Numerical study of biofluid flow over a backward-facing step: The hydro-thermal behavior in the presence of magnetic field effects

2016 ◽  
Vol 231 (4) ◽  
pp. 800-812
Author(s):  
M Mohammadpourfard ◽  
F Ghaderi
Keyword(s):  
Magnetic Field ◽  
Shear Stress ◽  
Magnetic Fields ◽  
Wall Shear Stress ◽  
Thermal Behavior ◽  
Numerical Study ◽  
Control Volume ◽  
Flow Simulation ◽  
Magnetic Field Effects ◽  
Wall Shear

In this paper, the results of adding nanoparticles and applying non-uniform magnetic fields on a biofluid (blood) flow through a two-dimensional horizontal channel with a step are reported. Two magnetic fields with positive and negative gradients were applied. The control volume technique and two-phase mixture model in the numerical approach have been used to illustrate the hydro-thermal behavior of flow. Simulation results reveal that nanoparticles can significantly increase the Nusselt number and wall shear stress. Also, the wall shear stress, Nu, and recirculation length in the presence of a magnetic field with different gradients can be externally controlled. Based on the results, the negative gradient magnetic field increases wall shear stress and Nu in the affected region, unlike the positive gradient.

The influence of magnetic field on wall shear stress in power law fluid flow of blood

2021 ◽  
Author(s):  
Amira Husni Talib ◽  
Ilyani Abdullah ◽  
Nik Nabilah Nik Mohd Naser
Keyword(s):  
Magnetic Field ◽  
Shear Stress ◽  
Fluid Flow ◽  
Wall Shear Stress ◽  
Power Law ◽  
Power Law Fluid ◽  
Wall Shear

Numerical study of flow fields in an airway closure model

2011 ◽  
Vol 677 ◽  
pp. 483-502 ◽  
Author(s):  
C.-F. TAI ◽  
S. BIAN ◽  
D. HALPERN ◽  
Y. ZHENG ◽  
M. FILOCHE ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Normal Stress ◽  
Numerical Study ◽  
Stress Gradient ◽  
Fluid Motion ◽  
Flow Fields ◽  
Airway Epithelial Cells ◽  
Airway Epithelial ◽  
Wall Shear

The liquid lining in small human airways can become unstable and form liquid plugs that close off the airways. Direct numerical simulations are carried out on an airway model to study this airway instability and the flow-induced stresses on the airway walls. The equations governing the fluid motion and the interfacial boundary conditions are solved using the finite-volume method coupled with the sharp interface method for the free surface. The dynamics of the closure process is simulated for a viscous Newtonian film with constant surface tension and a passive core gas phase. In addition, a special case is examined that considers the core dynamics so that comparisons can be made with the experiments of Bian et al. (J. Fluid Mech., vol. 647, 2010, p. 391). The computed flow fields and stress distributions are consistent with the experimental findings. Within the short time span of the closure process, there are large fluctuations in the wall shear stress. Furthermore, dramatic velocity changes in the film during closure indicate a steep normal stress gradient on the airway wall. The computational results show that the wall shear stress, normal stress and their gradients during closure can be high enough to injure airway epithelial cells.

Numerical Study on Flow-Adaptive Stents

2008 ◽  
Vol 33-37 ◽  
pp. 1031-1036
Author(s):  
Yoko Takakura ◽  
Gulbahar Wahap ◽  
Norio Arai ◽  
Yoshifumi Konishi ◽  
Kazuaki Fukasaku
Keyword(s):  
Shear Stress ◽  
Shear Rate ◽  
Wall Shear Stress ◽  
Fluid Mechanics ◽  
Endovascular Therapy ◽  
Numerical Study ◽  
Two Dimensional ◽  
Numerical Computations ◽  
Wall Shear ◽  
Two Dimensional Flows

Recently for the treatment of aneurysms, endovascular therapy with microcoils and stents has started. This study explores the design of better stents by means of numerical computations from the viewpoint of the fluid mechanics. Two-dimensional flows are numerically solved for a stented duct with a model of an aneurysmal sac by changing the distribution of stent filaments under the constraint of a constant porosity for the neck. Stents are assessed by whether the wall shear stress (WSS) on the aneurismal wall and the shear rate (SR) within the aneurysm are made lower. Barometers for the allocation of filaments are sought, and resultant optimized stents are those where filament(s) should be attached to both the distal and proximal wall of the neck, with more filaments to the distal wall, to make the WSS low, and filaments should be appropriately distributed in the off-wall portion of the neck to make the SR low.

