The study of electroosmotic flow of biorheological fluids has been employed in the advancement of diversified biomicrofluidics systems. To explore more in this field, a mathematical model is developed to investigate the electroosmotic flow of pseudoplastic aqueous nanoliquids in microchannel. A tangent hyperbolic fluid model is employed to describe the rheological behavior of the pseudoplastic fluid. Here, analytical solutions for potential distribution, temperature and nanoparticle fraction are derived and perturbation solution for stream function, pressure gradient and volumetric flow rate are obtained. The convective boundary condition is applied on the channel walls. The authentic assumptions of Debye-Hückel linearization, long wavelength and small Reynold's number are employed in the dimensional conservative equations. The influences of various emerging parameters are graphically computed for axial velocity, pressure gradient, thermal temperature, nanoparticle volume fraction, skin friction coefficient and Nusselt profiles. To observe the thermal radiation effects, a thermal radiative flux model is also deployed. It is noticed that the heat transfer Biot number increases with increasing thermal temperature; however, a reversed behavior is reported for the nanoparticle volume fraction. Therefore, the present model does not only provide a deep theoretical insight to interpret the electroosmotic flow systems, but it will also be applicable in designing the emerging tool for biomicrofluidic devices/systems under peristalsis mechanisms.

This article describes an unexplored transport phenomenon where a mildly viscoelastic medium encroaches a narrow capillary channel under the action of surface-tension force. The ultimate goal of the study is to provide the penetration length and the intrusion rate of the liquid as functions of time. The resulting analysis would be instrumental in building an inexpensive and convenient rheometric device which can measure the temporal scale for viscoelastic relaxation from the stored data of the aforementioned quantities. The key step in the formulation is a transient eigenfunction expansion of the instantaneous velocity profile. The time-dependent amplitude of the expansion as well as the intruded length are governed by a system of integro-differential relations which are derived by exploiting the mass and momentum conservation principles. The obtained integro-differential equations are simultaneously solved by using a fourth-order Runge–Kutta method assuming a start-up problem from rest. The resulting numerical solution properly represents the predominantly one-dimensional flow which gradually slows down after an initial acceleration and subsequent oscillation. The computational findings are independently verified by two separate perturbation theories. The first of these is based on a Weissenberg number expansion revealing the departure in the unsteady imbibition due to small but finite viscoelasticity. In contrast, the second one explains the long-time behaviour of the system by analytically predicting the decay features of the dynamics. These asymptotic results unequivocally corroborate the simulation inferring the accuracy of the numerics as well as the utility of the simplified mathematical models.

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Thermosolutal Marangoni boundary layer flows are of great interest due to their applications in industrial applications such as drying of silicon wafers, thin layers of paint, glues, in heat exchangers, and crystal growth in space. The present analysis deals with the effect of chemical radiation and heat absorption/generation of the viscous fluid flow on a thermosolutal Marangoni porous boundary with mass transpiration and heat source/sink. The physical flow problem is mathematically modeled into Navier–Stokes equations. These nonlinear partial differential equations are then mapped into a set of nonlinear ordinary differential equations using similarity transformation. The analytical solutions for velocity, temperature, and concentration profiles are rigorously derived. The solutions so obtained are analyzed through various plots to demonstrate the effect of various physical parameters such as mass transpiration parameter Vc, inverse Darcy number Da−1, Marangoni number Ma, Schmidt number Sc, chemical reaction coefficient (K), Prandtl number (Pr), thermal radiation parameter (NR), and the heat source/sink parameter (I) on the momentum/thermal boundary, and their physical insights are also reported.