Fluid-Structure Interaction in Biological Media / FSI
Alireza Hashemifard; Nasser Fatouraee; Malikeh Nabaei
Volume 17, Issue 3 , December 2023, , Pages 201-210
Abstract
The crucial responsibility of the aortic valve is to prevent returning of blood flow from the aorta back to the left ventricle. In-time and accurate opening and closing of the aortic valve can effectively produce the desired blood pressure and cardiac output. For this reason, aortic valve simulation ...
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The crucial responsibility of the aortic valve is to prevent returning of blood flow from the aorta back to the left ventricle. In-time and accurate opening and closing of the aortic valve can effectively produce the desired blood pressure and cardiac output. For this reason, aortic valve simulation can identify changes related to aortic valve hemodynamics and their relationship. Diagrams of the left ventricular pressure, the left ventricular pressure difference relative to the aortic artery, GOA, blood flow, the left ventricle pressure-to-volume, the left ventricular energy, kinematic energy density, viscous dissipation, valve resistance, fluid pressure difference in two The surface side of the leaflets, and the momentary pressure difference of the longitudinal axis of the aortic valve compared to the pressure of the aortic artery are reported in this research and based on these, the process of opening and closing of the aortic valve is analyzed using numerical methods named ALE. The moving of the aortic leaflet as the displacement of the solid boundary in the fluid-solid interaction method causes the fluid mesh to undergo displacement and change, which is repaired by the sequence of re-meshing in the fluid domain. In this process, problems occur, the details of which and the resolving method are explained in detail.
Fluid-Structure Interaction in Biological Media / FSI
shahrokh shojaei; Shahrokh Shojaei
Volume 16, Issue 4 , March 2023, , Pages 41-50
Abstract
The pathological effects of the tumor on the respiratory airway have always been the focus of researchers. So, these effects will lead to the suffocation of the patient in acute cases. This study presents a computational model to investigate the effect of a tumor on the airflow in the larynx area with ...
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The pathological effects of the tumor on the respiratory airway have always been the focus of researchers. So, these effects will lead to the suffocation of the patient in acute cases. This study presents a computational model to investigate the effect of a tumor on the airflow in the larynx area with the help of Ansys software. The presented model is able to numerically calculate the effect of tumor presence on airspeed and pressure in the upper air system. This study considered the simulation of steady airflow for exhalation in three respiratory flow rates of 15 L/min, 26 L/min, and 30 L/min. The maximum speed limit in the respiratory flow of L/min 15, L/min 26, and L/min 30, respectively, 6.26 m/s, 10.58 m/s, and 12.14 m/s, appears in the larynx. Also, the highest pressure occurs in the trachea, so the maximum pressure in the respiratory rate is 15 L/min, 26 L/min, and 30 L/min, respectively, equal 19.6 Pa, 51.01 Pa, and 65.8 Pa. On the other hand, most deformation occurs in the area of narrowing of the respiratory tract. With the increase in the flow rate, the amount of deformation also increases. The maximum deformation on the wall at the respiratory flow rate of 15 L/min, 26 L/min, and 30 L/min is equal to 0.07mm, 0.2mm, and 0.27mm, respectively. Due to the presence of a tumor in this respiratory model, velocity and WSS reach their maximum in the larynx region. The presence of a tumor can gradually lead to airway obstruction. Moreover, the risk of airway obstruction increases even in a slight reduction in respiratory capacity. Providing a numerical model for the respiratory system can effectively lead to a better treatment approach.
Biofluid Mechanics / Biofluids
Mohammad Ahmadi Alashti; Bahman Vahidi; Mahtab Ebad
Volume 13, Issue 1 , April 2019, , Pages 1-15
Abstract
The large surface area of the lung with its thin air-blood barrier is exposed to particles in the inhaled air. In this condition, if the inhaled pollutant aerosols are toxic, the particle-lung interaction may cause serious hazards and injuries on human’s health. On the otherhand, these interactions ...
