Two-fluid non-Newtonian models for blood flow in catheterized arteries - A comparative study

D. S. Sankar,Usik Lee 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.9

Steady flow of blood through catheterized arteries is studied by assuming the blood as a two-fluid model with the suspension of all the erythrocytes in the core region as a non-Newtonian fluid and the plasma in the peripheral layer as a Newtonian fluid. The non-Newtonian fluid in the core region of the artery is modeled as (i) Casson fluid and (ii) Herschel-Bulkley fluid. The expressions for the shear stress, velocity, flow rate, wall shear stress and flow resistance, obtained by Sankar and Lee (2008a, 2008b) for the two-fluid Casson model and two-fluid Herschel-Bulkley model are used to get the data for comparison. It is noticed that the plug flow velocity, velocity distribution and flow rate for the two-fluid H-B model are considerably higher than that of the two-fluid Casson model for a given set of values of the parameters. Further, it is found that the resistance to flow is significantly lower for the two-fluid H-B model than that of the two-fluid Casson model. Thus, the two-fluid H-B model is more useful than the two-fluid Casson model to analyze the blood flow through catheterized arteries.

Observation of fluid layering and reverse motion in double-walled carbon nanotubes

K. Yaghmaei,H. Rafii-Tabar 한국물리학회 2009 Current Applied Physics Vol.9 No.6

Most modelling-based research in the field of carbon nanotube-related nano-fluidics has been concerned with the fluid flow in single-walled carbon nanotubes (SWCNTs), showing that the dynamics of the channel affect the structure and behaviour of the fluid. We have extended this work by modelling the flow of Ar in a double-walled carbon nanotube, and have modelled the flow in both the inner shell and the outer annular region of such a nanotube. We have found that the flows in these channels are strongly correlated, such that the fluid moves in opposite directions in these two regions. This phenomenon can give rise to a circulatory motion which can be exploited in nano-fluidic devices. Fluid layering phenomenon, that is usually associated with the flow of fluids in nano-scale channels, is also observed. Furthermore, we have also found that the fluid velocity in dynamic channels is smaller than in static channels, in line with the findings reported for single-walled carbon nanotubes. Most modelling-based research in the field of carbon nanotube-related nano-fluidics has been concerned with the fluid flow in single-walled carbon nanotubes (SWCNTs), showing that the dynamics of the channel affect the structure and behaviour of the fluid. We have extended this work by modelling the flow of Ar in a double-walled carbon nanotube, and have modelled the flow in both the inner shell and the outer annular region of such a nanotube. We have found that the flows in these channels are strongly correlated, such that the fluid moves in opposite directions in these two regions. This phenomenon can give rise to a circulatory motion which can be exploited in nano-fluidic devices. Fluid layering phenomenon, that is usually associated with the flow of fluids in nano-scale channels, is also observed. Furthermore, we have also found that the fluid velocity in dynamic channels is smaller than in static channels, in line with the findings reported for single-walled carbon nanotubes.

Inferred fluid flow through fault damage zones based on the observation of stalactites in carbonate caves

Kim, Y.S.,Sanderson, D.J. Pergamon Press 2010 Journal of structural geology Vol.32 No.9

Faults and fractures are important factors that control fluid flow in rock masses in hydrothermal, groundwater, and hydrocarbon systems. In this paper we examine local variations in fluid flow as evidenced by the distribution patterns and sizes of stalactites in fractured limestone. We observe that the size and distribution of stalactites relate to fluid flow and is strongly controlled by the fracture apertures, intersection of fractures, and development of damage zones around a fault. Fault damage zones are the volumes of deformed wall rocks around a fault surface that result from the initiation, propagation, interaction, termination, and build-up of slip along the fault. They are divided into tip-, wall-, and linkage damage zones depending on their location along the fault. The pattern of deformation within a damage zone mainly depends on fault tip modes (mode II or III), the 3-D locations around a fault surface, and the evolutionary stage of the fault. The development of different structures within damage zones gives valuable information about fault initiation and termination, fault propagation and growth, and fluid flow. Stalactites indicate fluid flow variation within a fault in that fluid flow is high in dilational jogs, variable along the main fault traces, and low in contractional jogs. Variation in ore fluid flow within faults is also important in controlling the position of ore shoots in structurally-controlled hydrothermal mineral deposits. Thus, the characteristics of fluid flow in fractured carbonate rocks can be related to patterns of damage around faults. Hence, the mapping of damage zones can be applied to the study of fracture-controlled fluid flow in the fields of petroleum geology, hydrogeology, and ore deposits.

