Soret and MHD effects on bioconvection wall jet flow of nanofluid containing gyrotactic microorganisms

Various applications of bioconvection phenomena in the field of medicine and biotechnology boost us to present the study of laminar wall jet flow in this specific direction. For the purpose, we have considered nanofluid containing gyrotactic microorganisms in the presence of normally applied magnetohydrodynamic forces along with Soret effects. Boundary layer approximation and similarity transformation are utilized to convert governing equations into ordinary differential equations. Influence of different emerging parameters on velocity, temperature and concentration profiles of solute, nanoparticle and motile microorganisms has been investigated. The role of physical quantities like Nusselt number, Sherwood number and density number of microorganisms is also highlighted. Increase in Nusselt number and density number of motile microorganism is observed for incremental values of bioconvection Peclet number. Soret number reflects increasing effect on Nusselt number and decreasing effect on Sherwood number because solute diffusion faces resistance due to higher values of Soret number and in return decreases rate of mass transfer. Also bioconvection Rayleigh number imposes decreasing effect on density number of the motile microorganisms.

     

Hydromagnetic nanofluid flow past a stretching cylinder embedded in non-Darcian Forchheimer porous media

The present article presents the hydromagnetic nanofluid flow past a stretching cylinder embedded in non-Darcian Forchheimer porous media by using Buongiorno’s mathematical model (Buongiorno in J Heat Transf 128:240–250, 2006; Nadeem et al. in J Taiwan Inst Chem Eng 45:121, 2014, Nadeem et al. Appl Nanosci 4:625–631, 2014). Thermal radiation via Roseland’s approximation (Akbar et al. in Chin J Aeronaut 26:1389–1397, 2013; Nadeem and Haq in J Aerosp Eng 28:04014061, 2012), Brownian motion, thermophoresis and Joule heating effects are also considered. To explore thermal characteristics, prescribed heat flux and prescribed mass flux boundary conditions are deployed. Governing flow problem consists of PDEs in the cylindrical form, which are converted into system of nonlinear ODEs by applying applicable similarity transforms. ODEs are tackled by RK–Fehlberg fourth–fifth-order numerical integration scheme with shooting algorithm. Impact of numerous involving physical parameters on flow features like temperature distribution, velocity distribution, Sherwood number, local Nusselt number and skin friction coefficient is shown through graphs and tables.

     

Molecular dynamics simulation of flow past a plate

Molecular dynamics simulations with a soft-sphere potential have been carried out to model two dimensional fluid flow obstructed by a plate. At fluid velocities large enough to obtain adequate signal to noise resolution, two counter-circulating vortices are observed behind the obstruction. The stationary state length scale of these vortices is found to be roughly proportional to the average velocity in the system, as predicted by the hydrodynamic theory.     

A mathematical model of MHD nanofluid flow having gyrotactic microorganisms with thermal radiation and chemical reaction effects

In this article, we have examined three-dimensional unsteady MHD boundary layer flow of viscous nanofluid having gyrotactic microorganisms through a stretching porous cylinder. Simultaneous effects of nonlinear thermal radiation and chemical reaction are taken into account. Moreover, the effects of velocity slip and thermal slip are also considered. The governing flow problem is modelled by means of similarity transformation variables with their relevant boundary conditions. The obtained reduced highly nonlinear coupled ordinary differential equations are solved numerically by means of nonlinear shooting technique. The effects of all the governing parameters are discussed for velocity profile, temperature profile, nanoparticle concentration profile and motile microorganisms’ density function presented with the help of tables and graphs. The numerical comparison is also presented with the existing published results as a special case of our study. It is found that velocity of the fluid diminishes for large values of magnetic parameter and porosity parameter. Radiation effects show an increment in the temperature profile, whereas thermal slip parameter shows converse effect. Furthermore, it is also observed that chemical reaction parameter significantly enhances the nanoparticle concentration profile. The present study is also applicable in bio-nano-polymer process and in different industrial process.

     

Two dimensional boundary layer flow with heat and mass transfer of magneto hydrodynamic non-Newtonian nanofluid through porous medium over a semi-infinite moving plate

Microsystem Technologies - Steady two-dimensional motion of an incompressible non-Newtonian Nanofluid through porous medium over a semi-infinite moving plate is studied . The system is stressed by...     

Viscous flow past a porous sphere within a nonconcentric fictitious spherical cell

Microsystem Technologies - The quasi steady axisymmetrical flow of an incompressible viscous fluid past an assemblage of porous sphere situated at an arbitrary position within a virtual spherical...     