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The large surface area of the lung with its thin air-blood barrier is exposed to particles in the inhaled air. In this condition, if the inhaled pollutant aerosols are toxic, the particle-lung interaction may cause serious hazards and injuries on human’s health. On the otherhand, these interactions are also used for drug delivery to human’s body. In either case, an accurate estimation of dose and sites of deposition in the respiratory tract is fundamental for understanding mechanobiology of these deseases. Obtaining in vivo data of particle transportation in the human lung experimentally is often difficult. But, computational fluid-particle dynamics (CFPD) has provided the possibility to gain aerosol transportion data in realistic airway geometries. Aerosols deposition in the human lung mainly occurs due to combination of inertial impaction, gravitational sedimentation and diffusion. For particles with aerodynamic size of 0.5 to 5 micron and in inhalation state of lung, the main mechanisms of particle deposition in distal parts of human’s respiratory system are sedimentation, due to gravity and convective transfer due to wall movement. In this study, deposition of particles in distal part of human respiratory system, specifically 18th generation, has been modeled for two gravity conditions, normal and absent gravity, by assuming isotropic displacements on the walls and with the rate of 1 (mg/sec) for particle input. By analyzing the results, it was determined that the amount of particle deposition in distal airways reduces a great amount by omitting the effect of gravitational force because, particles smaller than 5 micron can penetrate into that airways. Particles with the diameter of 5 micron deposit under the effect of inertial impact, whereas this mechanism occurs mostly in airways with large and medium diameters and also, by sedimentation which occurs in the distal lung.
Fluid-Structure Interaction in Biological Media / FSI
Ali Vazifedoost Saleh; Nasser Fatouraee; Mahdi Navidbakhsh; Farzad Izadi
Volume 11, Issue 2 , June 2017, , Pages 153-165
Abstract
In terms of mechanical behavior, human’s speaking and generating voice is a sophisticated process which is resulted in interaction between flowing air through the larynx and oscillating functionality of vocal folds. The sulcus vocalis is one of the individual cases of scarring in which the superficial ...
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In terms of mechanical behavior, human’s speaking and generating voice is a sophisticated process which is resulted in interaction between flowing air through the larynx and oscillating functionality of vocal folds. The sulcus vocalis is one of the individual cases of scarring in which the superficial lamina propria is absent over the length of the vocal fold and can procreate several disorders in voice generation. In this study, for the first time, the effects of sulcus vocalis on vibrating functionality of vocal folds have been assessed by employing finite element numerical modeling. Two-dimensional models of either healthy or sulcus vocal folds were implemented which each one is coupled and solved via LS-dyne software. Also, the three e-layer linear elastic model was utilized for the structure phase and the arbitrary Lagrangian-Eulerian (ALE), incompressible continuity, and Navier- Stokes relations were used for the fluid domain. Type II patients’ self-excited oscillations have been exhibited and compared with the healthy model. The results of the healthy model were assessed and compared with numerical and experimental results of previous studies. Moreover, the influences of the sulcus not only on the flow components but also on the oscillating functionality of the vocal folds have been evaluated. The results indicated that the frequency of vocal folds’ vibrations and the value of volume flux tends to be remarkably declined and boosted up respectively.
Fluid-Structure Interaction in Biological Media / FSI
Hoda Mastari Farahani; Nasser Fatouraee
Volume 10, Issue 3 , October 2016, , Pages 223-230
Abstract
Syrinx growth in Syringomyelia desease causes progressive neurological disorders. Thus, the examination of effective factors in syrinx development is so important for controlling this desease. One of clinical assumptions related to the reason of syrinx development, considers the propagation of pressure ...
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Syrinx growth in Syringomyelia desease causes progressive neurological disorders. Thus, the examination of effective factors in syrinx development is so important for controlling this desease. One of clinical assumptions related to the reason of syrinx development, considers the propagation of pressure wave shock in subarachnoid-space fluid as the main reason for fluid motion in syrinx and syrinx development and increasing damage to spinal cord. Modeling and analysis have been performed to test the theory in this research using finite element method. So a 3d model was created including syrinx, spinal cord, cerebrospinal-fluid in subarachnoid-space, dura mater and stenosis. Pressure puls stimulation was applied to the superior surface of the subarachnoid-space fluid model simulating arterial puls of skull. Cerebrospinal-fluid has been assumed as a Newtonian fluid with laminar flow. The solid phase has been considered to be linear elastic. The fluid-solid interface was analized using ADINA software and fluid flow characteristics were extracted including velocity and pressure field as well as tissue stresses. Results show that pressure wave propagation in subarachnoid-space fluid causes the induction of motion in syrinx fluid, and stress concentration is created in spinal tissue due to the fluid cessation in syrinx and increasing local pressure, however these stress values are lower than spinal tissue strength and pressure wave propagation in this situation cannot be the main reason of syrinx development.
