Double-diffusive natural convection of non-Newtonian nanofluid considering thermal dispersion of nanoparticles in a vertical wavy enclosure

The flow field, thermal field, and solutal field exposed to thermal and solutal buoyancy forces have been investigated in detail within a wavy enclosure filled with copper(Cu)-water nanofluid incorporating the non-Newtonian characteristics predicted by the power-law viscosity model. During the convection process, the random motion of ultrafine Cu-nanoparticles causing an enhanced energy exchange rate is determined using the thermal dispersion model. The governing equations in a dimensionless form are numerically solved utilizing the finite volume method incorporated with the semi-implicit method for pressure linked equations-revised algorithm. The simulations are carried out with different pertinent parameters, such as the Rayleigh number, Lewis number, power-law index, volume fraction, and buoyancy ratio. The effect of the above parameters on the local Nusselt number (Nu) and the local Sherwood number (Sh) is analyzed to understand the heat and mass transfer properties from the heated wavy surface. Results show that the heat transfer rate from the wavy surface declines, but the mass transfer rate gets stronger with growing Lewis number. Both the heat and mass transfer rates become optimum when the nanofluid behaves as a shear thinning fluid. The distribution of Nu and Sh is found to be periodically attenuated from the lower end to the upper end along the hot wavy surface. The distribution of Nu and Sh is observed to be locally maximum at the crest point of the wavy surface. New correlations to predict the average heat and mass transfer rate concerning the studied parameters are proposed with remarkable accuracy. (c) 2021 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).