An evaluation of a micropolar model for blood flow through an idealized stenosis

Cross-diffusive flow of MHD micropolar nanofluid past a slip stretching plate

As a novel fluid of functional material, magnetohydrodynamic (MHD) micropolar fluid has the special properties of light, heat, magnetic and so on. It is of highly practical significance. The characteristics of flow, heat and mass transfer in MHD micropolar nanofluid boundary layer past a stretching plate are investigated based on the micropolar fluid theory in the present numerical work. In the presence of magnetic field, viscous dissipation and the cross-diffusion caused by Dufour effect and Soret effect are considered. First order slip velocity condition is employed. Mathematical models are built based on the assumptions. Collocation spectral method (CSM) via matrix multiplication is adopted to solve the two-dimensional dimensionless nonlinear partial governing equations. The program codes based on CSM is developed, validated and employed. The coupled effects of microrotation, Dufour effect, Soret effect, magnetic field as well as first order slip velocity boundary condition on the flow, heat and mass transfer are revealed. Besides, the variation trends of local Nusselt number and Sherwood number are analyzed in detail. The numerical results indicate that the fluid flow can be suppressed obviously in the consideration n of slip condition and magnetic field. As slip parameter δ and magnetic parameter M rise, the velocity in the boundary layer becomes lower gradually; further, both temperature and concentration increase. On the other hand, the opposite trend can be noticed with the effect of material parameter K . Moreover, E c and D f augment the temperature; while, S r leads to an upsurge in concentration. The temperature rises by about 79.73 % with Dufour effect and S h enlarges by a factor of about 38.15 % with Soret effect. The concentration boundary layer decreases by about 37.50% is when K = 5.0 .

Non-Newtonian pulsatile blood flow through the stenosed arteries: comparison between the viscoelastic and elastic arterial wall in response to the alterations

In this study, we investigate the impact of aortic stenosis on the hemodynamics of pulsatile blood flow within a 3D aortic model. Employing a non-Newtonian Casson model with a hematocrit of 45%, our study introduces a preliminary hypothesis to simulate blood flow dynamics, incorporating both linear elastic and viscoelastic models to define the mechanical characteristics of the artery. Through simulations conducted with Ansys-Cfx (version 15), we utilize a 2-way fluid-structure interaction (FSI) approach, employing a Lagrangian-Eulerian formulation with second-order accuracy. We explore the influence of stenosis severity on variables including velocity profiles, pressure distribution, shear stress, wall displacement, and changes in the OSI parameter. Our investigation encompasses arteries with both elastic and viscoelastic walls. The key findings that arise from our results highlight the viscoelastic model's demonstration of reduced radial wall displacement when compared to the linear elastic model. Additionally, we observe that elevated arterial stenosis percentages lead to the elongation of vortex length, heightened wall shear stress, and increased slope of velocity profiles downstream of the stenosed region. Furthermore, bulky obstruction of viscoelastic arteries as opposed to elastic, resulted in a maximum 5 percent increase in velocity profile and a 29.6% decrease in radial displacement. The zenith of shear stress occurs concomitantly with the velocity's peak within the stenosed area. Viscoelastic arterial wall shear stress at the stenosis site escalates due to the rapid expansion of the stenosis. The viscoelastic wall, responding with a blend of viscous and elastic characteristics to applied stress, undergoes slight deformation in shape. Following stress reduction, the wall gradually reverts to its original form, thus alleviating some of the applied stress. In contrast, the elastic wall retains its altered shape due to stress preservation within the material. Additionally, we ascertain an augmentation in radial displacement corresponding with increased artery stenosis.

Rotational Particle Separation in Solutions: Micropolar Fluid Theory Approach

We develop a new mathematical model for rotational sedimentation of particles for steady flows of a viscoplastic granular fluid in a concentric-cylinder Couette geometry when rotation of the Couette cell inner cylinder is prescribed. We treat the suspension as a micro-polar fluid. The model is validated by comparison with known data of measurement. Within the proposed theory, we prove that sedimentation occurs due to particles' rotation and rotational diffusion.

Effect of Micropolar Fluid Properties on the Blood Flow in a Human Carotid Model

Blood is a non-homogeneous fluid that flows inside the human artery system and provides the cells with nutrients. In this study the auto rotation effect of blood’s microstructure on its flow inside a human carotid model is studied by using a micropolar fluid model. The study aims to investigate the flow differences that occur due to its microstructure as compared to a Newtonian fluid. We focus on the vortex viscosity effect, i.e., the ratio of microrotation viscosity to the total one, because this is the only parameter that affects directly the fluid flow. Simulations in a range of vortex viscosities, are carried out in a 3D human carotid model that is computationally reconstructed. All of the simulations are conducted at the diastolic Reynolds number that occurs in the human carotid. Results indicate that micropolarity affects blood velocity in the range of parameters studied by 4%. As micropolarity is increased, higher velocities in the center of vessels and lower near the boundaries are found as compared to a Newtonian fluid consideration. This is an indication that the increase of the fluid’s micropolarity leads to an increase of the boundary layer thickness. More importantly, an increase in vortex viscosity and the resulting increase in microrotation result in decreased shear stress in the carotid’s walls; this finding can be significant in regards to the onset and the development of atherosclerosis. Finally, the flow distribution at the carotid seems to heavily be affected by the geometry and the micropolarity of the fluid.

Metallic nanoparticles analysis for the blood flow in tapered stenosed arteries: Application in nanomedicines

Blood flow model is recycled to study the influence of magnetic field and nanoparticles in tapered stenosed arteries. The metallic nanoparticles for the blood flow with water as base fluid are not explored so far. The representation for the blood flow is through an axially non-symmetrical but radially symmetric stenosis. Symmetry of the distribution of the wall shearing stress and resistive impedance and their growth with the developing stenosis is another important feature of our analysis. Exact solutions have been evaluated for velocity, resistance impedance, wall shear stress and shearing stress at the stenosis throat. The graphical results of different types of tapered arteries (i.e. converging tapering, diverging tapering, non-tapered artery) have been examined for different parameters of interest for pure water and Copper water ( Cu -water).

Comparison of physiological and simple pulsatile flows through stenosed arteries

Most experimental and numerical studies of pulsatile flow through stenosed arteries have been performed for a first harmonic oscillatory flow. In this paper, numerical solutions are presented for a physiological pulsatile flow as well as for an equivalent simple pulsatile flow, having the same stroke volume as the physiological flow, and the differences in their flow behavior are discussed. The analysis is restricted to laminar flow, Newtonian fluid and axisymmetric rigid stenosis. Comparison of results shows that the behaviors of the two flows are similar at some instances of time, however, important observed differences indicate that for thorough understanding of pulsatile flow behavior in stenosed arteries, the actual physiological flow should be simulated.