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The theoretical blood flow velocity profile in the aorta for four specimens is modelled for Womersley numbers in the range of 10, taking into account the viscous effect. Blood arteries of various diameters from humans, dogs, rabbits, and mice were chosen. The flow domain shows a pulsatile wave as a single straight tube with a rigid wall that is propagating at infinite wave speed. A linear second-order PDE with pressure amplitude as a forcing function is created using the Navier- Stokes equations. The resulting general equation is a Bessel differential equation with complex arguments and Zeroth-order Bessel functions. Using the proper boundary conditions, the velocity profile and related shear stress were determined. The impact of the velocity profile and Womersley number on pulsatile flow was identified for a range of forcing functions. [ABSTRACT FROM AUTHOR]

In this paper we study the Klein-Gordon equation with two variable coefficients nonlinearities. We investigate energy negative, energy subcritical and energy supercritical cases and derive sufficient conditions for finite time blow up of the weak solutions to the Cauchy problem. [ABSTRACT FROM AUTHOR]

In agricultural machinery, most especially, the rotary elements are powered by the tractor take-off shaft (PTO). Due to excessive impact loading, the PTO shaft experiences high dynamic loading during this operation. Consequently, there is a possibility that the PTO shaft will fail during operation. A study like this will help to understand more about the behavior of the PTO shaft and provide manufacturers with valuable information on how to improve the fatigue life of the shaft using FEA tools. Research and development of new products can be made more cost-effective by implementing this technology. Using analytical approach, Von-mises stress is found to be 4123.14 PSI, which is nearly the same for FEA (4083.7 PSI) with a difference of 10% between the results, which is within an acceptable range. Additionally, the maximum shear stress value when it is calculated numerically is 22453.18 PSI, close to the maximum shear stress value when it is calculated by FEA (16155.8). [ABSTRACT FROM AUTHOR]

The problem of hemodynamics in a coronary vessel with stenosis is considered, taking into account different boundary conditions on the vessel wall. Two types of conditions are considered: no-slip and slip. The blood model is considered as a non-Newtonian fluid, the viscosity of which is determined using the Carreau model. It is shown that changing the boundary conditions on the slip entails changing the confined fluid flow which leads to significant changes in the hemodynamic pattern throughout the stenosis area up to atypical in-vivo observations. Thus, the choice of the slip boundary condition on the vessel wall,as well as the details of the flow in the near-wall layer, is a key factor in obtaining reasonable results. [ABSTRACT FROM AUTHOR]

Blood flow through arteries of varied diameters was numerically studied. Three radius (1mm, 1.5mm, 2mm) and length (50m) cases are studied in this project, with Reynolds numbers of laminar flows ranging from 50,100,150,200 based on previous studies, and temperatures set at 298 K° to apply thermal boundary flux of q =100 w/m², q =300 w/ m², q=500 w/ m², and q =700 w/ m², respectively. The results displayed that all data have been same patterns as rise temperature blood towards the exit where blood temperature rises as the distance from the artery's input region grows in the x-direction. Effects of Reynolds number on temperature distribution of blood clearly seen in all cases where rising Reynolds number leads to decrease in temperature of blood flow due to increase flow rate of blood. The maximum temperature of blood fluid flow was found at Reynolds number 50 in each case. Furthermore, a counter of temperature distribution of blood flow is presented, which proved that the temperature distribution of blood flow is gradually increasing towards the exit. Increased Reynolds number, on the other hand, leads to a rise in Nusselt number of blood fluid flow due to increased blood flow rate. In general, the Nu of blood fluid flow has observed the same patterns in all cases, resulting in linear reductions in values across the Reynolds number range with a heat flux of 700 W/ m² These findings show that any medical dealing, including serum injections, blood thinners, and all drugs, can be affected by changes in blood flow due to increased or decreased blood flow rate or temperature. It can be seen that increase heat flux leads to rises in axial Nu of blood fluid flow and the maximum axial Nu of blood fluid flow occurred with heat flux of 700 W/ m² in compared with other cases due to increase heat convection in blood flow. Compares the axial Nu of blood fluid flow for three cases are investigated in this study, with case 1 (r=0.001) having the highest axial Nu of blood fluid flow in contrast to the other cases due to the small size of the artery leading to increased blood flow rate in the artery. [ABSTRACT FROM AUTHOR]

