Computational model on pulsatile flow of blood through a tapered arterial stenosis with radially variable viscosity and magnetic field

An unsteady two-fluid model of blood flow through a tapered arterial stenosis with variable viscosity in the presence of variable magnetic field has been analysed in the present paper. In this article, blood in the core region is assumed to obey the law of Jeffrey fluid and plasma in the peripheral layer is assumed to be Newtonian. The values for velocity, wall shear stress, flow rate and flow resistance are numerically computed by employing finite-difference method in solving the governing equations. A comparison study between the velocity profiles obtained by the present study and the experimental data represented graphically shows that that the rheology of blood obeys the law of Jeffrey fluid rather than that of Newtonian fluid. The effects of parameters such as taper angle, radially variable viscosity, hematocrit, Jeffrey parameter, magnetic field and plasma layer thickness on physiologically important parameters such as wall shear stress distribution and flow resistance have been investigated. The results in the case of radially variable magnetic field and constant magnetic field are compared to observe the effect of magnetic field in driving the blood flow. It is observed that increase in hematocrit increases the wall shear stress. The values of wall shear stress and flow resistance are obtained at various time instances and compared. It is pertinent to note that the magnitudes of flow resistance are higher in the case of converging tapered than non-tapered and diverging tapered artery.     

Effect of magnetic properties of a composite superconductor on losses in variable magnetic field. Part 2: Experiment

The theory developed in Part 1 of this paper is compared with the results of experimental measurements of losses in multi-filamentary superconductors in a transverse field. The losses have been measured for different magnetic field variation patterns (sinusoidal, triangular, trapezoidal, single pulses). The numerical results obtained with the aid of the theory are in fairly good agreement with the experimental data. In the majority of the actual cases, analytical expressions for losses can be used.     

Effect of magnetic properties of a composite superconductor on the losses in a variable magnetic field: Part 3 collective interaction of turns

The results obtained in Parts 1 and 2 of this paper were for a solitary conductor in an external magnetic field. However, the magnetization of the other winding turns has a considerable effect on losses in a variable magnetic field. A theoretical treatment of the phenomena associated with the collective interaction of turns is presented. The experimental results obtained on samples of different geometry are in a good agreement with theory.     

Effect of a transverse magnetic field on the structure of a turbulent flow of mercury behind a sudden expansion

Journal of Engineering Physics and Thermophysics -     

Stagnation flow and heat transfer in a zonal magnetic field

Summary The problem stated in the title is studied for small values of the diffusivity ratio and the magnetic force coefficient , the magnetic field being of internal origin. Uniformly valid expansions are derived for the velocity and magnetic fields in the fluid. It is found that as 1, the viscous layer is brought to rest and the current in the layer is uniform and normal to the wall.The heat transfer is next calculated at a uniformly heated wall on the assumption of small temperature variations. It is deduced that when log(^–1) approaches a certain value depending on the wall temperature etc., the thermal boundary layer separates at the stagnation point and, if dissipation is neglected, along the whole wall.     

The effect of magnetic properties of a composite superconductor on the losses in variable magnetic field: Part 1 theory

Equations have been derived which describe the behaviour of a composite superconductor in a variable magnetic field. The conductor is treated as a magnet of variable permeability which may be increased over the entire range of magnetization of superconducting filaments. A numerical solution to these equations will determine the losses per field variation cycle. The proposed concept of mean incremental permeability leads to some solutions in the closed form.     

Effect of pressure on plasma sheath in a magnetic field

The effects of collisions on plasma sheath in an external magnetic field have been investigated by considering the collisions between ions and neutral gas atoms. The ion fluid equations containing an external magnetic field and the collisions are solved numerically to study the ion dynamics under various pressures.     

Elastic effects in the flow of polymer solutions in channels of variable cross section and a porous medium

The manifestation of elastic effects during the filtration of polymer solutions is analyzed theoretically.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 49, No. 3, pp. 390–397, September, 1985.     

