Numerical computation of buoyancy and radiation effects on MHD micropolar nanofluid flow over a stretching/shrinking sheet with heat source

Abstract In this mathematical study, the effect of buoyancy parameters along with radiation on magneto-hydrodynamic (MHD) micro-polar nano-fluid flow over a stretching/shrinking sheet is taken into consideration. Suitable similarity variables are used to convert the governing non-linear partial differential equations into a system of coupled non-linear ordinary differential equations which are then numerically solved by R.K method with shooting scheme. The influence of pertinent parameters on the velocity profile, temperature profile, micro-rotation profile, and concentration profile is investigated. It is founded that the velocity profile is decreased with the increment in the values of M and the opposite behavior is noticed for micro-rotation, thermal, and concentration profiles. It is also founded that an increase in the values of buoyancy parameters causes an increase in velocity profile while micro-rotation, thermal, and concentration profiles are decreased. The results are exposed and discussed through tables and graphs

Unsteady electromagnetic radiative nanofluid stagnation-point flow from a stretching sheet with chemically reactive nanoparticles, Stefan blowing effect and entropy generation

The present article investigates the combined influence of nonlinear radiation, Stefan blowing and chemical reactions on unsteady EMHD stagnation point flow of a nanofluid from a horizontal stretching sheet. Both electrical and magnetic body forces are considered. In addition, the effects of velocity slip, thermal slip and mass slip are considered at the boundaries. An analytical method named as homotopy analysis method is applied to solve the non-dimensional system of nonlinear partial differential equations which are obtained by applying similarity transformations on governing equations. The effects of emerging parameters including Stefan blowing parameter, electric parameter, magnetic parameter etc. on the important physical quantities are presented graphically. Additionally, an entropy generation analysis is provided in this article for thermal optimization. The flow is observed to be accelerated both with increasing magnetic field and electrical field. Entropy generation number is markedly enhanced with greater magnetic field, electrical field and Reynolds number, whereas it is reduced with increasing chemical reaction parameter

Steady forced convection flow and heat transfer in a nanofluid with passive control model

The study of convective heat transfer and fluid flow has important engineering and industrial applications, for instance in the cooling of engine vehicles. Fluid such as water is commonly used as a heat transfer fluid because of its high heat capacity. Nevertheless, the limitation of water and the low thermal conductivity of other conventional heat transfer fluids could affect the efficiency of heat exchange. Therefore, a type of fluid with suspension of solid particles into base fluid, namely nanofluid was considered due to the property of nanofluid that enhances heat transfer. Mathematical models of nanofluid normally include a boundary condition that assumed nanoparticle volume fraction at the surface is constant. This boundary condition however might not be able to describe adequately the condition of nanofluid volume fraction at the boundary. Hence, a different boundary condition that considers nanoparticle mass flux at the boundary to be zero and adjusted accordingly is applied in this thesis. Recently, the use of micropolar fluid as a base fluid to nanofluid was applied in many studies. The local influence of intrinsic motion and microstructure of the fluid elements that are essential to this model of fluid can be advantageous as it can appropriately describe the types of fluid such as polymeric suspension and animal blood. Motivated by these reasons, numerical analysis of nanofluid and micropolar nanofluid flow with zero nanoparticle mass flux along with three different effects and geometries for each problem were deliberated in this thesis. The effects are viscous dissipation, Soret and Dufour, and chemical reaction, and the geometry that was investigated are moving plate, stretching plate, and wedge. In order to reduce the governing equations, series of transformation variables are used to transform the dimensional governing equations into dimensionless differential equations. The non-dimensional equations in ordinary differential equations were then solved numerically using Runge-Kutta Fehlberg. The results obtained were then compared with the limiting cases from previous study. This is done to determine the accuracy of the results published. Several parameters were examined in this thesis, namely Eckert number, Soret number, Dufour number, magnetic field, Brownian motion, thermophoresis, Lewis number, and Prandtl number. The results of reduced Nusselt number, skin friction coefficient, velocity profile, angular velocity profile, temperature profile, and concentration profile for each parameter were presented in tables and graph. It was found that the temperature and concentration profile shown a consistent result when there is an effect of viscous dissipation and chemical reaction. Temperature profile increases when thermophoresis parameter increases. In thermophoresis, the particle from the heated region is transferred to the cold region. Thus, this causes the nanofluid temperature to be increasing due to huge number of nanoparticles shifted from the hot region, which enhance the fluid temperature. Concentration profile was found to increase then decrease for both of the problems when the thermophoresis parameter and Brownian motion parameter increase. However, in the presence of Soret and Dufour, the temperature profile was found to increase when Brownian motion parameter increases, and concentration decreases then increases when the thermophoresis parameter increases. In comparison to the previous study, the difference is the temperature profile increases following an increase of Brownian motion parameter and concentration profile increase when thermophoresis increases