This paper provides an analytic solution of the electroosmotic flow of Maxwell fluid of an electroneutral solute through a polyelectrolyte layer (PEL) covered concentric cylindrical annulus in the presence of an applied alternating current electric field. PEL has a positive charge density and a uniform thickness. The ionic species follows the modified Boltzmann distribution at a low surface charge and using Debye-Hückel approximation the solution of induced potential is obtained by solving the linearized Poisson-Boltzmann equation inside and outside the PEL. The expressions for the axial velocity profile are determined by solving the modified Cauchy momentum equation along with the shear stress-shear rate relationship of Maxwell fluid. The modified Bessel function formulation is used to evaluate the analytic solutions. The wall zeta potentials of the cylindrical annulus can be symmetric or asymmetric. The objective of this study is to examine the effects of the dimensionless parameters such as bulk ionic concentration, oscillating Reynolds number, PEL fixed charge density, relaxation time, the ratio of the wall zeta potential, and softness parameter which arise in the governing dimensionless equations. For both Newtonian and Maxwell fluids, the axial velocity increases with the ionic concentration of the electrolyte solution but decreases with the fixed positive charge density in the PEL. With the higher value of the softness parameter, the velocity profile declines. The axial velocity rise as the relaxation time increases. The flow oscillations increases but velocity amplitude decreases with the higher values of the oscillating Reynolds number. [ABSTRACT FROM AUTHOR]

This paper presents a numerical method for two-fluid flows with phase change phenomenon. The motion of interface is captured using volume of fluid (VOF) method along with a geometrical reconstruction method called PLIC. Interfacial source terms for surface tension, heat and mass transfers are modelled and integrated with the governing equations of VOF model available in commercial CFD software, ANSYS- Fluent, using user-defined functions (UDFs). The model is used to simulate a film boiling problem where vapor bubbles are emanating from the film covering a heated wall. The effects of heated wall profile modification and the degree of superheat on transient vapour bubble evolution are analysed in details. It is found that an increase in heated wall surface area or degree of superheat enhances the vapour bubble formation and emission significantly. It is evident from the simulations that the combined effect is possible when these parameters are increased together. These enhancement techniques have proved to reduce the time difference between two consecutive bubble rises from the thin film covered the heated wall surfaces. [ABSTRACT FROM AUTHOR]

Atherosclerosis has become one of the most common health problems in today's lifestyle. Our focus is on Coronary Artery Stenosis. Coronary Artery Stenosis is caused by narrowing of arteries, when there is formation of plaque on the walls of Coronary Artery. If not diagnosed at the early stage, the blockage could advance and might lead to stroke or even death. To diagnose the severity of stenosis, Fractional flow Reserve (FFR) value is taken into consideration. FFR value represents the amount of flow that could be achieved despite the presence of stenosis in the artery. Traditionally, FFR is measured using a specialized probe inserted through a catheter tube, and the technique is expensive. In our proposed work we tend to compute the FFR value through the non-invasive method by utilizing Computational Fluid Dynamics (CFD). FFR value could be calculated by the ratio of distal and proximal pressures to the stenosis. Improved Diagnostic Accuracy can be obtained by using the Computational Fluid Dynamics method. This could help the physician determine whether the patient requires angioplasty or not. As the proposed measurement is by non-invasive method, the patient can avoid Coronary Angiogram which is a painstaking process [ABSTRACT FROM AUTHOR]

A study on blood flow through a stenotic provides a better understanding of the physiology and challenges faced in the treatment of atherosclerosis. The shape, length and height of the stenosis in an artery under various flow conditions play a pivotal role. Research has been carried out by many researchers on the nature of geometry of the stenosis in the artery, nature of the blood and its flow. The results related to the various flow properties such as wall shear stress, velocity, pressure breakdown, flow velocity and resistance are found by many researchers. This paper presents a review on the geometry and methods of solving the model under various conditions. [ABSTRACT FROM AUTHOR]

