CFD Analysis Comparing Steady Flow and Pulsatile Flow Through the Aorta and its Main Branches

2016 ◽  
Author(s):  
John D. Martin
Keyword(s):  
Blood Flow ◽  
Steady Flow ◽  
Pulsatile Flow ◽  
Close Association ◽  
Beating Heart ◽  
Pressure Data ◽  
Heart Model ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Through ◽  
Very High

A computational fluid dynamics (CFD) study has been done comparing pulsatile and non-pulsatile blood flow through the aortic arch and its main branches. The pulsatile flow was to mimic the blood flow due to a beating heart and the non-pulsatile or steady flow was to mimic cardiopulmonary bypass (CPB). The purpose of the study was too narrow in on possible reasons CPB may contribute to the development of atherosclerosis. The main focus of the study was to look at the wall shear stress (WSS) values due to their close association with the development of atherosclerosis. In addition velocity and pressure data were also analyzed. The results of this study showed a stark contrast between the WSS values between the CPB model and the beating heart model. The CPB model did not have any points of oscillating WSS combined with the fact that there were regions of very high and very low constant WSS values in comparison with the beating heart analysis suggests that there may be potential for atherosclerotic development or plaque buildup within the artery. The beating heart model showed a range of WSS values within the aorta that were much lower overall compared with the CPB model.

Vortex Generation in Pulsatile Flow Through Arterial Bifurcation Models Including the Human Carotid Artery

1988 ◽  
Vol 110 (3) ◽  
pp. 166-171 ◽  
Author(s):  
Takayoshi Fukushima ◽  
Tatsuji Homma ◽  
Kiyohito Harakawa ◽  
Noriyuki Sakata ◽  
Takehiko Azuma
Keyword(s):  
Steady Flow ◽  
Pulsatile Flow ◽  
Separation Bubble ◽  
Vortex Formation ◽  
Flow Distribution ◽  
Horseshoe Vortex ◽  
Helical Flow ◽  
Elastic Tube ◽  
Recirculating Flow ◽  
Flow Through

Visualization experiments were performed to elucidate the complicated flow pattern in pulsatile flow through arterial bifurcations. Human common carotid arteries, which were made transparent, and glass-models simulating Y- and T-shaped bifurcations were used. Pulsatile flow with wave forms similar to those of arterial flow was generated with a piston pump, elastic tube, airchamber, and valves controlling the outflow resistance. Helically recirculating flow with a pattern similar to that of the horseshoe vortex produced around wall-based protuberances in circular tubes was observed in pulsatile flow through all the bifurcations used in the present study. This flow type, which we shall refer to as the horseshoe vortex, has also been demonstrated to occur at the human common carotid bifurcation in steady flow with Reynolds numbers above 100. Time-varying flows also produced the horseshoe vortex mostly during the decelerating phase. Fluid particles of dye solution approaching the bifurcation apex diverged, divided into two directions perpendicularly, and then showed helical motion representing the horseshoe vortex formation. While this helical flow was produced, the stagnation points appeared on the wall upstream of the apex. Their position was dependent upon the flow distribution ratio between the branches in the individual arteries. The region affected by the horseshoe vortex was smaller during pulsatile flow than during steady flow. Lowering the Reynolds number together with the Womersley number weakened the intensity of helical flow. A separation bubble, resulting from the divergence or wall roughness, was observed at the outer or inner wall of the branch vessels and made the flow more complicated.

scholarly journals Pulsatile Flow of a Two-Fluid Model for Blood Flow through Arterial Stenosis

2010 ◽  
Vol 2010 ◽  
pp. 1-26 ◽  
Author(s):  
D. S. Sankar
Keyword(s):  
Blood Flow ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Pulsatile Flow ◽  
Fluid Model ◽  
Core Radius ◽  
Flow Through ◽  
Wall Shear ◽  
Two Fluid Model ◽  
Two Fluid

