Pulsatile flow of thixotropic blood in artery under external body acceleration

This work presents a numerical technique for simulating non-Newtonian blood flow in human's arteries driven by an oscillating pressure gradient. The blood is considered as a thixotropic fluid and its structural properties are considered to obey Moore's thixotropic model as a constitutive equation. The equations of motion are simplified considering the flow laminar, axisymmetric and the fluid incompressible. A numerical solution is presented using finite difference method in order to compute the velocity field and wall shear stress distribution. The numerical results obtained have been validated with the analytical solution available in the literature. Furthermore, the effect of the structural properties, the average of the pressure gradient and the external acceleration on the velocity and wall shear stress distribution is investigated. These results reveal the influence of the different parameters studied on the pipe flow response of the thixotropic fluid.

Bioconvection Due to Gyrotactic Microorganisms in Couple Stress Hybrid Nanofluid Laminar Mixed Convection Incompressible Flow with Magnetic Nanoparticles and Chemical Reaction as Carrier for Targeted Drug Delivery through Porous Stretching Sheet

In this paper, the steady electrically conducting hybrid nanofluid (CuO-Cu/blood) laminar-mixed convection incompressible flow at the stagnation-point with viscous and gyrotactic microorganisms is considered. Additionally, hybrid nanofluid flow over a horizontal porous stretching sheet along with an induced magnetic field and external magnetic field effectsthat can be used in biomedical fields, such as in drug delivery and the flow dynamics of the microcirculatory system. This investigation can also deliver a perfect view about the mass and heat transfer behavior of blood flow in a circulatory system and various hyperthermia treatments such as the treatment of cancer. The simple partial differential equations (PDEs) are converted into a series of dimensional ordinary differential equations (ODEs), which are determined using appropriate similarities variables (HAM). The influence of the suction or injection parameter, mixed convection, Prandtl number, buoyancy ratio parameter, permeability parameter, magnetic parameter, reciprocal magnetic prandtl number, bioconvection Rayleigh number, coupled stress parameter, thermophoretic parameter, Schmidt number, inertial parameter, heat source parameter, and Brownian motion parameter on the concentration, motile microorganisms, velocity, and temperature is outlined, and we study the physical importance of the present problem graphically.

APPLICATION OF DRUG DELIVERY IN MAGNETOHYDRODYNAMICS PERISTALTIC BLOOD FLOW OF NANOFLUID IN A NON-UNIFORM CHANNEL

In this paper, we have studied the application of drug delivery in magnetohydrodynamics (MHD) peristaltic blood flow of nanofluid in a non-uniform channel. The governing equation of motion and nanoparticles are modeled under the consideration of creeping flow and long wavelength. The resulting non-linear coupled differential equation is solved with the help of perturbation. Numerical Integration has been used to obtain the results for pressure rise and friction forces. The impact of various pertinent parameters on temperature profile, concentration profile such as density Grashof number, thermal Grashof number, Brownian motion parameter, thermophoresis parameter and MHD is demonstrated mathematically and graphically. The present analysis is also applicable for three-dimensional profile.

THE INFLUENCES OF CARDIOVASCULAR PROPERTIES ON SUPRASYSTOLIC BRACHIAL CUFF WAVE STUDIED BY A SIMPLE ARTERIAL-TREE MODEL

It has been found that a pronounced secondary systolic peak appears on the oscillometric wave recorded by a brachial oscillometric cuff as cuff pressure is raised to a suprasystolic level. This finding has accordingly motivated some studies aimed to explore the potential value carried by the cuff wave for assessing arterial stiffness. However, so far, there remain considerable controversies in the literature regarding the cardiovascular properties that dominate the characteristics of the cuff wave. In this context, we developed a simple arterial-tree model and applied it to investigate the respective influence on the cuff wave of various cardiovascular properties and the associated wave interaction phenomena. It was found that (1) neither aortic stiffness nor brachial arterial stiffness can uniquely determine the time lag (Δt) between the first and secondary peaks of the cuff wave, although both of them significantly influence Δt; and (2) the BAIx (an index that characterize the height of the secondary peak relative to the first) is sensitive to most of the investigated cardiovascular properties and physiological conditions, such as arterial stiffness, intensity of wave reflection in the lower body and heart rate, etc. These findings suggest that the reliability of assessing aortic stiffness based solely on the timings and heights of the two peaks is limited. Moreover, we argued that the controversial findings presented in previous model-based studies are likely to be caused by limitations related to the research objectives or computation conditions of the studies.

AN IMPROVED MODEL FOR REDUCED-ORDER PHYSIOLOGICAL FLUID FLOWS

An improved one-dimensional mathematical model based on the Pulsed Flow Equations (PFE) is derived by integrating the axial component of the momentum equation over the transient Womersley velocity profile, providing a dynamic momentum equation whose coefficients are smoothly varying functions of the spatial variable. The resulting momentum equation along with the continuity equation and pressure-area relation form our reduced-order model for physiological fluid flows in one dimension and are aimed at providing accurate and fast-to-compute global models for physiological systems represented as networks of quasi one-dimensional fluid flows. The consequent nonlinear coupled system of equations is solved by the Lax-Wendroff scheme and is then applied to an open model arterial network of the human vascular system containing the largest 55 arteries. The proposed model with functional coefficients is compared with current classical one-dimensional theories which assume steady state Hagen-Poiseuille velocity profiles, either parabolic or plug-like, throughout the whole arterial tree. The effects of the nonlinear term in the momentum equation and different strategies for bifurcation points in the network, as well as the various lumped parameter outflow boundary conditions for distal terminal points are also analyzed. The results show that the proposed model can be used as an efficient tool for investigating the dynamics of reduced-order models of flows in physiological systems and would, in particular, be a good candidate for the one-dimensional, system-level component of geometric multiscale models of physiological systems.

EFFECT OF HARMONIC BOUNDARY MOTION ON VELOCITY PROFILE AND SHEAR STRESS OF CONVEYED FLUID IN AN ANNULAR PIPE

In this study, the mathematical model of oscillating flow in an annular straight pipe due to an imposed oscillating pressure gradient and with harmonic boundary motion is established. So far, no literature is devoted to investigate the effect of harmonic boundary motion on the velocity profile and shear stress. The Navier–Stokes Equation in the cylindrical coordinate is the governing equation of fluid motion. The exact solution of this system in terms of real function only is presented. This method is more understood and helpful for deeply investigating the internal oscillating flow than the conventional complex method presented by Womersley. It is found that the effects of the boundary motion, the wave frequency, the Womersley number, and the radius ratio on the velocity profile and shear stress distribution are significant.