The swirling blood flow in cardiovascular system has both beneficial and detrimental effects on hemodynamic parameters. A numerical investigation has been performed in a model stenosed artery to analyse the effects of swirling in non-Newtonian pulsatile blood flow through arterial stenosis. The standard k-ω turbulent model is used for the simulation of pulsatile blood flow with swirling. In this investigation, the Reynolds number varies from 200 to 1000. The wall shear stress, hydrostatic pressure and centreline velocity patterns at different time steps are obtained to compare the swirling effect with no swirl condition. Wall shear stress and hydrostatic pressure are not affected by swirling. The streamline contours show that swirling causes substantial variation in velocity distribution. The massive turbulence near the wall is observed in post stenotic region as a dominant effect of swirling. The effect of pulsatile swirl flow is discussed with the relevant pathological conditions. [ABSTRACT FROM AUTHOR]

Biomagnetic fluid dynamics (BFD) is an important application in medical sciences and bioengineering research. Due to this, biomagnetic fluid flow through a stenosed bifurcated artery is numerically studied. A biomagnetic fluid can be found in a living creature and its flow is influenced by the present of a magnetic field. Blood is a typical biomagnetic fluid due to the interaction of intercellular protein, cell membrane and the haemoglobin. This study considered the flow to be incompressible, laminar, two-dimensional (2D), fully developed viscous flow of a Newtonian biomagnetic fluid (blood) in a stenosed bifurcated artery under the effect of a spatially varying magnetic field. A simplified mathematical model of BFD was developed only for isothermal case. Numerical results are obtained using COMSOL Multiphysics 5.2 based on finite element method (FEM). Results concerning the different values of magnetic field intensity produce a considerable effect on the blood flow characteristics such as the velocity profiles and the streamlines patterns. It is shown that the vortex at lower wall extends vertically while vortex at upper wall becomes shrink as the magnetic field strength increases. The location of the magnetic source also can affect the velocity at the daughter artery where the velocity at the lower wall of daughter artery is lower than the upper wall. [ABSTRACT FROM AUTHOR]

Unsteady blood flow characterized by micropolar fluid in a stenosed artery under the influence of a uniform magnetic field is considered. The governing equations in the cylindrical coordinate system are discretized and solved using the Marker and Cell (MAC) method, where the pressure is calculated iteratively using the Successive-Over-Relaxation (SOR) method. The outcomes are tested for numerical stability with desired degree of accuracy. The results carried out include the flow-field profiles of blood, the wall shear stress and the streamlines. The results also predict the pressure drop across the multiple stenoses and show that the pressure drop gets the highest value when it crosses both stenoses. Blood flow contours have been plotted to understand the flow pattern in the diseased artery, which alters significantly in the downstream of the stenosis in the presence of a magnetic field. [ABSTRACT FROM AUTHOR]

The current study presents three-dimensional modelling and analysis of blood flow through carotid artery bifurcation in multiple cases hemodynamics modelling of fluid viscosity. The study considered Newtonian and non-Newtonian blood flow models and solved the three-dimensional laminar and steady Naiver-Stokes (NS) equations for different inlet velocity profiles. Two methods were used to define dynamic viscosity the Carreau Yasuda model and power law non-Newtonian. A comparative analysis was carried out for Newtonian and non-Newtonian fluid models under simple pulsatile, equivalent pulsatile and physiological velocity profiles. The non-Newtonian model in Carreau and power law non-Newtonian showed a higher central velocity than the Newtonian model about 10%. The non-Newtonian model showed 80% higher Wall shear stresses, either the pressure results on the arterial wall were similar in all models. [ABSTRACT FROM AUTHOR]

An important area of tissue engineering is the development of small-diameter vascular grafts. In our study we assessed whether an electrospun polymer scaffold is beneficial for developing a tissue-engineered graft. The polymeric grafts were made from a blend of polyhydroxybutyrate/valerate and polycaprolactone (PHBV/PCL) and added type I collagen. Additionally, the grafts were treated with fibronectin. Cells were isolated from the peripheral blood of patients with coronary artery disease (CAD) and then seeded on the luminal graft surface. Then, the grafts with cells were cultured in a pulsatile flow bioreactor. We confirmed that separate feeding of PHBV/PCL and type I collagen during electrospinning allows developing a scaffold for a vascular graft suitable for maintaining the viability of the endothelial layer on the luminal surface. [ABSTRACT FROM AUTHOR]

