\overline{Nu}$ is increased by about 68% at Ra = 10, and at $Ra={10}^3$ the increment is about 11% as the a is increased from 0.05 to 0.25 having 20% of nanoparticles volume friction.