Fluid-Structure Interaction in Biological Media / FSI
Saeed Bahrami; Mahmood Norouzi
Volume 10, Issue 2 , August 2016, , Pages 175-186
Abstract
Increasing the cardiovascular disease had led to the researchers to investigate the blood flow more than before. In this article the effects of artery elasticity on hemodynamic parameters with concerning the interaction between blood and the vessel’s wall had been investigated. The wall shear stress ...
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Increasing the cardiovascular disease had led to the researchers to investigate the blood flow more than before. In this article the effects of artery elasticity on hemodynamic parameters with concerning the interaction between blood and the vessel’s wall had been investigated. The wall shear stress had changed with different times and cannot send the congestion of the vessels. From this point the oscillatory shear index had been said the shear stress without the time average. In this study a 3D model from the left coronary bifurcation with 4 models of wall had been investigated. The result from a pulsatile flow from a non-newtonian flow with the method of two ways coupling by using the method of arbitrary Lagrangian–Eulerian had been calculated. The observation had showed a 13 percent decreasing in the profile of velocities at the bifurcation place in that in the hyperelastic model had the highest subtraction. Also by increasing the toughness of the wall the velocity profile and oscillator shear stress were increased. The average shear stress in the model of rigid had showed the 28 percent difference in comparison with the hyperelastic model. By comparing the results with clinical data showed that, the places with average shear stress 1.10 pa and less than that with presenting the oscillatory shear index is more than 0.3 that can be a potential dangerous places in forming atherosclerosis oscillatory shear index plaque especially in the posterior after the bifurcation. Meanwhile in the hyperelastic model the results are more precise than the other models.
Fluid-Structure Interaction in Biological Media / FSI
Saeid Siri; Malikeh Nabaei; Nasser Fatouraee
Volume 9, Issue 3 , December 2015, , Pages 229-241
Abstract
Every organ has its own metabolic and functional requirements and needs a variable amount of blood; hence, autoregulation is an important phenomenon. Shear stress induced autoregulation is defined as the innate ability of an organ to keep its hemodynamic conditions stable against changes in heart rate ...
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Every organ has its own metabolic and functional requirements and needs a variable amount of blood; hence, autoregulation is an important phenomenon. Shear stress induced autoregulation is defined as the innate ability of an organ to keep its hemodynamic conditions stable against changes in heart rate and perfusion pressure. For example, when heart rate changes arterial vessels undergo vasodilation or vasoconstriction in order to stabilize the hemodynamic forces and stresses with respect to the flow needed. The current study examines the local mechanisms employed in automatic control. Local regulatory mechanisms function independently of external control mechanisms, such as sympathetic nerves and endocrine hormones. Therefore, they can be considered isolated mechanisms. The application of boundary conditions in numerical modeling is of utmost importance, hence, using arterial tree modeling to achieve appropriate boundary conditions seems necessary. Thus, we have presented a zero-dimensional (lumped parameter) extensive model first. Then, we used this model to achieve boundary conditions for the common carotid artery. As one of the most important hemodynamic parameters, shear stress regulation will then be modeled in an axisymmetric model of this artery.
Fluid-Structure Interaction in Biological Media / FSI
Mahdi Moradkhani; Bahman Vahidi
Volume 9, Issue 2 , July 2015, , Pages 179-190
Abstract
Investigating the mechanical stimuli on stem cells under in vitro and in vivo conditions is a very important topic to achieve an ability tocontrol the cellular responses like growth, proliferation and differentiation. Many investigations carried out about biomechanical factors involved in this phenomenon ...
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Investigating the mechanical stimuli on stem cells under in vitro and in vivo conditions is a very important topic to achieve an ability tocontrol the cellular responses like growth, proliferation and differentiation. Many investigations carried out about biomechanical factors involved in this phenomenon and nowadays, it is proved that some factors like as cell morphology, subcellular elements configuration, scaffold architecture, substrate stiffness and mechanical stimulation via substrate displacement or fluid flow, have got an important effecton cellular responses. In this study, we have tried to evaluate the responses of a stem cell to the stiffness and thickness of the substrate by the means of finite element method. For this purpose, we have used collagen-based scaffolds as the artificial ECM and a cell culture in a bioreactor with fluid flow was simulated. By use of fluid-structure interaction method and solving the equations in two-way coupling scheme, the results show that the increase in thickness and stiffness of the substrate will result in15 percent change in cell-substrate stresses, respectively. Also, it was seen that the change of substrate stiffness only in the range of 0.1-100 KPa could affect the cell response to an external stimulation. These results, along with other similar investigations, could be used as an instructor by the researchers to optimize the stem cell’s microenvironment in vitro, and finally get the most out of their stem cell related Investigations.