Pulsatile flow of a two-fluid model for blood flow through stenosed narrow arteries is studied through a mathematical analysis. Blood is treated as two-phase fluid model with the suspension of all the erythrocytes in the as Herschel-Bulkley fluid and the plasma in the peripheral layer as a Newtonian fluid. Perturbation method is used to solve the system of nonlinear partial differential equations. The expressions for velocity, wall shear stress, plug core radius, flow rate and resistance to flow are obtained. The variations of these flow quantities with stenosis size, yield stress, axial distance, pulsatility and amplitude are analyzed. It is found that pressure drop, plug core radius, wall shear stress and resistance to flow increase as the yield stress or stenosis size increases while all other parameters held constant. It is observed that the percentage of increase in the magnitudes of the wall shear stress and resistance to flow over the uniform diameter tube is considerably very low for the present two-fluid model compared with that of the single-fluid model of the Herschel-Bulkley fluid. Thus, the presence of the peripheral layer helps in the functioning of the diseased arterial system.

Alternative method to evaluate discharge coefficients. Part 2: Case study

2008 ◽  
Vol 223 (3) ◽  
pp. 627-636
Author(s):  
R I Gault ◽  
D J Thornhill ◽  
R Fleck
Keyword(s):  
Steady Flow ◽  
Cfd Validation ◽  
Discharge Coefficients ◽  
Poppet Valve ◽  
Alternative Method ◽  
Engine Cylinder ◽  
Flow Apparatus ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Through

The purpose of this article is to apply an alternative method whereby discharge coefficients can be estimated for the flow through a poppet valve at various lifts. Presented is the development of an operational quasi-steady flow rig. An engine cylinder head poppet valve was used as the case study. The requirement to directly measure mass flowrates using a standard conventional steady flow apparatus has been eliminated. Transient mass flowrates, pressures and temperatures of air during an inflow test for a poppet valve at various lifts were measured. Mass flowrates were also calculated from measured cylinder gas pressures and corrected for heat transfer. Using both methods to determine the mass flowrates, isentropic discharge coefficients were calculated and shown to compare within>4.0 per cent of steady flow data. A computational fluid dynamics (CFD) validation of the quasi-steady flow rig is also presented.

Constant Blood Flow during Single-Needle Dialysis is Unnecessary

1993 ◽  
Vol 16 (7) ◽  
pp. 505-509 ◽  
Author(s):  
H.D. Polaschegg ◽  
R. Wojke
Keyword(s):  
Blood Flow ◽  
Vascular Access ◽  
Pulsatile Flow ◽  
Tidal Flow ◽  
Constant Flow ◽  
Pulsatile Blood Flow ◽  
Flow Rates ◽  
Flow Through ◽  
Optimal Efficiency

Single-needle (SN) dialysis employs tidal blood flow at the point of vascular access. The simplest SN systems convert this tidal flow to a pulsatile flow in the dialyser. It has been assumed that constant flow through the dialyser is necessary for optimal efficiency. Therefore SN blood circuits are designed to smooth the pulsatile flow in the dialyser to a relatively constant flow. This increases the complexity and cost of the SN system. In order to test the hypothesis that pulsatile flow results in lower clearances than constant flow, we performed measurements of clearance in vitro using pulsatile blood flow at time-averaged rates of 50-250 ml/min and tidal volumes 200-100 ml/min. These were compared with clearances using constant blood flow at the same rates. At all flow rates and at tidal volumes up to 50 ml, the clearance measurements obtained during pulsatile flow were identical to those obtained during constant flow.

NUMERICAL SIMULATION OF TRANSIENT BLOOD FLOW THROUGH THE LEFT CORONARY ARTERY WITH VARYING DEGREES OF BIFURCATION ANGLES

2017 ◽  
Vol 17 (01) ◽  
pp. 1750005
Author(s):  
BO ZHANG ◽  
YILUN JIN ◽  
XIAORAN WANG ◽  
TAISHENG ZENG ◽  
LIANSHENG WANG
Keyword(s):  
Blood Flow ◽  
Coronary Artery ◽  
Left Coronary Artery ◽  
Vascular System ◽  
Abdominal Aortic ◽  
Analysis Technique ◽  
Common Technique ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Through ◽  
The Relationship

