Joule heating and buoyancy effects in electro-osmotic peristaltic transport of aqueous nanofluids through a microchannel with complex wave propagation

Electro-osmotic peristaltic transport of aqueous nanofluids in a two-dimensional micro-channel is examined analytically. Such flows arise in bio-mimetic pumping systems at the very small scale of interest in physiological treatment e.g. occular drug delivery systems. Complex waveforms are imposed at the walls to mimic sophisticated peristaltic wave propagation scenarios. Nano-particles are assumed to be in local thermal equilibrium. Joule electro-thermal heating is included. The dimensional conservation equations are linearized and transformed from the wave to the fixed (laboratory) frame under lubrication theory approximations. The emerging dimensionless model features a number of important thermo-physical, electrical and nanoscale parameter, namely thermal and solutal (basic density) Grashof numbers, nanoscale Brownian motion parameter, thermophoresis parameter, Helmholtz-Smoluchowski velocity (maximum electro-osmotic velocity), Debye electrokinetic length and Joule heating to surface heat flux ratio. Closed-form solutions are derived for the nano-particle volume fraction, temperature, axial velocity, averaged volumetric flow rate, pressure difference across one wavelength, skin friction (wall shear stress function), Nusselt number (wall heat transfer rate) and stream function distribution in the wave frame. The influence of selected parameters on these flow variables is studied with the aid of graphs. Bolus formation is also visualized and streamline distributions are observed to be strongly influenced and asymmetric in nature. (C) 2017 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.