Fluid-Structure Interaction in Biological Media / FSI
Saeed Nahidi; Alireza Hossein-Nezhad; Nasser Fatouraee; Zahra Heidari
Volume 7, Issue 2 , June 2013, , Pages 107-120
Abstract
Blood flow parameters are affected by position and shape of the accumulation of low density lipoprotein (LDL) in the layers of the arterial wall, and this phenomenon itself is influenced by infiltration flow of the blood. In this paper, in order to investigate the effect of wall flexibility on the infiltration ...
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Blood flow parameters are affected by position and shape of the accumulation of low density lipoprotein (LDL) in the layers of the arterial wall, and this phenomenon itself is influenced by infiltration flow of the blood. In this paper, in order to investigate the effect of wall flexibility on the infiltration flow in a pulsatile non-Newtonian blood flow in a symmetric carotid artery stenosis with a two flexible and porous layers, a finite element model with Porous Fluid Structure Interaction (PFSI) method was used and the results were compared to the porous rigid model. Study parameters were investigated in three different stenosis severities. Comparison of the presented results using PFSI model with those of Porous Rigid model showed about 22% decrease in wall shear stress in the stenosis region, about 20% increase in filtration velocity in the pre- and post-stenosis regions of the porous layer, but a slight difference in filtration velocity in the stenosis region.
Biomimetics
Behzad Seyfi; Hosein Mansourinejad; Bahman Vahidi; Nasser Fatouraee
Volume 6, Issue 3 , June 2012, , Pages 169-175
Abstract
Peristaltic flow is one of the important mechanisms of fluid transmission. In addition to the divers engineering applications, this mechanism plays an important role in biological organs such as digestion system and urine excretion. In this paper, urine bolus transportation in ureter has been investigated ...
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Peristaltic flow is one of the important mechanisms of fluid transmission. In addition to the divers engineering applications, this mechanism plays an important role in biological organs such as digestion system and urine excretion. In this paper, urine bolus transportation in ureter has been investigated experimentally using a peristaltic flow simulator apparatus. Some of the features of this apparatus worth mentioning are its ability to use it to investigate the influence of some important parameters in peristaltic flow, such as the effect of pressure difference between the kidney and the bladder on the quantity of discharge and reflux rates, effect of the mean velocity of bolus transport on discharge rate, existence of fluid film and its effect on bolus discharge rate, and effect of fluid bolus length on reflux rate. Then we compare the obtained results with the similar theoretical studies. It was observed that an increase in the pressure difference between inlet and outlet decreases the ratio of reflux to initial volume of the bolus, and it increases the discharge rate. Moreover, the quantities of reflux and discharge rate decrease by decreasing the bolus transport velocity. It was also observed that the thickness of the fluid film has an inverse relation with respect to the discharge rate and with increasing the bolus length reflux is increasing.
Fluid-Structure Interaction in Biological Media / FSI
Saeed Nahidi; Alireza Hossein-Nezhad; Nasser Fatouraee; Zahra Heidari
Volume 6, Issue 1 , June 2012, , Pages 71-79
Abstract
Hemodynamic parameters are always affected by stenosis severity of arterial and these parameters in their turn have influence on the development of atherosclerosis. In this paper, By considering three different stenosis severity, the effects of wall porosity assumption on the hemodynamic parameters of ...
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Hemodynamic parameters are always affected by stenosis severity of arterial and these parameters in their turn have influence on the development of atherosclerosis. In this paper, By considering three different stenosis severity, the effects of wall porosity assumption on the hemodynamic parameters of a stenosed artery with a two-layer flexible wall (intima-media, adventitia), in which inner layer (intima-media) assumed porous, is numerically investigated, using Porous Fluid Structure Interaction (PFSI) model. Blood is assumed as an incompressible non-Newtonian fluid with pulsatile flow condition. In this investigation, the results show that the permeability assumption has much influenced on the hemodynamic characteristics so that the comparison of the results using PFSI with those of a non-porous model show 6% decrease in shear stress, 30% increase in displacement and more than 72% increase in effective stress in the porous layer.
