Numerical study on the combined effects of Brownian motion and thermophoresis on an unsteady magnetohydrodynamics nanofluid boundary layer flow

Buongiorno’s two-phase model is adopted to study the impacts of the thermophoresis effect and Brownian motion on an unsteady nanofluid flow through an irregular channel due to a stretching sheet in the presence of magnetic field. The copper oxide nanoparticles are dispersed in the base solution (i.e., water) and the nanofluid thus developed is considered as an operating fluid. The thermophysical properties such as density, thermal conductivity, viscosity, heat capacitance and thermal expansion of the considered nanofluid are determined using established laws and mixture theory. The flow and heat transfer are described by the boundary layer equations that correspond to the flow field, temperature, and concentration, and associated boundary conditions are solved numerically by employing an effective and optimized finite difference technique. The convergence criteria of the developed numerical algorithm for the obtained solutions are verified. The significant features of momentum, temperature, and concentration distributions are due to the influence of key parameters which are of physical interest such as magnetic parameter, the amplitude of a wavy channel, particle–density increment parameter, Brownian diffusion coefficient, nanoparticle Lewis number are analyzed in detail.