Pulsatile Blood Flows Through a Bileaflet Mechanical Heart Valve with Different Approach Methods of Numerical Analysis : Pulsatile Flows with Fixed Leaflets and Interacted with Moving Leaflets

Park, Choeng-Ryul,Kim, Chang-Nyung,Kwon, Young-Joo,Lee, Jae-Won The Korean Society of Mechanical Engineers 2003 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.17 No.7

Many researchers have investigated the blood flow characteristics through bileaflet mechanical heart valves using computational fluid dynamics (CFD) models. Their numerical approach methods can be classified into three types; steady flow analysis, pulsatile flow analysis with fixed leaflets, and pulsatile flow analysis with moving leaflets. The first and second methods have been generally employed for two-dimensional and three-dimensional calculations. The pulsatile flow analysis interacted with moving leaflets has been recently introduced and tried only in two-dimensional analysis because this approach method has difficulty in considering simultaneously two physics of blood flow and leaflet behavior interacted with blood flow. In this publication, numerical calculation for pulsatile flow with moving leaflets using a fluid-structure interaction method has been performed in a three-dimensional geometry. Also, pulsatile flow with fixed leaflets has been analyzed for comparison with the case with moving leaflets. The calculated results using the fluid-structure interaction model have shown good agreements with results visualized by previous experiments. In peak systole. calculations with the two approach methods have predicted similar flow fields. However, the model with fixed leaflets has not been able to predict the flow fields during opening and closing phases. Therefore, the model with moving leaflets is rigorously required for advanced analysis of flow fields.

Three-Dimensional Flow Visualization for the Steady and Pulsatile Flows in a Branching Model using the High-Resolution PIV System

Suh, Sang-Ho,Roh, Hyung-Woon Biomedical Engineering Society for Circulation 2004 International Journal of Vascular Biomedical Engin Vol.2 No.2

The objective of the present study is to visualize the steady and pulsatile flow fields in a branching model by using a high-resolution PIV system. A bifurcated flow system was built for the experiments in the steady and pulsatile flows. Harvard pulsatile pump was used to generate the pulsatile velocity waveforms. Conifer powder as the tracing particles was added to water to visualize the flow fields. CCD cameras($1K{\times}1K$(high resolution camera) and $640{\times}480$(low resolution camera)) captured two consecutive particle images at once for the image processing of several cross sections on the flow system. The range validation method and the area interpolation method were used to obtain the final velocity vectors with high accuracy. The results of the image processing clearly showed the recirculation zones and the formation of the paired secondary flows from the distal to the apex of the branch flow in the bifurcated model. The results also indicated that the particle velocities at the inner wall moved faster than the velocities at the outer wall due to the inertial force effects and the helical motions generated in the branch flows as the flow proceeded toward the outer wall. Even though the PIV images from the high resolution camera were closer to the simulation results than the images from the low resolution camera at some locations, both results of the PIV experiments from the two cameras generally agreed quite well with the results from the computer simulations. Therefore, instead of using the expensive stereoscopic PIV or 3D PIV system, the three-dimensional flow fields in a bifurcated model could be easily and exactly investigated by this study.

Simultaneous pulsatile flow and oscillating wall of a non-Newtonian liquid

E.E. Herrera-Valencia,M.L. Sánchez-Villavicencio,F. Calderas,M. Pérez-Camacho,L. Medina-Torres 한국유변학회 2016 Korea-Australia rheology journal Vol.28 No.4

In this work, analytical predictions of the rectilinear flow of a non-Newtonian liquid are given. The fluid is subjected to a combined flow: A pulsatile time-dependent pressure gradient and a random longitudinal vibration at the wall acting simultaneously. The fluctuating component of the combined pressure gradient and oscillating flow is assumed to be of small amplitude and can be adequately represented by a weakly stochastic process, for which a quasi-static perturbation solution scheme is suggested, in terms of a small parameter. This flow is analyzed with the Tanner constitutive equation model with the viscosity function represented by the Ellis model. According to the coupled Tanner-Ellis model, the flow enhancement can be separated in two contributions (pulsatile and oscillating mechanisms) and the power requirement is always positive and can be interpreted as the sum of a pulsatile, oscillating, and the coupled systems respectively. Both expressions depend on the amplitude of the oscillations, the perturbation parameter, the exponent of the Ellis model (associated to the shear thinning or thickening mechanisms), and the Reynolds and Deborah numbers. At small wall stress values, the flow enhancement is dominated by the axial wall oscillations whereas at high wall stress values, the system is governed by the pulsating noise perturbation. The flow transition is obtained for a critical shear stress which is a function of the Reynolds number, dimensionless frequency and the ratio of the two amplitudes associated with the pulsating and oscillating perturbations. In addition, the flow enhancement is compared with analytical and numerical predictions of the Reiner-Phillipoff and Carreau models. Finally, the flow enhancement and power requirement are predicted using biological rheometric data of blood with low cholesterol content.