Fluid-Structure Interaction in Biological Media / FSI
Alireza Hashemi Fard; Nasser Fatouraee
Volume 5, Issue 1 , June 2011, , Pages 1-12
Abstract
The heart muscle is supplied via the coronary arteries. The coronary arteries are deformed in each cardiac cycle by the contraction of the myocardium. The aim of this work was to investigate the effects of physiologically idealized cardiac-induced motion on flow rate in human left coronary arteries. ...
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The heart muscle is supplied via the coronary arteries. The coronary arteries are deformed in each cardiac cycle by the contraction of the myocardium. The aim of this work was to investigate the effects of physiologically idealized cardiac-induced motion on flow rate in human left coronary arteries. The blood flow rate were numerically simulated in an elastic modeled left anterior descending coronary artery (LAD) having a uniform circular cross section. Blood was considered to be a non-Newtonian fluid and Arterial motion was specified based on monoplane physiologically idealized bending. Simulations were carried out with dynamic pressure difference conditions between inlet and outlet in both fixed and moving LAD models, to evaluate the relative importance of LAD motion, flow rate, and the interaction between motion and time-averaged flow rate. LAD motion was caused variations in time-averaged flow rate in the moving LAD models as compare as the fixed models. There was significant variability in the magnitude of this motion-induced flow variation. However, the magnification of time-averaged flow rate is depending to specification of the cardiac motion. Furthermore, the effects of pressure pulsatility dominated LAD motion induced effects; specifically, there were local flow variation and secondary flow in the simulations conducted in moving LAD models.
Fluid-Structure Interaction in Biological Media / FSI
Borhan Alhoseini Hamedani; Mehdi Navidbakhsh; Hosein Ahmaditafti
Volume 5, Issue 1 , June 2011, , Pages 45-56
Abstract
In this paper, study of mechanical properties of human blood vessels is considered, especially those of related to the Coronary Artery Bypass Graft (CABG). Unfortunately more than 30% of saphenous grafts are re-occluded within 10 years while mammary artery shows better results. In this study elastomechanical ...
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In this paper, study of mechanical properties of human blood vessels is considered, especially those of related to the Coronary Artery Bypass Graft (CABG). Unfortunately more than 30% of saphenous grafts are re-occluded within 10 years while mammary artery shows better results. In this study elastomechanical properties of human saphenous vein, which is common in CABG, is studied. Stress-stretch behavior of these samples after a cyclic loading was obtained and large deformation formulation was used to obtain real stress and stretch ratio of these vessels. Then a fourth order polynomial was used to show nonlinear behavior of these results. Results show that blood vessel stiffness in longitudinal direction is two times greater than circumferential direction, while it is more than 74% stretchable in the circumferential direction. So modulus of elasticity in longitudinal direction is greater than circumferential direction. If we continue stretching until final rupture after maximum strength, longitudinal samples will be broken down faster than circumferential samples because of collagen fibers orientation.
Fluid-Structure Interaction in Biological Media / FSI
Hamed Khalesi; Hanie Niroomand Oscuii; Farzan Ghalichi
Volume 5, Issue 1 , June 2011, , Pages 67-78
Abstract
Biomechanics believe that, the arteries are remodeled under the influence of hemodynamic and mechanical factors. Biomechanical factors such as Opening Angle and the Tethering could have important effects on this phenomenon. The effects of various Opening Angle and Tethering during thoracic aorta aging ...
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Biomechanics believe that, the arteries are remodeled under the influence of hemodynamic and mechanical factors. Biomechanical factors such as Opening Angle and the Tethering could have important effects on this phenomenon. The effects of various Opening Angle and Tethering during thoracic aorta aging on arterial wall stress have been studied. ADINA software is used for numerical simulation.In this study, for the first time, numerical methods of Fluid-Structure Interaction have been used to study and simulate effects of Opening Angle and the Tethering in elastic artery remodeling due to age. Large deformation theory has been used for modeling changes of arterial radius; furthermore, behavior of Newtonian fluid has been used for blood. Pulsatile pressure and physiological Pulsatile flow waveforms have been applied to simulate transient behavior of arterial system. The results show that opening angle has further effect on circumferential stress so smooth distribution of circumferential stress on the wall accrued. Also, increasing Opening Angle with age reverses the circumferential stress distribution slop across the arterial wall. Tethering has further effect on axial stress. Decreasing Tethering in remodeling process over age leads to increase stress levels in the aged artery. Also, arterial wall shear stress in remodeled artery shows significant reduction in maximum, mean and amplitude values that caused reduction of pathological effects of endothelial cells.