Cardiovascular diseases are one of the major concerns of the present age. Atherosclerosis, heart blockage, heart failing are very common of them which are caused by plaque formation in the T-and Y-shaped junctions of blood vessels. At the present study concentration has been focused on the studies of pulsatile non-Newtonian flow behavior through Y-junction for unit flow ratio experimentally and numerically. Pulsatile flow similar to external iliac vein has been generated using gear pump. Four pressure sensors have been inserted two at the upstream and two at the downstream points to visualize the pressure condition. 50% (w/w) glycerin-water solution has been selected as working fluid as its density and viscosity are very much similar to blood-matrix. Numerical simulation has been accomplished by Ansys Fluent 14.5 software where Carreau model has been used to characterize the non-Newtonian flow behavior of blood-matrix. X-velocity contour, Z-vorticity contour, pressure wave form and vector plot have been studied in details. Those results can be used to predict the flow behavior through veins and arteries and to detect the recirculation zone. [ABSTRACT FROM AUTHOR]

The desire of the current article is to discover the pulse driven Couette flow of Ag-water based nanofluid restrained between two parallel plates with convective heat exchange with the ambient surrounding at the upper wall beneath the combined effects of thermophoresis, Brownian motion and temperature dependent viscosity. The Buongiorno model is considered to illustrate the current flow analysis effectively. In this analysis, water as the base fluid and silver (Ag) as nanoparticles are exercised. The governing flow equations are generalized with the help of boundary layer approximations. Momentum, energy, and nanoparticle concentration equations are generated numerically using finite difference method. The findings of non-dimensional parameters like Brownian motion parameter, Biot number, viscosity variation parameter, stretching velocity parameter, steady pressure gradient, phase angle, and amplitude are conferred graphically. As a final point, skin friction and Nusselt number are anticipated in numeric form with an excellent agreement. From the achieved outcomes, it is noticed that the velocity is directly proportional to the pulsatile pressure gradient. [ABSTRACT FROM AUTHOR]

A finite element Fluid-Structure-Interaction (FSI) model is developed and validated for hemodynamic pulsatile blood flow through a stenosed artery under the effect of an applied magnetic field. The two-layered blood flow is considered with a core layer of suspension of all erythrocytes assumed to be a non-Newtonian Casson fluid and a peripheral layer of plasma, free from cells, as a Newtonian fluid. The model is considered for the 2D idealized elastic arteries. The blood flow is characterized as a steady, laminar, incompressible and unidirectional flow velocity at the inflow and various values of blood-pressure at the outflow, while the arterial walls as well as the surrounding muscles are modeled as a hyperelastic neo-Hookean material and results are obtained for axial velocities, total flow rate, pressure gradient and wall shear stresses (WSS) and solid displacement due to blood pulse. The result shows significant strengthened WSS at the stenotic regions and weakened WSS at the distal side of stenosis neck. It is found that the increase of stenosis size (height) increases the pressure drop and WSS, whereas velocity and flow rate decreases. The wall deformation and WSS may play an important role in the flow mechanics of blood in the stenotic vessel. It is also observed that the fluid velocity and flow rate were reduced when the magnetic field was introduced as well as when its intensity was increased, while WSS was increased with the increase of Hartmann number (Ha) as well as Reynolds number (Re). This work may enhance to work upon the strength of magnetic field to regulate the blood flow in hypertensive patients and those who have blockage in their arteries. [ABSTRACT FROM AUTHOR]

The mathematical modeling and numerical simulations are expected to play an important role to predict the genesis of different cardiovascular diseases, such as the formation and rupture of aneurysms. In the present work, the numerical solutions of the oscillatory blood flow are constructed for an elastic artery with a model aneurysm by use of the software ANSYS. It is observed that the artery elastic strain behaves in a different way: stably or unstably depending on the different combinations between the flow parameter (outlet pressure) and the elastic modulus of the artery wall. [ABSTRACT FROM AUTHOR]