scholarly journals Analysis of Flow Characteristics of the Blood Flowing through an Inclined Tapered Porous Artery with Mild Stenosis under the Influence of an Inclined Magnetic Field

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Neetu Srivastava
Keyword(s):  
Magnetic Field ◽  
Blood Flow ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Flow Rate ◽  
Flow Characteristics ◽  
Volumetric Flow Rate ◽  
Mhd Equations ◽  
Inclined Magnetic Field ◽  
Wall Shear

Analytical investigation of MHD blood flow in a porous inclined stenotic artery under the influence of the inclined magnetic field has been done. Blood is considered as an electrically conducting Newtonian fluid. The physics of the problem is described by the usual MHD equations along with appropriate boundary conditions. The flow governing equations are finally transformed to nonhomogeneous second-order ordinary differential equations. This model is consistent with the principles of magnetohydrodynamics. Analytical expressions for the velocity profile, volumetric flow rate, wall shear stress, and pressure gradient have been derived. Blood flow characteristics are computed for a specific set of values of the different parameters involved in the model analysis and are presented graphically. Some of the obtained results show that the flow patterns in converging region (ξ<0), diverging region (ξ>0), and nontapered region (ξ=0) are effectively influenced by the presence of magnetic field and change in inclination of artery as well as magnetic field. There is also a significant effect of permeability on the wall shear stress as well as volumetric flow rate.

EFFECTS OF TRANSVERSE MAGNETIC FIELD ON THE PERISTALTIC TRANSPORT OF VISCOELASTIC FLUID WITH JEFFREY MODEL IN A FINITE LENGTH CHANNEL

2011 ◽  
Vol 25 (26) ◽  
pp. 3455-3471 ◽  
Author(s):  
D. TRIPATHI ◽  
T. HAYAT ◽  
N. ALI ◽  
S. K. PANDEY
Keyword(s):  
Magnetic Field ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Viscoelastic Fluid ◽  
Transverse Magnetic Field ◽  
Flow Rate ◽  
Volume Flow Rate ◽  
Transverse Magnetic ◽  
Volume Flow ◽  
Wall Shear

This paper investigates the peristaltic flow of viscoelastic fluid represented by Jeffrey model in presence of transverse magnetic field under long wavelength and low Reynolds number assumptions. The expressions of pressure gradient, volume flow rate, average volume flow rate and local wall shear stress are obtained. The effects of transverse magnetic field, electrical conductivity (i.e., Hartman number M), relaxation time and retardation time on pressure difference, local wall shear stress, and mechanical efficiency of peristaltic pump are discussed. Reflux limit for viscoelastic fluid is also found and the effects of all parameters on reflux phenomena are discussed. Comparative study of integral and nonintegral number of waves propagate in a train is presented.

scholarly journals Numerical Study of Non-Newtonian Blood Behavior in the Abdominal Aortic Bifurcation of a Patient-Specific at Rest

2017 ◽  
Vol 10 (1) ◽  
pp. 279-285 ◽  
Author(s):  
Carlos Oliveira ◽  
Armando A. Soares ◽  
André Simões ◽  
Sílvia Gonzaga ◽  
Abel Rouboa
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Cardiovascular Health ◽  
Numerical Study ◽  
Shear Thinning ◽  
Patient Specific ◽  
Aortic Bifurcation ◽  
Low Velocity ◽  
Abdominal Aortic ◽  
Wall Shear

Background:The interaction of blood flow with walls of blood vessels is central for the development and maintenance of cardiovascular health. The analysis of wall shear stress is, therefore, fundamental in hemodynamic studies.Objective:The aim of this work is to study numerically the influence of the shear thinning blood properties on the hemodynamics in the abdominal aortic bifurcation for a patient-specific at rest.Methods:Were tested two models for the blood dynamic viscosity, one Newtonian and other non-Newtonian, with dependence on hematocrit and total protein minus albumin.Results and Conclusion:The results show the shear thinning behavior influence on the velocity distribution and wall shear stress. Furthermore, wall shear stress values are globally lower for non-Newtonian blood model at high velocity values than those for the Newtonian blood model. However, for low velocity values this behavior is inverted.