Fluid-Structure Interaction in Biological Media / FSI
Hanie Niroomand Oscuii; Farzan Ghalichi; Mohammad Tafazzoli Shadpour
Volume 2, Issue 1 , June 2008, , Pages 1-8
Abstract
In this paper, we studied the effect of mechanical loading on remodeling process with aging in muscular arteries. Based on the gathered experimental data, the brachial artery was selected for simulation. In this simulation, pulsatile pressure and flow waves were considered as boundary conditions to study ...
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In this paper, we studied the effect of mechanical loading on remodeling process with aging in muscular arteries. Based on the gathered experimental data, the brachial artery was selected for simulation. In this simulation, pulsatile pressure and flow waves were considered as boundary conditions to study the effect of circumferential stress and wall shear stress on the remodeling process. FSI based transient numerical simulation was used to solve the fluid and solid equations. The results of three remodeling schemes showed that inward eutrophic scheme is an optimum algorithm for brachia! Artery remodeling with aging. Such remodeling scheme causes the most optimized outcome to keep circumferential stress with minimal alteration.
Fluid-Structure Interaction in Biological Media / FSI
Afsane Mojra; Mohammad Tafazzoli Shadpour; Ehsan Yakhshi Tafti
Volume 2, Issue 1 , June 2008, , Pages 9-20
Abstract
Arterial stenosis and the consequent cardiovascular diseases such as atherosclerosis remain the major cause of mortality in the world. In this study, blood flow was analyzed in a three-dimensional model of stenosed carotid artery with asymmetric stenosis utilizing fluid-structure interaction method. ...
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Arterial stenosis and the consequent cardiovascular diseases such as atherosclerosis remain the major cause of mortality in the world. In this study, blood flow was analyzed in a three-dimensional model of stenosed carotid artery with asymmetric stenosis utilizing fluid-structure interaction method. The modeling was performed by ANSYS finite element software. To overcome the software inconsistency in FSI mode, a new code was designed in ANSYS multi-physics environment for coupling of solid and fluid domains via incremental boundary iteration method. The results indicated a considerable variation of local blood pressure, velocity and shear stress in stenosed artery, high pressure drop along stenosis, compressive stress and larger flow separation zone in the post-stenotic region as the result of increased eccentricity of stenosis. The results might be applied in evaluation of plaque severity, progression of disease, plaque growth and vulnerable regions of plaque to fracture.
Fluid-Structure Interaction in Biological Media / FSI
Bahman Vahidi; Nasser Fatouraee
Volume 2, Issue 4 , June 2008, , Pages 285-296
Abstract
Arterial embolism is one of the major killers of the people who have heart diseases. In cerebral arteries, the danger of embolism is that the ruptured particles are carried into the brain, provoking neurological symptoms or a stroke. In this research, for the first time, we have presented a numerical ...
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Arterial embolism is one of the major killers of the people who have heart diseases. In cerebral arteries, the danger of embolism is that the ruptured particles are carried into the brain, provoking neurological symptoms or a stroke. In this research, for the first time, we have presented a numerical model to study the complete blockage of the human common carotid artery resulted from the physical motion of a blood clot bulk with spherical geometry in it. In the numerical model, a transient flow was assumed in an axisymmetric finite length tube. The incompressible Navier-Stokes equations were used as the governing equations for the fluid and a linear elastic model was utilized for the blood clot bulk. In order to model the contact conditions between the blood clot and arterial wall, an axisymmetric rigid contact model was used. The arbitrary Lagrangian-Eulerian formulation (ALE) was applied to analyze the solid large displacements inside fluid flow. The results indicated that during contact between stenosis and the clot, separation and reattachment regions were occurred on the stenosis extensively which are susceptible to thrombosis onset and growth. By abruption of the clot from the arterial wall during its passage through the stenosis, an extensive recirculation zone occurred downstream of the stenosis and beneath the moving clot bulk. Analysis of the clot motion and deformation have showed that when the clot passed the stenosis completely, the areas near the clot peak had a large tendency to expand which indicated the propensity of these areas to disperse.
