We analyze the peristaltic motion of aqueous electrolytes altered by means of applied electric fields. Handling electrolytes in typical peristaltic channel material such as polyvinyl chloride and Teflon leads to the generation of a net surface charge on the channel walls, which attracts counter-ions and repels co-ions from the aqueous solution, thus leading to the formation of an electrical double layer—a region of net charges near the wall. We analyze the spatial distribution of pressure and wall shear stress for a continuous wave train and single pulse peristaltic wave in the presence of an electrical (electroosmotic) body force, which acts on the net charges in the electrical double layer. We then analyze the effect of the electroosmotic body force on the particle reflux as elucidated through the net displacement of neutrally buoyant particles in the flow as the peristaltic waves progress. The impact of combined electroosmosis and peristalsis on trapping of a fluid volume (e.g., bolus) inside the travelling wave is also discussed. The present analysis goes beyond the traditional analysis, which neglects the possibility of coupling the net pumping of fluids due to peristalsis and allows us to derive general expressions for the pressure drop and flow rate in order to set up a general framework for incorporating flow control and actuation by simultaneous peristalsis and application of electric fields to aqueous solutions. It is envisaged that the results presented here may act as a model for the design of lab-on-a-chip devices.

An extended lattice Boltzmann model is developed for simulating the convection–diffusion phenomena associated with solid–liquid phase transition processes. Macroscopic hydrodynamic variables are obtained through the solution of an evolution equation of a single-particle density distribution function, whereas, the macroscopic temperature field is obtained by solving auxiliary scalar transport equations. The novelty of the present methodology lies in the formulation of an enthalpy-based approach for phase-change modelling within a lattice-Boltzmann framework, in a thermodynamically consistent manner. Thermofluidic aspects of phase transition are handled by means of a modified enthalpy–porosity formulation, in conjunction with an appropriate enthalpy-updating closure scheme. Lattice-Boltzmann simulations of melting of pure gallium in a rectangular enclosure, Rayleigh–Bénard convection in the presence of directional solidification in a top-cooled cavity, and crystal growth during solidification of an undercooled melt agree well with the numerical and experimental results available in the literature, and provide substantial evidence regarding the upscaled computational economy provided by the present methodology.

In this paper, a novel mathematical approach is devised to analyze the flow of blood from a droplet into a microcapillary channel. Special attention is devoted to estimate the effects of variable hydraulic resistance over different flow regimes, influence of suspended RBC particulates on the non-Newtonian flow characteristics and implications of a dynamically-evolving contact angle. Flow characteristics depicting advancement of the fluid within the microfluidic channel turn out to be typically non-linear, as per relative instantaneous strengths of the capillary forces and viscous resistances. It is found that the greater the ‘pseudoplasticity’ of the blood, the weaker the retarding shear forces. The driving forces, on the other hand, become stronger with time, on account of a reduction of contact angle with a decrease of blood flow velocity, although this strengthening is less prominent for blood samples with greater ‘pseudoplasticity’. It is revealed that RBCs suspended in blood samples have a strong influence on the effective blood viscosity, and consequently, may drive the fluid significantly faster into the microchannel, especially when the characteristic length scales of the suspensions approach the hydraulic radius of the channel.