Atherosclerosis is a cardiovascular condition that can occur in any part of the vascular system. Especially, it can exist in bifurcated arteries such as the left and right coronary arteries, abdominal aortic bifurcation or carotid artery bifurcation. In our study, we examine the left coronary artery as an exemplification using wall shear stress (WSS) and wall pressure gradient (WPG). Then, we attempt to find the relationship between bifurcated arterial geometry and hemodynamics. Computational fluid dynamics (CFD) is a common technique applied to characterize blood flow accurately and assist us to gain an insight of atherosclerosis. In this paper, we used CFD as the computational hemodynamics analysis technique to examine flow through the left coronary artery that has variable angular bifurcation. Our results demonstrated that the region of low WSS area and magnitudes of maximum WPG increases with the angles of bifurcation. Such hemodynamic condition resulting from the large bifurcation angles has an effect on atherogenesis and is worthy of investigation for better understanding of atherosclerosis.

Pulsatile Flow and Mass Transport Over an Array of Cylinders: Gas Transfer in a Cardiac-Driven Artificial Lung

2005 ◽  
Vol 128 (1) ◽  
pp. 85-96 ◽  
Author(s):  
Kit Yan Chan ◽  
Hideki Fujioka ◽  
Robert H. Bartlett ◽  
Ronald B. Hirschl ◽  
James B. Grotberg
Keyword(s):  
Pressure Drop ◽  
Steady Flow ◽  
Void Fraction ◽  
Pulsatile Flow ◽  
Fiber Bundle ◽  
Gas Transfer ◽  
Right Heart ◽  
Flow Through ◽  
The Right ◽  
Array Geometry

The pulsatile flow and gas transport of a Newtonian passive fluid across an array of cylindrical microfibers are numerically investigated. It is related to an implantable, artificial lung where the blood flow is driven by the right heart. The fibers are modeled as either squared or staggered arrays. The pulsatile flow inputs considered in this study are a steady flow with a sinusoidal perturbation and a cardiac flow. The aims of this study are twofold: identifying favorable array geometry/spacing and system conditions that enhance gas transport; and providing pressure drop data that indicate the degree of flow resistance or the demand on the right heart in driving the flow through the fiber bundle. The results show that pulsatile flow improves the gas transfer to the fluid compared to steady flow. The degree of enhancement is found to be significant when the oscillation frequency is large, when the void fraction of the fiber bundle is decreased, and when the Reynolds number is increased; the use of a cardiac flow input can also improve gas transfer. In terms of array geometry, the staggered array gives both a better gas transfer per fiber (for relatively large void fraction) and a smaller pressure drop (for all cases). For most cases shown, an increase in gas transfer is accompanied by a higher pressure drop required to power the flow through the device.

Pulsatile Flow in Tapered Tubes: A Model of Blood Flow With Large Disturbances

1983 ◽  
Vol 105 (2) ◽  
pp. 112-119 ◽  
Author(s):  
E. Kimmel ◽  
U. Dinnar
Keyword(s):  
Blood Flow ◽  
Pulsatile Flow ◽  
Mean Value ◽  
Navier Stokes ◽  
Shear Stresses ◽  
Pressure Gradients ◽  
Navier Stokes Equation ◽  
Rigid Tube ◽  
Flow Through ◽  
Uniform Tube

Blood flow-through segments of large arteries of man, between adjacent bifurcations, can be modeled as pulsatile flow in tapered converging tubes, of small angle of convergence, up to 2 deg. Assuming linearity, rigid tube and homogeneous Newtonian fluid, the physiological flow field is governed by the Navier-Stokes equation with dominant nonlinear and unsteady terms. Analytical solution of this problem is presented based on an integral method technique. The solution shows that even for small tapering the flow pattern is markedly different from the flow obtained for a uniform tube. The periodic shear stresses at the wall and pressure gradients increase both in their mean value and amplitude with increased distance downstream. These results are highly significant in the process of atherogenesis.

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