Total cavopulmonary connection is a blood flow pathway which is created surgically by an operation known as Fontan procedure, performed on children with single ventricle heart defects. Recent studies have shown that the hemodynamics in the connection can be strongly influenced by the presence of pulsatile flow. The aim of this paper is model the pulsatile flow patterns, and to calculate the vorticity field and power losses in an idealized 1.5D offset model of Total Cavopulmonary Connection. A three-dimensional polyhedral mesh was constructed for the numerical simulation. The rheological properties of blood were considered as Newtonian, and flow in the connection was assumed to be laminar. The results demonstrated complex flow patterns in the connection. The outcomes of the simulation showed reasonable agreement with the results available in the literature for a similar model. [ABSTRACT FROM AUTHOR]

Stroke is still one of the leading causes for death after heart diseases and cancer in all over the world. Strokes happen because an artery that carries blood uphill from the heart to the head is clogged. Most of the time, as with heart attacks, the problem is atherosclerosis, hardening of the arteries, calcified buildup of fatty deposits on the vessel wall. In this study, the fluid dynamic simulations were done in a left carotid bifurcation under the pulsatile flow conditions computationally. Pulsatile flow waveform is given in the paper. In vivo geometry and boundary conditions were obtained from a patient who has stenosis located at external carotid artery (ECA) and internal carotid artery (ICA) of his common carotid artery (CCA). The location of critical flow fields such as low wall shear stress (WSS), stagnation regions and separation regions were detected near the highly stenosed region and at branching region. [ABSTRACT FROM AUTHOR]

The importance of regular health monitoring has led to a large variety of medical products being available in the market. Motion artifact is still a limitation in portable optical devices which can provide accurate results. We will address the possibility of measuring a pulsatile flow in a noisy environment using an approach based on speckle dynamics. In specific case we measure pulsation or the heart rate in presence of motion between the illumination and the in-vitro or in-vivo sample. The main motion induced artifact in the signal being measured arises from changing the light penetration depth at various positions being illuminated. These measurements have been compared for different settings and multiple-exposure time of the camera. We compare the result for each measurement based on two techniques of speckle contrast and correlation. Under several parameters of the measurement, different analysis techniques were successful but in general correlation approach shows to be more robust for larger motion induced artifacts. Shorter exposure times provide a more detailed spectrum and more successful for extracting the signal from the induced motion artifact, in case of correlation analysis. The in-vivo measurement results agreed fairly with in-vitro case. [ABSTRACT FROM AUTHOR]

The paper is focused on the experimental investigation of the flow parameters influence (stationary component of flow, frequency, amplitude) on the transition to turbulence in pulsatile flow in a straight square channel. The measurements were performed in water. The wall shear stress (WSS) was measured with the help of Constant Temperature Anemometry (CTA) method using a hot-film flush mounted probe. At the same time the pressure drop was measured using the pressure sensors. The pulsatile flow was generated by superposition of the stationary and oscillatory flow components. [ABSTRACT FROM AUTHOR]

The article analyzes the results of numerical simulations of pulsatile flow in a square channel with a 90° bend using Proper Orthogonal Decomposition (POD). The simulations of laminar steady and unsteady flow obtained by ANS YS Fluent commercial system were used as input for modal decomposition. Several regimes for different values of individual parameters (stationary flow component,) were simulated. Not only energy-related modes but also modes significant from the viewpoint of energy dissipation. Other evaluated modes are the modes corresponding to the pulsatile flow frequency and the modes reflecting the flow separation at the bend. [ABSTRACT FROM AUTHOR]

Experiment on two-phase pulsatile flow in a narrow rectangular visualization channel was carried out and photographed. Every frame was treated and restored as a black-white binary picture with the threshold of both gray-scale and gray-scale gradient. The gas-liquid interface in the binary pictures can be recognized well, including some very obvious interface, which either cannot be distinguished, or introduce big wrong-recognized area with the gray-scale threshold only. Then after such as 'dilate', 'erode', 'fill', 'filter' and so on operating, the binary pictures can reflect the twophase distinction situation in the experimental channel well; The instantaneous average void frictions at the length that the camera covered were calculated by counting the black and white pixels from the pictures. The average void fractions in the whole length of the test section were calculated with an iteration method. The average void fractions in the special length covered by camera and the ones in the whole length of the test section are different. The former shows that the void frictions dramatically frequently change, while the later at steady flow almost stay peace, at pulsatile flow change smoothly. [ABSTRACT FROM AUTHOR]