MHD flow of radiative micropolar nanofluid in a porous channel: optimal and numerical solutions

The flow of a radiative and electrically conducting micropolar nanofluid inside a porous channel is investigated. After implementing the similarity transformations, the partial differential equations representing the radiative flow are reduced to a system of ordinary differential equations. The subsequent equations are solved by making use of a well-known analytical method called homotopy analysis method (HAM). The expressions concerning the velocity, microrotation, temperature, and nanoparticle concentration profiles are obtained. The radiation tends to drop the temperature profile for the fluid. The formulation for local Nusselt and Sherwood numbers is also presented. Tabular and graphical results highlighting the effects of different physical parameters are presented. Rate of heat transfer at the lower wall is seen to be increasing with higher values of the radiation parameter while a drop in heat transfer rate at the upper wall is observed. Same problem has been solved by implementing the numerical procedure called the Runge–Kutta method. A comparison between the HAM, numerical and already existing results has also been made.

     

Convective Poiseuille flow of Al2O3-EG nanofluid in a porous wavy channel with thermal radiation

In current article, convective Poiseuille boundary layer flow of ethylene glycol (C₂H₆O₂)-based nanofluid with suspended aluminum oxide (Al₂O₃) nanoparticles through a porous wavy channel has been examined. The impact of thermal radiation, Ohmic dissipation, electric field, and magnetic fields are also considered. The flow is due to constant pressure gradient in a wavy frame of reference. The governed momentum and thermal boundary layer equations is system of PDE’s, which are converted to system of ODE’s via suitable similarity transformations. The homotopy analysis method is applied to solve the governed flow problem. Convergence of series solutions is inspected through h-curves and residual errors norm, whereas the optimal value of convergence control parameter is obtained by means of genetic algorithm Nelder–Mead approach. The influence of numerous involving parameters like Hartmann number, Grashof number, Eckert number, electric parameter, radiation parameter, and porosity parameter on flow, heat transfer, skin friction coefficient and Nusselt number are illustrated through graphs and discussed briefly.

     

Vortex instability of MHD natural convection flow over a horizontal plate in a porous medium

The present work investigates the vortex instability of a horizontal MHD natural convection boundary layer flow in a saturated porous medium including the radiation effect. The numerical results are solves by Keller-Box method incorporated with linear stability theory. The velocity and temperature profiles, local Nusselt number, as well as instability parameters for magnetic parameter M ranging from 0 to 2 and radiation parameter R ranging from 0 to 0.03 are presented. Numerical results showed that, as magnetic parameter M increases or radiation parameter R decreases, the heat transfer rate decrease. In addition, the magnetic effect destabilizes the flow to vortex mode of disturbance, while the radiation effect stabilizes it.     

MHD flow with heat and mass transfer of Williamson nanofluid over stretching sheet through porous medium

Microsystem Technologies - Two-dimensional hydromagnetic flow of an incompressible Williamson nanofluid over a stretching sheet in a porous media is examined during this work. Convective heat and...     

Lie group analysis of stagnation-point flow of a nanofluid

This article concerns with a steady two-dimensional boundary layer flow of an electrically conducting incompressible nanofluid over a stretching sheet in a porous medium with internal heat generation/absorption. The transport model includes the effect of Brownian motion with thermophoresis in the presence of chemical reaction and magnetic field. Lie group analysis is applied to the governing equations. The transformed self similar non-linear ordinary differential equations along with the boundary conditions are solved numerically. The influences of various relevant parameters on the flow field, temperature and nanoparticle volume fraction as well as wall heat flux and wall mass flux are elucidated through graphs and tables.     

Steady flow past a rotating cylinder

Numerical solutions have been obtained for steady viscous flow past a rotating circular cylinder. Results are presented for Reynolds numbers of 5 and 20 and ratios of the speed of the surface of the cylinder to the fluid speed at infinity from 0 to 0.5. The effects of using different boundary conditions on the stream function at large distances from the cylinder are presented and discussed.     

Flow past an array of cells that are adherent to the bottom plate of a flow channel

Parallel-plate flow channels are used extensively in cell-biological research to investigate cell-substrate adhesion. However, an analytical relationship between the fluid force acting on a cell that is adherent to the bottom plate of a channel and the flow rate into the channel is yet to be established. A finite-difference scheme was used to evaluate the three-dimensional laminar flow past an array of uniformly distributed cells that are adherent to the bottom plate of a parallel-plate flow channel. Computational results indicated that the fluid force acting on a spherical cell can be computed within 10% accuracy by using the solution given by Goldman et al. [Goldman, A. J., Cox, R. G. and Brenner, H., Slow viscous motion of a sphere parallel to a plane wall. I. Motion through quiescent fluid. Chem. Engng Sci., 1967, 22, 637–651. Goldman, A. J., Cox, R. G. and Brenner, H., Slow viscous motion of a sphere parallel to a plane wall. II. Couette flow. Chem. Engng Sci., 1967, 22, 653–660.] — for a single sphere in contact with a planar wall in infinite shear flow — when the ratio of the cell radius (R_S) to the gap thickness between parallel plates (h) is less than (1/15). Goldman et al.'s solution begins to significantly overestimate the actual fluid force as the (R_S/h) ratio becomes larger than 1/15. When R_S/h) = 1/5, the fluid force computed by Goldman et al. is greater than the actual force by 30%. As an originally spherical cell aligns and elongates in the direction of flow, the fluid force acting on it decreases by 25%. In all cases, cell spreading leads to a more uniform distribution of fluid shear stress on the cell surface. Further computations indicate that fluid force on a spherical cell with surface projections (rough cell) is slightly smaller than that for a smooth spherical cell whose radius is equal to the maximum radial dimension of the rough cell.     