FDM analysis for MHD flow of a non-Newtonian fluid for blood flow in stenosed arteries

D. S. Sankar,이우식 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.10

A computational model is developed to analyze the effects of magnetic field in a pulsatile flow of blood through narrow arteries with mild stenosis, treating blood as Casson fluid model. Finite difference method is employed to solve the simplified nonlinear partial differential equation and an explicit finite difference scheme is obtained for velocity and subsequently the finite difference formula for the flow rate, skin friction and longitudinal impedance are also derived. The effects of various parameters associated with this flow problem such as stenosis height, yield stress, magnetic field and amplitude of the pressure gradient on the physiologically important flow quantities namely velocity distribution, flow rate, skin friction and longitudinal impedance to flow are analyzed by plotting the graphs for the variation of these flow quantities for different values of the aforesaid parameters. It is found that the velocity and flow rate decrease with the increase of the Hartmann number and the reverse behavior is noticed for the wall shear stress and longitudinal impedance of the flow. It is noted that flow rate increases and skin friction decreases with the increase of the pressure gradient. It is also observed that the skin friction and longitudinal impedance increase with the increase of the amplitude parameter of the artery radius. It is also found that the skin friction and longitudinal impedance increases with the increase of the stenosis depth. It is recorded that the estimates of the increase in the skin friction and longitudinal impedance to flow increase considerably with the increase of the Hartmann number.

The Impact of Pulsatile Spiral Flow on the Wall Deformation Characteristics and Low-density Lipoproteins Accumulation in the Aorta

Ashraf, Fahmida,Cheema, Taqi Ahmad,Park, Cheol Woo Sciendo 2018 Applied rheology Vol.28 No.3

<P><B>Abstract</B></P><P>Spiral blood flow in the aorta is helpful in maintaining the stability of flow, reduction in lateral forces, turbulence near walls, and shear stress index. Thus, it helps in the prevention of diseases, such as atherosclerosis and atherogenesis, in the aortic arch because of the reduced accumulation of low-density lipoproteins (LDLs). To investigate the actual physics behind the aforementioned phenomenon, we conducted a fluid-structure interaction (FSI)-based numerical simulation of the three-dimensional aortic arch model under the influence of a pulsatile spiral flow. Spiral flow was introduced through the use of a mapping methodology between a spiral graft model and aortic model. The physics of time dependent pulsatile spiral turbulent flow was coupled with the structural mechanics of the aorta by using the FSI method. Results showed that the exterior interface of the aortic arch tends to rupture under the actions of centrifugal forces and secondary flow counter-rotating vortices in addition to applied pressure forces. Under systolic and diastolic conditions, the interior and exterior interfaces of the aortic arch both had small displacement, thus showing the insignificant role of velocity gradients in wall deformation. Moreover, LDL accumulation in the aorta under the influence of pulsatile spiral flow has been investigated using particle tracing methodology. The LDLs were evenly distributed in the aorta because of the influence of spiral flow. This result shows that spiral flow can contribute to the elimination of threats from diseases, such as atherosclerosis and atherogenesis.</P>

Sensorless measurement of the pulsatile flow through an implantable maglev centrifugal blood pump during ventricular assistance

Chi Nan Pai,Tadahiko Shinshi,Akira Shimokohbe 제어로봇시스템학회 2009 제어로봇시스템학회 국제학술대회 논문집 Vol.2009 No.8

We developed a centrifugal blood pump (CBP), incorporating a radial-controlled magnetic bearing (MB) and a brushless DC motor to assist the failing heart ventricle. To control the flow through the CBP, real-time measurement of pulsatile flow is required. However, the use of conventional flow sensors is not desirable due to issues of compactness and durability. The radial thrust acting on a magnetically levitated impeller depends on the pump flow. In this study, we present a method for estimating pulsatile flow during ventricular assistance, based on the radial thrust estimated by a disturbance force observer of the MB. To design this observer, parameters of the dynamic model of a magnetically levitated impeller were identified underdifferent flow conditions, assuming the density and viscosity of water to be constant. The disturbance force observers were designed based on linear models that were obtained for a given rotational speed. The relationship between pumpflow and radial thrust was first identified experimentally under non-pulsatile flow conditions. Then, using this relationship and the measured radial thrust, the pump flow was estimated under pulsatile flow conditions and a high correlation was achieved between the measured and the estimated flows.