In a blood vessel, the main scatterers of Ultrasound (US) waves are the red blood cells (RBCs) and their aggregation. The depletion model proposes RBC aggregation formed from osmotic attractive forces due to polymer depletion, which overcome electrostatic repulsion due to RBC surface charge. Previous studies of simulation model under steady flow elucidated the relationship between shear rate and RBC aggregation. But shear rate could not fully explain the cyclic variation of backscattered power from blood under pulsatile flow. In the current study, a two-dimensional particle model capable of RBC mimicking the main characteristics of RBC aggregation kinetics was proposed to elucidate the relationship between microscopic RBC interactions and macroscopic rheological behavior. The mechanical model of RBCs is a depletion model under pulsatile flow. There are 596 RBCs randomly placed in a vessel (0.1X1mm) in the model driven by hydrodynamic force, aggregation force and elastic force. The mean flow velocity at the center of the tube was 2cm/s with the variation 0.5∼1.5cm/s and stoke rate was changed from 40 to 80 beats per minute (bpm). The results showed mean aggregated size (MAS) was increased as velocity amplitude variation was changed from 0.5 to 1.5cm/s. The maximum MAS happened when the aggregated number decreased. Another finding was that the time to reach the maximum of RBC MAS is shorter as stroke rate was increased from 40 to 80 bpm. In addition, MAS variation was related with mean velocity, and hematocrit. The simulated results are in good agreement with previous experimental results, showing ‘the Bright Collapsing Ring’ phenomenon and supporting the combined effects of flow acceleration and shear rate on RBC aggregation under pulsatile Poiseuille flow. [ABSTRACT FROM PUBLISHER]

In this paper the influence of body acceleration on the flow of blood through a stenosed catheterized artery is studied. The effect of non-Newtonian nature of blood in small blood vessels has been taken into account by modeling blood as Casson fluid. The governing equations of the fluid flow are solved using the perturbation technique, assuming the Wormsely number as small. The effect of catheterization, height of the stenosis, body acceleration on the flow shear stress and resistance to flow are studied. [ABSTRACT FROM AUTHOR]

A theoretical study of pulsatile blood flow through a constricted porous channel in the presence of an external magnetic field by considering the incompressible Newtonian fluid model is investigated. The influence of magnetic field on the flow is studied using the dimensionless magnetic parameter M and a Darcian linear impedance for low Reynolds number is taken into account in the transformed momentum equation. A perturbation method is employed to solve the governing differential equations by using a small perturbation parameter ? (such that 0 < ϵ << 1), which is incorporated in the time dependent transpiration velocity (suction/ injection). Using appropriate boundary conditions analytical expressions for the velocity distribution, volumetric flow rate and wall shear stress have been derived and the numerical results are presented graphically for different values of the physical parameters of interest. [ABSTRACT FROM AUTHOR]

The presented paper shows the possibility of using holographic interferometry and hot-wire anemometry in the research of heat transfer from impingement pulsatile flow. The intensity of heat transfer in the case of impingement flow is often measured with glue-on heat flux sensors, or by indirect methods such as naphthalene sublimation. All these methods have a response time too long for measuring instant values of the heat transfer coefficient on a surface cooled/heated by impingement pulsatile flow. This shortcoming should be overcome by using CTA glue-on probes or, preferably, by using optical methods such as holographic interferometry. It is necessary to employ a special holographic setup with double sensitivity instead of the commonly used Mach-Zehnder type of holographic interferometer in order to attain the parameters sufficient for the studied case. This setup is not light efficient like the Mach-Zehnder type but has double sensitivity. The results from the holographic interferometry experiments will be compared with the temperature field achieved by methods of hot-wire anemometry. [ABSTRACT FROM AUTHOR]