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A numerical simulation is performed to investigate Newtonian physiological flows behavior on three dimensional idealized carotid artery (CA) and single stenosed (75% by area) carotid artery(SCA). The wall vessel is set as rigid during simulation. Bifurcated blood vessel are simulated by using three-dimensional flow analysis. Physiological and parabolic velocity profiles are set out to fix the conditions of inlet boundaries of artery. In other hand, physiological waveform is an important part of compilation and it is successfully done by utilization of Fourier series having sixteen harmonics. The investigation has a Reynolds number range of 94 to 1120. Low Reynolds number k - ω model has been used as governing equation. The investigation has been carried out to characterize the flow behavior of blood in two geometry, namely, (i) Normal carotid artery (CA) and (ii) Stenosed carotid artery (SCA). The Newtonian model has been used to study the physics of fluid. The findings of the two models are thoroughly compared in order to observe there behavioral sequence of flows. The numerical results were presented in terms of velocity, pressure, wall shear stress distributions and cross sectional velocities as well as the streamlines contour. Stenosis disturbs the normal pattern of blood flow through the artery as reduced area. At stenosis region velocity and peak Reynolds number rapidly increase and Reynolds number reach transitional and turbulent region. These flow fluctuation and turbulence have bad effect to the blood vessel which makes to accelerate the progress of stenosis. [ABSTRACT FROM AUTHOR]

A radiative heat and mass transfer study of Walter's memory flow along a vertical cone with thermophoresis is completed in the presence of induced magnetic field. A mathematical model of Walter's memory flow is developed from the basis of studying Magnetohydrodynamics(MHD). Some dimensionless quantities have been used to transform the model to non-dimensional system of equations. The dimensionless unsteady, coupled and non-linear partial differential conservation equations for the boundary layer regime are solved by an efficient, accurate and unconditionally stable finite difference scheme of the Crank-Nicolson type. The features of the flow, heat and mass transfer characteristics within the boundary layer are analyzed by plotting graphs and the physical aspects are discussed in detail. The obtained results show that the impact of flow variables plays an important role in the Walter's memory flow. Last of all, some important findings of the present problem are concluded in this work. [ABSTRACT FROM AUTHOR]

A numerical simulation to investigate the Non-Newtonian modelling effects on physiological flows in a three dimensional idealized artery with a single stenosis of 85% severity. The wall vessel is considered to be rigid. Oscillatory physiological and parabolic velocity profile has been imposed for inlet boundary condition. Where the physiological waveform is performed using a Fourier series with sixteen harmonics. The investigation has a Reynolds number range of 96 to 800. Low Reynolds number k - ω model is used as governing equation. The investigation has been carried out to characterize two Non- Newtonian constitutive equations of blood, namely, (i) Carreau and (ii) Cross models. The Newtonian model has also been investigated to study the physics of fluid. The results of Newtonian model are compared with the Non-Newtonian models. The numerical results are presented in terms of pressure, wall shear stress distributions and the streamlines contours. At early systole pressure differences between Newtonian and Non-Newtonian models are observed at pre-stenotic, throat and immediately after throat regions. In the case of wall shear stress, some differences between Newtonian and Non-Newtonian models are observed when the flows are minimum such as at early systole or diastole. [ABSTRACT FROM AUTHOR]

An analytical solution of mixed convection flow of viscoelastic fluid in a channel with walls transpiration is obtained by optimal homotopy asymptotic method. Comparison with previous recorded result through reduction in pertinent parameters unveils the presented optimal series solution is correct. The result valid for non-transpiration walls for the values from the pertinent flow parameters could be derived as a special case from the present analysis. The results show that the proposed method is effective and has a distinct advantage over usual approximation methods in that the approximate solution obtained here is valid not only for weakly nonlinear equations, but also for strongly nonlinear ones. Second order approximation is needed for velocity while only first order temperature is needed to obtain desired results. [ABSTRACT FROM AUTHOR]

This study investigates the validity of the nonequilibrium equality called the Jarzynski equality or the work fluctuation theorem for a simple stochastic model of a Brownian particle in a trap harmonic potential. A viscoelastic fluid is adopted as well as a purely viscous fluid for the ambient fluid. It is found that there is a case where the Jarzynski equality does not hold. The key factor for the validity of the Jarzynski equality is the time-scale of the dynamics, which should be determined when the system is modeled in the stochastic Langevin dynamics. [ABSTRACT FROM AUTHOR]

In this work we report theoretical and numerical results on convection for a binary magnetic mixture in a viscoelastic carrier liquid. We focus in the stationary and oscillatory convection for idealized boundary conditions and we obtain explicit expressions of convective thresholds in terms of the control parameters of the system. The effect of the magnetophoresis and Kelvin force are emphasized. Finally, we analyze the effect of the rheology on instability thresholds for a diluted suspensions. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

In many polymer processing applications filler particles such as glass beads are added to the polymer matrix. To study the rheology of such multiphase systems we perform direct simulations of the motion of the suspended particles when subjected to an external linear flow, such as simple shear or planar extensional flow. The method uses a Lagrangian finite element grid that deforms with fluid combined with a quotient representation of the periodic computational domain. For shear flow we show that one can predict the viscometric properties of the suspension for shear thining fluid by using a simple shifting model. For planar extensional flow it is found that adding particle suppressed the extend of strain hardening in strongly strain-hardening fluids. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

We present experimental results and tentative explanations for the origin of sharkskin in extrusion of polyolefins with narrow molecular weight distribution as well as plausible mechanisms of sharkskin suppression by the use of viscoelastic Polymer Processing Additives (PPA). Novel PPAs are proposed. The novel PPAs are composed of esters of oxoacids of Boron and Phosphorus and Polyethylene Glycol (PEG) with molecular weights from 1000 to 10,000 Da, and optionally contain silanols and a thickening agent. In contrast to conventional PPAs made from fluorinated polymers and siloxanes, the novel PPAs are hydrophilic and they can be made from cheap and FDA-compliant components. [ABSTRACT FROM AUTHOR]

Elastic particles are often added to polymer melts as impact modifiers. Unlike rigid fillers, elastic particles can deform during flow and so modify the rheology of the polymer melt. To study the rheology of such multiphase systems we perform direct simulations of the motion of elastic particles in a viscoelastic matrix when subjected to an external linear flow, such as shear or planar extensional flow. The method uses a finite element solution of the flow in a unit cell within a self-replicating lattice. In shear flow our method is equivalent to the Lees-Edwards boundary condition[l], while in extension we use the Kraynik-Reinelt cell structure [2] that provides a self-replicating lattice. This allows simulations to be carried out for large strains. The continuous phase is modelled using different constitutive models such as OldroydB model and the pom-pom model. In shear flow, we found that isotropic filler particles deform into ellipses. However, unlike rigid elliptical particles which rotate during shear flow, elastic particles perform a “tank-treading” motion in which the surface of the particle rotates around their centre of mass, but bounding shape remains fixed. The shear viscosity is found to be lower than for a polymer filled with rigid particles, however, there is now a phase lag due to the particle elasticity. For planar extensional flows we found that the filled particles become stretched in the direction of extension and the strain hardening or softening of polymer melts is strongly correlated with the deformation of the particle. [ABSTRACT FROM AUTHOR]