Study of nonlinear MHD tribological squeeze film at generalized magnetic reynolds numbers using DTM.

In the current article, a combination of the differential transform method (DTM) and Padé approximation method are implemented to solve a system of nonlinear differential equations modelling the flow of a Newtonian magnetic lubricant squeeze film with magnetic induction effects incorporated. Solutions for the transformed radial and tangential momentum as well as solutions for the radial and tangential induced magnetic field conservation equations are determined. The DTM-Padé combined method is observed to demonstrate excellent convergence, stability and versatility in simulating the magnetic squeeze film problem. The effects of involved parameters, i.e. squeeze Reynolds number (N1), dimensionless axial magnetic force strength parameter (N2), dimensionless tangential magnetic force strength parameter (N3), and magnetic Reynolds number (Rem) are illustrated graphically and discussed in detail. Applications of the study include automotive magneto-rheological shock absorbers, novel aircraft landing gear systems and biological prosthetics

Analytical modeling of MHD flow over a permeable rotating disk in the presence of soret and dufour effects: Entropy analysis.

The main concern of the present article is to study steady magnetohydrodynamics (MHD) flow, heat transfer and entropy generation past a permeable rotating disk using a semi numerical/analytical method named Homotopy Analysis Method (HAM). The results of the present study are compared with numerical quadrature solutions employing a shooting technique with excellent correlation in special cases. The entropy generation equation is derived as a function of velocity, temperature and concentration gradients. Effects of flow physical parameters including magnetic interaction parameter, suction parameter, Prandtl number, Schmidt number, Soret and Dufour number on the fluid velocity, temperature and concentration distributions as well as entropy generation number are analysed and discussed in detail. Results show that increasing the Soret number or decreasing the Dufour number tends to decrease the temperature distribution while the concentration distribution is enhanced. The averaged entropy generation number increases with increasing magnetic interaction parameter, suction parameter, Prandtl number, and Schmidt number

Transitional turbulent flow in a stenosed coronary artery with a physiological pulsatile flow

The turbulence in the blood flow, caused by plaque deposition on the arterial wall, increases by the combined effect of the complex plaque geometries and the pulsatile blood flow. The correlation between the plaque geometry, the pulsatile inlet flow and the induced turbulence in a constricted artery is investigated in this study. Pressure drop, flow velocity and wall shear stress are determined for stenosed coronary artery models with three different degrees of asymmetric stenosis and for different heart working conditions. A Computational Fluid Dynamics model, validated against experimental data published in the literature, was developed to simulate the blood pulsatile flow inside a stenosed coronary artery model. The transitional flow behaviour was quantified by investigation of the changes in the turbulence kinetic energy. It was shown that the separation starts from the side of the asymmetric stenosis and spreads to its opposite side further downstream. The results suggest that there is a high risk of the formation of a secondary stenosis at a downstream distance equal to 10- times of the artery diameter at the side and bottom regions of the first stenosis due to the existence of the recirculation zones and low shear stresses. Finally, a stenosed patient specific coronary artery model was employed to illustrate the applicability of the obtained results for real geometry models. The results of this study provide a good prediction of pressure drop and blood flow rate, which can be applied in the investigation of the heart muscle workout and the required heart power.N. Freidoonimehr, M. Arjomandi, N. Sedaghatizadeh, R. Chin, and A. Zande

Influence of Stefan blowing on nanofluid flow submerged in microorganisms with leading edge accretion or ablation

The unsteady forced convective boundary layer flow of viscous incompressible fluid containing both nanoparticles and gyrotactic microorganisms, from a flat surface with leading edge accretion (or ablation), is investigated theoretically. Utilizing appropriate similarity transformations for the velocity, temperature, nanoparticle volume fraction and motile microorganism density, the governing conservation equations are rendered into a system of coupled, nonlinear, similarity ordinary differential equations. These equations, subjected to imposed boundary conditions, are solved numerically using the Runge-Kutta-Fehlberg fourth-fifth order numerical method in the MAPLE symbolic software. Good agreement between our computations and previous solutions is achieved. The effect of selected parameters on flow velocity, temperature, nano-particle volume fraction (concentration) and motile microorganism density function is investigated. Furthermore, tabular solutions are included for skin friction, wall heat transfer rate, nano-particle mass transfer rate and microorganism transfer rate. Applications of the study arise in advanced micro-flow devices to assess nanoparticle toxicity

Effect of degree of stenosis on the pulsatile flow pressure drop in a coronary artery

