The objective of present communication is to discuss the effect of mass convective condition on the peristaltic transport of viscous fluid in an asymmetric channel. Analysis has been carried out in the presence of Soret and Dufour effects. Comparative study of temperature and concentration fields in the presence and absence of convective conditions through heat and mass transfer is carefully examined. Numerical values of heat and mass transfer rates are computed and analyzed.

This article addresses the abilities and limitations of the Lattice Boltzmann (LB) method in solving advection-dominated mass transport problems. Several schemes of the LB method, including D2Q4, D2Q5, and D2Q9, were assessed in the simulation of two-dimensional advection-dispersion equations. The concept of Single Relaxation Time (SRT) and Multiple Relaxation Time (MRT) in addition to linear and quadratic Equilibrium Distribution Functions (EDF) were taken into account. The results of LB models were compared to the well-known Finite Difference (FD) solutions, including Explicit Finite Difference (EFD) and Crank-Nicolson (CN) methods. All LB models are more accurate than the aforementioned FD schemes. The results also indicate the high potency of D2Q5 SRT and D2Q9 SRT in describing advection-controlled mass transfer problems. The numerical artificial oscillations are observed when the Grid Peclet Number (GPN) is greater than 10, 25, 20, 25, and 10 regarding D2Q4 SRT, D2Q5 SRT, D2Q5 MRT, D2Q9 SRT and D2Q9 MRT, respectively, while the corresponding GPN values obtained for the EFD and CN methods were 2 and 5, respectively. Finally, a coupled system of groundwater and solute transport equations were solved satisfactorily using several LB models. Considering computational time, all LB models are much faster than CN method.

Both micro electro mechanical systems (MEMS) based and lab-on-a chip (LoC) devices demand efficient micro-scale mixing mechanisms for its effective control which necessitates the quality research towards more efficient designs. A new venture is investigated in those direction with mixing micro-channel constricted with rectangular block under pressure-driven electro-osmotic flow and is numerically simulated by a modified immersed boundary method (IBM), an alternative technique in computational fluid dynamics (CFD). The electro-osmotic flow elucidated by electrical double layer theory when simultaneously considered with pressure driven flow in micro channels can be effectively figured out by the solution of Navier-Stokes equations linked with Nernst-Planck and Poisson equations for transportation of ion and electric field respectively. In this study, the effect of varying the height of rectangular block on the flow and mixing performance are analyzed. A hybrid method, which is a combination of active and passive techniques, is introduced simultaneously in the micro-channel by the electro-osmotic effects and channel constriction. The approach is on the basis of finite volume methodology on a staggered mesh. The governing equations are solved by a time-integration technique based on a fractional step method. The velocity fields are corrected by a pseudo-pressure term to ensure the continuity in each computational time step. The extent of mixing in every cross section of the micro channel is assessed by a suitable mixing efficiency parameter. This study has shed light on the most predominant factors that influence mixing efficiency in a micro-channel, such as geometry of the block, non-dimensional numbers (Reynolds number, Re and Peclet number, Pe), zeta potential, external electric field strength and electrical double layer (EDL) thickness. The maximum efficiency in this micro mixer design is found to be 51. 3% for Reynolds number of 0. 05 and Peclet number of 450 with the rectangular block height of 0. 75. It is clear that both electro osmotic effects and flow perturbations due to channel constriction caused a remarkable improvement in mixing efficiency. The outcomes of this investigation are widely applicable in cooling of microchips, heat sinks of MEMS based devices, drug delivery applications and Deoxyribonucleic acid (DNA) hybridization. The present IBM model is validated by experimental and numerical results from the literature.

A thermodynamic model was used to find out the optimum temperature for the growth of ZnS single crystals in closed ampoules by chemical vapor transport technique. Based on this model 1002oC was found to be optimum temperature for 2 mg/cm3 concentration of transporting agent (iodine). ZnS Crystals were grown in optimum (1002oC) and non-optimum (902oC and 1102oC) temperatures. The composition structure and microstructure of the grown crystals were studied by Atomic absorption spectroscopy, X-ray diffraction and Scanning electron microscopy measurements. Properties of the grown crystals were correlated to the growth conditions especially a stability in mass transport along the closed tube length.

It has been explored the unsteady MHD convection flows during loosely packed permeable media into a precipitately starting perpendicular plate by the changeable temperature as well as mass transportation. The temperature of the plate rises linearly over time. The fluid taken is as gray engrossing, or emitted and radiating but the non-scattering media. The governing equations of the current investigation are resolved by the Laplace transformation methodology. The velocity, temperature, as well as concentration, are found systematically and numerically explored for various governing parameters. Also, the skin friction, Nusselt number, and Sherwood numbers by the combinations of distinct flow parameters are demonstrated in graphical profiles, as well as physical features of the problem are explored. It is found that the magnitude of the velocity is increased by enhancement into the quantities of penetrability parameter. The magnitude of the velocity is enhanced as it trims down incessantly by increasing into the radiating parameter. The velocity increases over time. The magnitude of the velocity is decreased by an increase in the Prandtl number. The temperature is reduced by an increase in the radiating parameters and/or Prandtl numbers. The growing quantities of the Schmidt number led to the concentration profile complete liquid area. Nusselt number is growing by increasing into radiating parameter and Prandtl number.