Fluid Dynamic Efficiency of an Anatomically Correct Total Cavopulmonary Connection: Flow Visualizations and Computational Fluid Dynamic Studies

Yun, S.H.,Kim, S.Y.,Kim, Y.H. Biomedical Engineering Society for Circulation 2003 International Journal of Vascular Biomedical Engin Vol.1 No.2

Both flow visualizations and computational fluid dynamics were performed to determine hemodynamics in a total cavopulmonary connection (TCPC) model for surgically correcting congenital heart defects. From magnetic resonance images, an anatomically correct glass model was fabricated to visualize steady flow. The total flow rates were 4, 6 and 8L/min and flow rates from SVC and IVC were 40:60. The flow split ratio between LPA and RPA was varied by 70:30, 60:40 and 50:50. A pressure-based finite-volume software was used to solve steady flow dynamics in TCPC models. Results showed that superior vena cava(SVC) and inferior vena cava(IVC) flow merged directly to the intra-atrial conduit, creating two large vortices. Significant swirl motions were observed in the intra-atrial conduit and pulmonary arteries. Flow collision or swirling flow resulted in energy loss in TCPC models. In addition, a large intra-atrial channel or a sharp bend in TCPC geometries could influence on energy losses. Energy conservation was efficient when flow rates in pulmonary branches were balanced. In order to increase energy efficiency in Fontan operations, it is necessary to remove a flow collision in the intra-atrial channel and a sharp bend in the pulmonary bifurcation.

Tidally-influenced deposition and microfacies sequences of fluid muds: Early Cretaceous McMurray Formation, Alberta, Canada

오주현,조형래 한국지질과학협의회 2021 Geosciences Journal Vol.25 No.6

Fluid muds are common in estuarine environments, but their ancient examples have rarely been documented due to poor comprehension of their depositional processes and characteristics. Mudstone layers in the tidally-influenced channel sequences of the middle McMurray Formation are examined in detail through microscopic observations and interpreted on the basis of recent advances in the understanding of flow dynamics of high mud-concentration flows. The mudstone layers, < 1 to 25 mm thick, are classified into three microfacies. Structureless mudstone (Microfacies 1) consists mainly of clay particles with randomly dispersed coarse grains (coarse silt to fine sand). It represents cohesive mud flows with sufficient cohesive forces to support coarse grains (quasi-laminar plug flow). Siltstreaked mudstone (Microfacies 2) is similar to Microfacies 1 in texture, but contains discontinuous streaks of coarse-silt to very-finesand grains. It is interpreted as being also deposited by cohesive fluid muds. The silt streaks are, however, suggestive of the presence of weak turbulence under the cohesive plug (upper transitional plug flow). Heterolithic laminated mudstone (Microfacies 3) is characterized by alternations of very thin, silt and clay laminae, which are either parallel or low-angle cross-laminated. It is interpreted as the deposits of low-amplitude bed-waves formed in lower transitional plug flows. These microfacies reflect a range of flow phases of fluid muds, which changed as flow velocities and suspended sediment concentrations fluctuated with tidal cycles. Repeated vertical changes of microfacies are suggestive of an ideal sequence of fluid muds formed during tidal acceleration and deceleration. The sequence comprising microfacies 3, 2 and 1 in ascending order represents deposition from lower transitional plug flows through upper transitional plug flows to quasi-laminar plug flows as suspended sediment concentrations increase with flow deceleration. That of the reversed order of microfacies reflects the reversed change in flow types during acceleration. These results provide the basis for recognizing fluid-mud deposits and tidal signatures in ancient estuarine sequences.