Non-similar radiative bioconvection nanofluid flow under oblique magnetic field with entropy generation

Motivated by exploring the near-wall transport phenomena involved in bioconvection fuel cells combined with electrically conducting nanofluids, in the present article, a detailed analytical treatment using homotopy analysis method (HAM) is presented of non-similar bioconvection flow of a nanofluid under the influence of magnetic field (Lorentz force) and gyrotactic microorganisms. The flow is induced by a stretching sheet under the action of a oblique magnetic field. In addition, nonlinear radiation effects are considered which are representative of solar flux in green fuel cells. A second thermodynamic law analysis has also been carried out for the present study to examine entropy generation (irreversibility) minimization. The influence of magnetic parameter, radiation parameter and bioconvection Rayleigh number on skin friction coefficient, Nusselt number, micro-organism flux and entropy generation number (EGN) is visualized graphically with detailed interpretation. Validation of the HAM solutions with published results is also included for the non-magnetic case in the absence of bioconvection and nanofluid effects. The computations show that the flow is decelerated with increasing magnetic body force parameter and bioconvection Rayleigh number whereas it is accelerated with stronger radiation parameter. EGN is boosted with increasing Reynolds number, radiation parameter and Prandtl number whereas it is reduced with increasing inclination of magnetic field

Steady and unsteady mhd mixed convection flow of casson and casson nanofluid over a nonlinear stretching sheet and moving wedge

Casson fluid is a shear thinning fluid which is one of the non-Newtonian fluids that exhibit yield stress. In this fluid, if a shear stress less than the yield stress is applied, it behaves like a solid, whereas if vice-versa the fluid starts to move. The advantage of Casson fluid is that it can be reduced to Newtonian fluid at very high wall shear stress. Due to these reasons, the steady and unsteady two-dimensional, electrically conducting mixed convection flow of Casson fluid was studied in this thesis. Flow that was generated due to nonlinear stretching sheet and moving wedge filled with and without nanoparticles were given attention. Specific problems were studied with various effects include, porous medium, thermal radiation, chemical reaction, slip and convective boundary conditions. Similarity transformations were used to convert nonlinear governing equations into nonlinear ordinary differential equations. The obtained equations were then solved numerically via the implicit finite difference scheme, known as Keller-box method. Moreover, an algorithm was developed in MATLAB software in order to obtain the numerical solutions. The accuracy of the numerical results was validated through comparison with the results available in the published journal. The effects of pertinent parameters on velocity, temperature and concentration profiles as well as wall shear stress, heat and mass transfer rates were displayed graphically and also presented in tabular form. Findings reveals that, when Casson fluid parameter increases the momentum boundary layer thickness reduces in both cases, nonlinear stretching sheet and moving wedge. It is noticed that in the case of moving wedge, the strength of magnetic parameter reduces the wall shear stress. Whereas, opposite trend is observed in the case of nonlinear stretching sheet. In both geometries, the influence of Brownian motion and thermophoresis parameters on the nanoparticles concentration is notably more pronounced