Capillary magnetic field flow fractionation and analysis of magnetic nanoparticles

This paper reports the purification and analysis of magnetic nanoparticles using capillary magnetic field flow fractionation, which utilizes an applied magnetic field oriented orthogonal to the capillary flow. To validate this approach as a separation method for nanometer-scale particles, samples of magnetic nanoparticles composed of either gamma-Fe2O3 (maghemite) or CoFe2O4 with average diameters ranging from 4 to 13 nm were prepared and characterized by transmission electron microscopy and SQUID magnetometry. Retention of the samples on the capillary was investigated as a function of solvent flow rate and the nanoparticle size and composition; the elution times of the nanoparticles are strongly dependent on their magnetic moments. We demonstrate the use of this method to separate a mixture of nanoparticles into size-monodisperse fractions. The magnetic moments of the particles are calculated based on analysis of the retention parameters and correlate with values obtained in separate SQUID magnetometry measurements.     

Phase-slip centers of superconducting indium bridges with variable thickness in a magnetic field

We have measured current-voltage (I–V) curves in magnetic fieldsH, for indium variable-thickness bridges whose strips were quasi-one-dimensional superconductors. TheI–V curves take three different types depending on theH regions. One has hysteresis due to phase-slip centers. The others have no hysteresis. The critical current againstH shows hysteresis owing to the surface currents induced byH. The modification of the pair-breaking time was introduced to treat theH dependence of the hysteresis ofI–V curves.     

Biofluid flow in a channel under the action of a uniform localized magnetic field

In this work the fundamental problem of the biomagnetic (blood) fluid flow in a channel under the influence of a steady localized magnetic field is studied. For the mathematical formulation of the problem both magnetization and electrical conductivity of blood are taken into account and blood is considered as a homogeneous Newtonian fluid. For the numerical solution of the problem, which is described by a coupled, non linear system of PDEs, with appropriate boundary conditions, the stream function–vorticity formulation is adopted. The solution is obtained by the development of an efficient numerical technique based on finite differences. Results concerning the velocity and temperature field, skin friction and rate of heat transfer, indicate that the presence of the magnetic field influences considerably the flow field. It is also obtained that the electrical conductivity of blood should be taken into account at the area of the uniform magnetic field.     

Experimental study of circular couette flow in a coplanar magnetic field

We present and discuss results from an experimental investigation of the hydrodynamic parameters of circular Couette flow in a coplanar magnetic field: the velocity profiles, the oscillograms showing the pulsations in total and static mercury heads, and the relationship between the coefficient of friction at the wall and the dimensionless Reynolds and Hartmann numbers.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 16, No. 5, pp. 786–792, May, 1969.     

Effect of magnetic field on the heat and mass transfer in a vertical annulus

This paper reports the effect of axial or radial magnetic field on the double-diffusive natural convection in a vertical cylindrical annular cavity. The boundary conditions at the side walls are imposed in such a way that the thermal and solutal buoyancy effects are either cooperating or opposing, resulting in a cooperating gradients or opposing gradients flow configuration. The top and bottom walls are insulated and impermeable. The governing equations of this fluid system are solved by the Alternating Direction Implicit and the Successive Line Over Relaxation methods. Total heat and mass transfer rates across the cavity are calculated by evaluating the average Nusselt and Sherwood numbers. The main objective of the present numerical study is to understand the effect of magnetic field on the double-diffusive convection in the annular cavity. From the numerical results, it is found that the magnetic field suppresses the double-diffusive convection only for small buoyancy ratios. But, for larger buoyancy ratio, the magnetic field is effective in suppressing the thermal convective flow. Further, the magnetic field is effective when it is applied perpendicular to the main flow.     

Effect of a magnetic field on ionizing electric discharge in air

We have studied the effect of an external magnetic field on the form and structure of high-voltage gas discharge used for the ionization of airflow to the degree (∼10⁻⁵) necessary for the creation of a magnetohydrodynamic (MHD) control system. The experimental setup based on a shock tube comprised a magnetic field generation system, a 2–4 μs-pulsed, high-voltage, ionizing discharge system and an expanding MHD channel with a set of electrodes oriented along and across the magnetic field. In the first series of experiments, the discharge current was closed along the magnetic field lines; in the second series, the current was closed in the transverse direction. The patterns of discharge glow at various values of the magnetic induction were monitored. It is established that the most effective configuration employs periodic pulsed ionizing discharge in the transverse direction and a system of electrodes closing the magnetic-field-induced current.     

Resistance anomalies in flow of polymer solutions through channels of variable section

An experimental study is performed of developement of elastic turbulence and additional resistance to flows of polymer solutions in channels with periodically varying cross section.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 53, No. 4, pp. 573–579, October, 1987.