Artery blockage due to plaque formation affects the performance of the heart considerably. These plaques are formed inside an artery and forced the heart to work harder to feed the vessels and organs with oxygenated blood. In this study, the pressure drop of a pulsatile flow is calculated in diseased coronary arteries with different degrees of stenosis and for blood with different levels of blood viscosity. Pressure drop is much more significant at the severe degrees of stenosis (more than 60%) compared to the mild and moderate cases. The effect of changes in the level of blood viscosity on the pressure drop is more significant at early stages of atherosclerosis (mild degrees of stenosis). The comparison of the pressures measured before and after stenoses with the ones for healthy arteries is recommended to be used to estimate the severity of vessel constriction, which can be helpful in early detection of atherosclerosis via a non-invasive diagnostic procedure.N. Freidoonimehr, R. Chin, M. Arjomandi, and A. Zande

Entropy analysis of convective MHD flow of third grade non-Newtonian fluid over a stretching sheet

The purpose of this article is to study and analyze the convective flow of a third grade non-Newtonian fluid due to a linearly stretching sheet subject to a magnetic field. The dimensionless entropy generation equation is obtained by solving the reduced momentum and energy equations. The momentum and energy equations are reduced to a system of ordinary differential equations by a similarity method. The optimal homotopy analysis method (OHAM) is used to solve the resulting system of ordinary differential equations. The effects of the magnetic field, Biot number and Prandtl number on the velocity component and temperature are studied. The results show that the thermal boundary-layer thickness gets decreased with increasing the Prandtl number. In addition, Brownian motion plays an important role to improve thermal conductivity of the fluid. The main purpose of the paper is to study the effects of Reynolds number, dimensionless temperature difference, Brinkman number, Hartmann number and other physical parameters on the entropy generation. These results are analyzed and discussed

Analytical Investigation of Laminar Viscoelastic Fluid Flow over a Wedge in the Presence of Buoyancy Force Effects

An analytical strong method, the homotopy analysis method (HAM), is employed to study the mixed convective heat transfer in an incompressible steady two-dimensional viscoelastic fluid flow over a wedge in the presence of buoyancy effects. The two-dimensional boundary-layer governing partial differential equations (PDEs) are derived by the consideration of Boussinesq approximation. By the use of similarity transformation, we have obtained the ordinary differential nonlinear (ODE) forms of momentum and energy equations. The highly nonlinear forms of momentum and energy equations are solved analytically. The effects of different involved parameters such as viscoelastic parameter, Prandtl number, buoyancy parameter, and the wedge angle parameter, which is related to the exponent m of the external velocity, on velocity and temperature distributions are plotted and discussed. An excellent agreement can be seen between the results and the previously published papers for f′′(0) and θ′(0) in some of the tables and figures of the paper for velocity and temperature profiles for various values of viscoelastic parameter and Prandtl number. The effects of buoyancy parameter on the velocity and temperature distributions are completely illustrated in detail

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An analytical strong method, the homotopy analysis method (HAM), is employed to study the mixed convective heat transfer in an incompressible steady two-dimensional viscoelastic fluid flow over a wedge in the presence of buoyancy effects. The twodimensional boundary-layer governing partial differential equations (PDEs) are derived by the consideration of Boussinesq approximation. By the use of similarity transformation, we have obtained the ordinary differential nonlinear (ODE) forms of momentum and energy equations. The highly nonlinear forms of momentum and energy equations are solved analytically. The effects of different involved parameters such as viscoelastic parameter, Prandtl number, buoyancy parameter, and the wedge angle parameter, which is related to the exponent of the external velocity, on velocity and temperature distributions are plotted and discussed. An excellent agreement can be seen between the results and the previously published papers for (0) and (0) in some of the tables and figures of the paper for velocity and temperature profiles for various values of viscoelastic parameter and Prandtl number. The effects of buoyancy parameter on the velocity and temperature distributions are completely illustrated in detail

Mixed Convective Heat Transfer for MHD Viscoelastic Fluid Flow over a Porous Wedge with Thermal Radiation

The main concern of the present paper is to study the MHD mixed convective heat transfer for an incompressible, laminar, and electrically conducting viscoelastic fluid flow past a permeable wedge with thermal radiation via a semianalytical/numerical method, called Homotopy Analysis Method (HAM). The boundary-layer governing partial differential equations (PDEs) are transformed into highly nonlinear coupled ordinary differential equations (ODEs) consisting of the momentum and energy equations using similarity solution. The current HAM solution demonstrates very good agreement with previously published studies for some special cases. The effects of different physical flow parameters such as wedge angle (β) , magnetic field ( M ), viscoelastic ( k 1 ), suction/injection ( f w ), thermal radiation ( Nr ), and Prandtl number (Pr) on the fluid velocity component ( f ′( η )) and temperature distribution ( θ ( η )) are illustrated graphically and discussed in detail