Effect of body acceleration on pulsatile flow of Casson fluid through a mild stenosed artery

Nagarani, P.,Sarojamma, G. The Korean Society of Rheology 2008 Korea-Australia rheology journal Vol.20 No.4

The pulsatile flow of blood through a stenosed artery under the influence of external periodic body acceleration is studied. The effect of non-Newtonian nature of blood in small blood vessels has been taken into account by modeling blood as a Casson fluid. The non-linear coupled equations governing the flow are solved using perturbation analysis assuming that the Womersley frequency parameter is small which is valid for physiological situations in small blood vessels. The effect of pulsatility, stenosis, body acceleration, yield stress of the fluid and pressure gradient on the yield plane locations, velocity distribution, flow rate, shear stress and frictional resistance are investigated. It is noticed that the effect of yield stress and stenosis is to reduce flow rate and increase flow resistance. The impact of body acceleration is to enhance the flow rate and reduces resistance to flow.

Effect of body acceleration on pulsatile flow of Casson fluid through a mild stenosed artery

P. Nagarani,G. Sarojamma 한국유변학회 2008 Korea-Australia rheology journal Vol.20 No.4

The pulsatile flow of blood through a stenosed artery under the influence of external periodic body acceleration is studied. The effect of non-Newtonian nature of blood in small blood vessels has been taken into account by modeling blood as a Casson fluid. The non-linear coupled equations governing the flow are solved using perturbation analysis assuming that the Womersley frequency parameter is small which is valid for physiological situations in small blood vessels. The effect of pulsatility, stenosis, body acceleration, yield stress of the fluid and pressure gradient on the yield plane locations, velocity distribution, flow rate, shear stress and frictional resistance are investigated. It is noticed that the effect of yield stress and stenosis is to reduce flow rate and increase flow resistance. The impact of body acceleration is to enhance the flow rate and reduces resistance to flow.

Preliminary Study of a New Extracorporeal Membrane Oxygenator Development When Using Pulsatile Flow

Lee, Sa-Ram,Lee, Kyung-Soo,Jung, Jae-Hoon,Mun, Cho-Hay,Min, Byoug-Goo The Korean Society of Medical and Biological Engin 2007 의공학회지 Vol.28 No.3

An oxygenator is a very important artificial organ and widely used for patients with lung failure or during open heart surgery. Although an oxygenator has been widely studied worldwide to enhance its efficiency, studies on oxygenators, in particular when using a pulsatile blood flow, are domestically limited. Therefore, a new oxygenator was developed in the lab and animal experimental results are described in the paper. The oxygenator is composed of polycarbonate housing and polypropylene hollow fibers. It has a total length of 400 mm and a surface area of $1.7 m^2$. The animal experiment lasted for 4 hours. The blood flow rate was set to 2 L/min and a pulsatile blood pump, T-PLS (Twin-Pulse Life Support), was used. Samples were drawn at the oxygenator's inlet and outlet. The total hemoglobin (Hb), saturation oxygen ($sO_2$), and partial oxygen pressure ($pO_2$), partial $CO_2$ pressure ($pCO_2$), and plasma bicarbonate ion concentration ($HCO_3^-$) were measured. The oxygen and carbon dioxide transfer rates were also calculated based on the experimental data in order to estimate the oxygenator's gas transfer efficiency. The oxygen and carbon dioxide transfer rates were $16.4{\pm}1.58$ and $165.7{\pm}10.96 mL/min$, respectively. The results showed a higher carbon dioxide transfer rate was achieved with the oxygenator. Also, the mean inlet and outlet blood pressures were 162.79 and 137.92 mmHg, respectively. The oxygenator has a low pressure drop between its inlet and outlet. The aim of own preliminary study was to make a new oxygenator and review its performance when applying a pulsatile blood pump thus, confirming the possibility of a new oxygenator suitable for pulsatile flow.

Effects of surface geometry and non-newtonian viscosity on the flow field in arterial stenoses

정우원,이계한 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.9

Hemodynamics including flow pattern, shear stress, and blood viscosity characteristics has been believed to affect the development and progression of arterial stenosis, but previous studies lack of realistic physiological considerations such as irregular surface geometry, non-Newtonian viscosity characteristics and flow pulsatility. The effects of surface irregularities and non-Newtonian viscosity on flow fields were explored in this study using the arterial stenosis models with 48% arterial occlusions under physiological flow condition. Computational flow dynamics based on the finite volume method was employed for Newtonian and non-Newtonian fluid. The wall shear stresses (WSS) in the irregular surface model were higher compared to those in the smooth surface models. Also, non-Newtonian viscosity characteristics increase the peak WSS significantly. The dimensionless pressure drop and the time averaged WSS in pulsatile flow were higher than those in steady flow. But pulsatility effects on pressure and WSS were less significant compared to non-Newtonian viscosity effects. Therefore, irregular surface geometry and non-Newtonian viscosity characteristics should be considered in predicting pressure drop and WSS in stenotic arteries.