Numerical approach for nanofluid transportation due to electric force in a porous enclosure

Microsystem Technologies - In current attempt, nanoparticle Electrohydrodynamic transportation has been modeled numerically via control volume based finite element method. Mixture of Fe3O4 and...     

Effects of lubrication in the oblique stagnation-point flow of a nanofluid

This study investigates the oblique flow of a nanofluid near a stagnation point past a lubricated plate. A power-law fluid is utilized for lubrication. A suitable set of transformation is utilized to obtain system of dimensionless governing equations. A well-known numerical technique known as Keller-box method is employed to get the similar solution. Influence of emerging parameters on the flow characteristics has been discussed in the presence of lubrication through graphs and numerical data ranging from no slip (\(\beta \to \infty )\) to full slip (\(\beta \to 0)\). Impact of thermophoresis and Brownian motion is further investigated. A comparison in the special cases between the present and published data validates this work.     

Hysteresis in flow past a NACA 0012 airfoil

Computations for two-dimensional flow past a stationary NACA 0012 airfoil are carried out with progressively increasing and decreasing angles of attack. The incompressible, Reynolds averaged Navier–Stokes equations in conjunction with the Baldwin–Lomax model, for turbulence closure, are solved using stabilized finite element formulations. Beyond a certain angle of attack the flow stalls with a sudden loss of lift and increase in drag. Hysteresis in the aerodynamic coefficients is observed for a small range of angles of attack close to the stall angle. This is caused by the difference in the location of the separation point of the flow on the upper surface of the airfoil during the increasing and decreasing angles of attack. With the increasing angle, the separation point moves gradually towards the leading edge. With the decreasing angle, the movement of the separation point away from the leading edge is abrupt.     

Unsteady potential flow past a group of spheres

The problem of an unsteady potential flow past a group of stationary spheres is considered using the methods of images. The problem is formulated so that the number and location of the spheres is arbitrary so long as there is no overlap between adjacent spheres. Inertial and lift coefficients are determined for several different sphere arrangements. The inertial coefficient for a sphere can vary in either direction from its isolated-sphere value of 1·5. The controlling factors on this variation are the relative geometric position of the sphere within the group and its distance from its neighbors. These same factors determine, as is expected, the lift-coefficient values. In some example configurations, there is even a drag-type force generated on an individual sphere in the potential flow.     

Viscoelastic flow past a cylinder: drag coefficient

The channel flow of a viscoelastic fluid past a circular cylinder is simulated using a parallelized unstructured Finite Volume Method (FVM) [H.-S. Dou, N. Phan-Thien, J. Non-Newtonian Fluid Mech. 77 (1998) 21–51] under a distributed computing environment through the Parallel Virtual Machine (PVM) libraries. The numerical method is based on the SIMPLER (Semi-Implicit Method for Pressure-Linked Equations Revised) algorithm, using the simplified Phan-Thien/Tanner (PTT) and the Upper Convective Maxwell (UCM) constitutive models, with the Elastic Viscous Split Stress (EVSS) formulation. The parallelization of the program is implemented by a domain decomposition strategy and the PVM software. It is found that the both shear thinning and normal stress contribute to the drag reduction. With the PTT model, the drag reduction is mainly due to shear thinning. With the UCM model, it is primarily due to the normal stress effect.     

Simulations of subsonic vortex-shedding flow past a 2D vertical plate in the near-continuum regime by the parallelized DSMC code

A general-purpose Parallel Direct Simulation Monte Carlo Code, named PDSC, is used to simulate near-continuum subsonic flow past a 2D vertical plate for studying the vortex-shedding phenomena. An unsteady time-averaging sampling method and a post-processing procedure called DREAM (DSMC Rapid Ensemble Averaging Method) have also been implemented, reducing the overall computational expense and improving the sampling quality of time-dependent flow problems in the rarefied flow regime. Parametric studies, including the temporal variable time step (TVTS) factor, the number of particles per cell, the domain size, and the Reynolds number, have been conducted, obtaining the Strouhal number and various aerodynamic coefficients of the flow. Results are compared to experimental data in the continuum regime available in the literature, demonstrating the capacity of PDSC and DREAM to simulate near-continuum vortex-shedding problems within acceptable computational time.