Effects of transmural pressure and wall shear stress on LDL accumulation in the arterial wall: a numerical study using a multilayered model

2007 ◽  
Vol 292 (6) ◽  
pp. H3148-H3157 ◽  
Author(s):  
Nanfeng Sun ◽  
Nigel B. Wood ◽  
Alun D. Hughes ◽  
Simon A. M. Thom ◽  
X. Yun Xu
Keyword(s):  
Experimental Data ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Arterial Wall ◽  
Numerical Study ◽  
Transmural Pressure ◽  
Diffusion Reaction ◽  
Model Parameters ◽  
Optimization Approach ◽  
Wall Shear

The accumulation of low-density lipoprotein (LDL) is recognized as one of the main contributors in atherogenesis. Mathematical models have been constructed to simulate mass transport in large arteries and the consequent lipid accumulation in the arterial wall. The objective of this study was to investigate the influences of wall shear stress and transmural pressure on LDL accumulation in the arterial wall by a multilayered, coupled lumen-wall model. The model employs the Navier-Stokes equations and Darcy's Law for fluid dynamics, convection-diffusion-reaction equations for mass balance, and Kedem-Katchalsky equations for interfacial coupling. To determine physiologically realistic model parameters, an optimization approach that searches optimal parameters based on experimental data was developed. Two sets of model parameters corresponding to different transmural pressures were found by the optimization approach using experimental data in the literature. Furthermore, a shear-dependent hydraulic conductivity relation reported previously was adopted. The integrated multilayered model was applied to an axisymmetric stenosis simulating an idealized, mildly stenosed coronary artery. The results show that low wall shear stress leads to focal LDL accumulation by weakening the convective clearance effect of transmural flow, whereas high transmural pressure, associated with hypertension, leads to global elevation of LDL concentration in the arterial wall by facilitating the passage of LDL through wall layers.

scholarly journals Mathematical Modelling of Blood Flow through a Tapered Overlapping Stenosed Artery with Variable Viscosity

2014 ◽  
Vol 11 (4) ◽  
pp. 185-195 ◽  
Author(s):  
G. C. Shit ◽  
M. Roy ◽  
A. Sinha
Keyword(s):  
Magnetic Field ◽  
Blood Flow ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Pressure Gradient ◽  
Variable Viscosity ◽  
Stenosed Artery ◽  
Flow Through ◽  
Wall Shear ◽  
Analytical Expressions

This paper presents a theoretical study of blood flow through a tapered and overlapping stenosed artery under the action of an externally applied magnetic field. The fluid (blood) medium is assumed to be porous in nature. The variable viscosity of blood depending on hematocrit (percentage volume of erythrocytes) is taken into account in order to improve resemblance to the real situation. The governing equation for laminar, incompressible and Newtonian fluid subject to the boundary conditions is solved by using a well known Frobenius method. The analytical expressions for velocity component, volumetric flow rate, wall shear stress and pressure gradient are obtained. The numerical values are extracted from these analytical expressions and are presented graphically. It is observed that the influence of hematocrit, magnetic field and the shape of artery have important impact on the velocity profile, pressure gradient and wall shear stress. Moreover, the effect of primary stenosis on the secondary one has been significantly observed.

Numerical Study of Flow Dynamics in Human Eye Vitreous Chamber After Vitrectomy and Gas Tamponade

2015 ◽  
Author(s):  
Ali Yousefi ◽  
Omid Abouali ◽  
Ebrahim Ghoshtasbi Rad ◽  
Goodarz Ahmadi
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Two Phase Flow ◽  
Numerical Study ◽  
Maximum Shear Stress ◽  
Phase Flow ◽  
Two Phase ◽  
Human Eye ◽  
Gas Tamponade ◽  
Wall Shear

The purpose of this study is to evaluate the flow pattern and the fluid shear stress acting on the retinal wall in a human eye vitreous chamber after Vitrectomy and gas tamponade including the effect of saccadic eye movements. The correlation between the maximum shear stress induced on the retinal wall and the gas fill fraction (GF) and saccade amplitudes was investigated. In modeling the geometry of vitreous chamber cavity, the indentation of the lens was taken into account. The two-phase flow at the recovery phase of the operation was modeled numerically. Unsteady three-dimensional forms of continuity and Navier-Stokes equations were solved. Volume-of-fluid method was used to solve the two-phase flow in the eye. Saccadic motion of the eye was modeled using the dynamic mesh technique. The numerical model was validated by comparing the results with the available analytical solutions and experimental data for a spherical model. Then, numerical simulation was performed based on the deformed sphere configuration, representing a more realistic model of vitreous chamber cavity. The simulation results were compared with the available numerical studies for the spherical geometry. Then the wall shear stress on the retina was computed and compared for various gas fractions. The potential effect of wall shear stress on the retinal detachment and the need for post-operation posturing in all studied cases were discussed.

Sign in / Sign up

Export Citation Format

Share Document