A two-layered suspension (particle-fluid) model for non-Newtonian fluid flow in a catheterized arterial stenosis with slip condition at the wall of stenosed artery

R. Ponalagusamy 한국유변학회 2017 Korea-Australia rheology journal Vol.29 No.2

The primary concern of the present investigation is to study blood flow in a porous catheterized artery with an axially asymmetric and radially symmetric stenosis (constriction). In the present study, blood is characterized as a two-fluid system containing a cell-rich zone of suspension of blood cells described to be a particle-fluid suspension (Jeffrey fluid) and a cell-free plasma (Newtonian fluid) layer near the wall. The systematic expressions for flow characteristics such as fluid phase and particle phase velocities, flow rate, wall shear stress, resistive force, and frictional forces on walls of arterial stenosis and catheter are derived. It is recorded that the wall shear stress, flow resistance, and frictional forces are found to be increased with catheter size, red cell concentration, and slip parameter. When blood obeys the law of constitutive equation of a Jeffrey fluid, the flowing blood experiences lesser wall shear stress, flow resistance and frictional forces as compared to the case of blood being categorized as a Newtonian fluid. The increase in Darcy number, blood rheology as Jeffrey fluid, and the presence of peripheral plasma layer near the wall serves to reduce substantially the values of the flow characteristics (wall shear stress, flow resistance and frictional forces).

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.

여러가지 자기장 배치 기법에 따른 자성유체 속도 및 압력 분포에 관한 수치해석적 연구

송준호(Joon-Ho Song),이육형(Yuk-Hyung Lee),배형섭(Hyung-Sub Bae) 한국기계가공학회 2008 한국기계가공학회지 Vol.7 No.2

In this paper, we analyzed the dynamic behavior of magnetic fluid in a circular pipe with multiple permanent magnets. Magnetic fluid react on magnetic field against the normal fluid. In other words, magnetic fluid flow has the electromagnetism and fluid mechanics. So magnetic fluids has studied about the fluids properties and experiment. In this paper we studied the magnetic fluids velocity and pressure distribution for the novel type actuator. Because the velocity and pressure distribution is the important element of the magnetic fluids flow. First, we analyzed the Maxwell equation for the multiple permanent magnet and then concluded the governing equations for the magnetic fluid flow using the equation of Navier-Stokes. And, we simulated the dynamic behavior of magnetic fluid flow using the FEM(Finite Element Method). And we illustrated the relation between magnetic field and dynamic behavior of magnetic fluid flow.

Vortex generation by viscoelastic sheath flow in flow-focusing microchannel

김동영,김주민 한국화학공학회 2019 Korean Journal of Chemical Engineering Vol.36 No.6

Microfluidics-based technologies have attracted much attention since the fluid flow can be controlled precisely and only small sample volumes are required. Viscoelastic non-Newtonian fluids such as polymer solution and biofluids are frequently used in microfluidic analyses, and it is essential to understand the small-scale flow dynamics of such viscoelastic fluids. In this work, we report on vortex generation at the junction region of a flow-focusing microchannel, where a central flow stream of a Newtonian fluid meets two sheath flows of a non-Newtonian poly (ethylene oxide) aqueous solution. We elucidated the vortex-generation mechanism by the backward-flow component induced by the first normal stress difference in the viscoelastic sheath fluid. We systematically investigated the effects of polymer concentration, total flow rate, and total to central-stream flow-rate ratio, on the vortex generation. In addition, we demonstrated that this phenomenon can be engineered to enhance the mixing in the flow-focusing microchannel. We expect this work to be helpful for the understanding of viscoelastic flow dynamics in microscale flows and also for the development of microfluidic mixers.

Influence of slip velocity in Herschel-Bulkley fluid flow between parallel plates -A mathematical study

D. S. Sankar,Usik Lee 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.7

This theoretical study investigates three types of basic flows of viscous incompressible Herschel-Bulkley fluid such as (i) plane Couette flow, (ii) Poiseuille flow and (iii) generalized Couette flow with slip velocity at the boundary. The analytic solutions to the nonlinear boundary value problems have been obtained. The effects of various physical parameters on the velocity, flow rate, wall shear stress and frictional resistance to flow are analyzed through appropriate graphs. It is observed that in plane Poiseuille flow and generalized Couette flow, the velocity and flow rate of the fluid increase considerably with the increase of the slip parameter, power law index, pressure gradient. The fluid velocity is significantly higher in plane Poiseuille flow than in plane Couette flow. The wall shear stress and frictional resistance to flow decrease considerably with the increase of the power law index and increase significantly with the increase of the yield stress of the fluid. The wall shear stress and frictional resistance to flow are considerably higher in plane Poiseuille flow than in generalized Couette flow.