Natural convection analysis of copper–alumina/water hybrid nanofluids in a U-shaped cavity with adiabatic wavy walls

Abstract

ABSTRACT The numerical analysis of natural convection heat transfer of copper–alumina hybrid nanofluid inside a U-shaped enclosure with adiabatic wavy walls is presented in this manuscript. The Boussinesq approximation is employed in the governing equation of the model. Dimensionless variables are used to transform the governing equation into a dimensionless form. The domain is discretized into a finite number of three-node triangular elements. The weighted residual Galerkin finite element method is used to solve the model numerically. To ensure numerical stability, a damped Newton–Raphson algorithm is employed after each finite element iteration. The analysis of the influence of the nanoparticle volume fraction of 0–0.1, nanoparticle ratio of copper: alumina from 0:1 to 1:0, the Rayleigh number from to , and the amplitude and undulation of the wavy walls of 0.05−0.15 and 1−5 respectively are extensively discussed in this paper. The streamlines, isotherms, and vorticity distribution along with the average and local Nusselt number to investigate the effect of various parameters on the fluid flow and heat transfer. It is observed that the hybrid nanofluid increases the thermal performance within the wavy U-shaped cavity by 7% and 12% for one and two adiabatic wavy walls correspondingly compared to its mono nanofluid components and pure water.