Fluid-Structure Interaction in Biological Media / FSI
Bahman Vahidi; Nasser Fatouraee; Ali Imanparast
Volume 2, Issue 1 , June 2008, , Pages 29-37
Abstract
Ureter reflux is one of the prevalent factors that causes pyelonefrit and sistit syndromes. Dilatation of ureter, renal pelves and calyx are detectable with reflux. In this paper, in order to analyze this phenomenon, an axisymmetric model was introduced. We utilized a rigid body, which is in contact ...
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Ureter reflux is one of the prevalent factors that causes pyelonefrit and sistit syndromes. Dilatation of ureter, renal pelves and calyx are detectable with reflux. In this paper, in order to analyze this phenomenon, an axisymmetric model was introduced. We utilized a rigid body, which is in contact with the outer ureter wall to model ureter contraction. The Navier-Stokes equations are solved for the fluid and a linear elastic model is used for ureter wall structure. The finite element equations for both the structure and the fluid were solved by the Newton-Raphson iterative method. The effect of ureter wall elasticity, pressure difference between the ureter inlet and outlet and the effect of the average velocity of peristaltic wave along the length of the ureter on the ureter outlet flow rate were analyzed. Moreover, the effect of the number of contraction waves on the pressure and flow relations in the ureter was analyzed. Increase in the number of contraction waves reduced the flow passing through the ureter. The results of investigating about the contraction wave velocity variations indicated that if average velocity the contraction wave was lower than a limited magnitude, its existence did not have any considerable effect on the ureter outlet flow rate. Finally improper function of urinary tubes junctions results in the passage of a part of back flow even in the case of low velocity beginning of the contraction wave.
Fluid-Structure Interaction in Biological Media / FSI
Hamed Avari; Farzan Ghalichi; Majid Ahmadlouy Darab
Volume 2, Issue 1 , June 2008, , Pages 39-46
Abstract
Adjusting the rhythm of breath is one of the important parameters that a successful athlete must consider. In this paper, the relationship between man's activity and respiration rhythm is studied. A numerical simulation is carried out on a 2D axi-symmetric model using computational fluid dynamics (CFD) ...
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Adjusting the rhythm of breath is one of the important parameters that a successful athlete must consider. In this paper, the relationship between man's activity and respiration rhythm is studied. A numerical simulation is carried out on a 2D axi-symmetric model using computational fluid dynamics (CFD) method. The model considers the oxygen uptake in the pulmonary capillaries in alveolar microcirculation system. The geometry consists of three main parts: a stationary capillary membrane, a moving plasma region and four semi-circular-shaped RBCs. Results show an inverse relationship between saturation time of RBCs and respiration rhythm. Using an inversion factor, a relationship is presented to assess the proper respiration rhythm for different exercise states.
Fluid-Structure Interaction in Biological Media / FSI
Farzan Ghalichi; Majid Ahmadlouy Darab; Ahmad Ramezani Saadatabadi
Volume 1, Issue 2 , June 2007, , Pages 111-117
Abstract
In order to compare the aorta-coronary and coronary-coronary bypasses blood flow fields in the Endto-Side Anastomosis, we carried out numerical simulation of three dimensional pulsatile blood flow for 50% stenosis by using FLUENT 5.2.3 software. In this study, the blood was assumed to be as the Newtonian, ...
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In order to compare the aorta-coronary and coronary-coronary bypasses blood flow fields in the Endto-Side Anastomosis, we carried out numerical simulation of three dimensional pulsatile blood flow for 50% stenosis by using FLUENT 5.2.3 software. In this study, the blood was assumed to be as the Newtonian, incompressible and homogeneous fluid. The arterial wall was also considered to be rigid. Non-existence of the secondary flows in the coronary-coronary bypass blood flow fields for various degrees of bypass grafting angles against the aorta-coronary-coronary bypass, return of total blood flow toward upstream in the coronary-coronary bypass three times over a heart cycle, high temporary oscillation in the wall shear stress magnitudes for the aorta-coronary bypass and low wall shear stress magnitudes for the coronary-coronary bypass were of the important results.
