A Simple Transient Poiseuille-Based Approach to Mimic the Womersley Function and to Model Pulsatile Blood Flow

As it is known, the Womersley function models velocity as a function of radius and time. It has been widely used to simulate the pulsatile blood flow through circular ducts. In this context, the present study is focused on the introduction of a simple function as an approximation of the Womersley function in order to evaluate its accuracy. This approximation consists of a simple quadratic function, suitable to be implemented in most commercial and non-commercial computational fluid dynamics codes, without the aid of external mathematical libraries. The Womersley function and the new function have been implemented here as boundary conditions in OpenFOAM ESI software (v.1906). The discrepancy between the obtained results proved to be within 0.7%, which fully validates the calculation approach implemented here. This approach is valid when a simplified analysis of the system is pointed out, in which flow reversals are not contemplated.

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Comparative Study of Blood Flow Through Normal, Stenosis Affected and Bypass Grafted Artery Using Computational Fluid Dynamics

Intelligent Computing & Optimization - Lecture Notes in Networks and Systems ◽

10.1007/978-3-030-93247-3_50 ◽

2022 ◽

pp. 503-512

Author(s):

Anirban Banik ◽

Tarun Kanti Bandyopadhyay ◽

Vladimir Panchenko

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Blood Flow ◽

Comparative Study ◽

Flow Through

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Computational fluid dynamics-based study of possibility of generating pulsatile blood flow via a continuous-flow VAD

Medical & Biological Engineering & Computing ◽

10.1007/s11517-016-1523-8 ◽

2016 ◽

Vol 55 (1) ◽

pp. 167-178 ◽

Cited By ~ 7

Author(s):

Erfan Nammakie ◽

Hanieh Niroomand-Oscuii ◽

Mojtaba Koochaki ◽

Farzan Ghalichi

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Blood Flow ◽

Continuous Flow ◽

Pulsatile Blood Flow

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Use of Computational Fluid Dynamics for the Replication of Clinical Blood Flow and Pressure Measurements and Characterization of Hemodynamics in the Normal Ascending and Thoracic Aorta

ASME 2007 Summer Bioengineering Conference ◽

10.1115/sbc2007-176447 ◽

2007 ◽

Author(s):

John F. LaDisa ◽

C. Alberto Figueroa ◽

Irene E. Vignon-Clementel ◽

Frandics P. Chan ◽

Jeffrey A. Feinstein ◽

...

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Blood Flow ◽

Boundary Conditions ◽

Thoracic Aorta ◽

Vascular Anatomy ◽

Data Set ◽

Cfd Models ◽

Computational Fluid Dynamics Cfd

Complications associated with abnormalities of the ascending and thoracic aorta are directly influenced by mechanical forces. To understand hemodynamic alterations associated with diseases in this region, however, we must first characterize related indices during normal conditions. Computational fluid dynamics (CFD) models of the ascending and thoracic aorta to date have only provided descriptions of the velocity field using idealized representations of the vasculature, a single patient data set, and outlet boundary conditions that do not replicate physiologic blood flow and pressure. Importantly, the complexity of aortic flow patterns, limited availability of methods for implementing appropriate boundary conditions, and ability to replicate vascular anatomy all contribute to the difficulty of the problem and, likely, the scarcity of more detailed studies.

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Abstract 99: Computational Fluid Dynamics of CT Angiography in SAMMPRIS Reveal Blood Flow and Vessel Interactions in Middle Cerebral Artery Stenoses

Stroke ◽

10.1161/str.47.suppl_1.99 ◽

2016 ◽

Vol 47 (suppl_1) ◽

Author(s):

David S Liebeskind ◽

Fabien Scalzo ◽

Graham W Woolf ◽

Justin M Zubak ◽

George A Cotsonis ◽

...

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Blood Flow ◽

Boundary Conditions ◽

Middle Cerebral Artery ◽

Ct Angiography ◽

Cerebral Artery ◽

Intraluminal Pressure ◽

Intracranial Atherosclerosis ◽

Fractional Flow

Background: Noninvasive fractional flow measures with CT angiography (CTA) have revolutionized cardiology, yet the complex anatomy of the cerebral circulation and boundary conditions challenge the study of intracranial atherosclerosis. We developed a framework for systematic computational fluid dynamics (CFD) of middle cerebral artery (MCA) stenosis with CTA in SAMMPRIS. Methods: A 3D geometric mesh was generated from CTA source images, followed by CFD processing in Ansys (ICEM, CFX) on a Cray supercomputer. Reference boundary conditions were applied with an ICA inlet and outlets at the ACA and distal MCA to yield quantitative maps of intraluminal pressure drops (ΔP or fractional flow), blood flow velocity (V) and turbulent kinetic energy (TKE) with wall shear stress (WSS) mapped along the arteries. CFD parameters were then compared with SAMMPRIS angiography variables. Results: Of 451 SAMMPRIS (70-99% symptomatic stenosis) subjects, CTA was acquired at enrollment in 41 MCA cases. CFD results were successfully attained in 30, limited by anatomy (e.g. across branch points) in 7/11 and poor CTA resolution in 4/11. Fractional flow (ΔP) across stenosis was mean 0.64 ± SD 0.33, with maximal stenosis velocity of mean 192 ± SD 101 cm/s and maximal WSS 0.36 ± SD 0.25 mm Hg. SAMMPRIS angiography percent stenosis was unrelated to ΔP -0.163 (p=0.399), velocity 0.126 (p=0.514) or WSS 0.078 (p=0.689). Worse collateral blood flow grades were associated with larger ΔP (p=0.137), higher velocity (p=0.059), higher WSS (p=0.112). Asymmetric WSS with high and low regions on opposing arterial walls was measured in the post-stenotic segment in 25/30 (83%). TKE maps revealed focal increases in the post-stenotic region, yet not above abnormal thresholds based on arterial diameter. Conclusions: CTA CFD of intracranial atherosclerosis provides detailed noninvasive measures of hemodynamics.

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Assessing Near-Wall Hemodynamics of Blood Flow in the Left Anterior Descending Segment of the Left Coronary Artery Using Computational Fluid Dynamics

Volume 3: Biomedical and Biotechnology Engineering ◽

10.1115/imece2017-71432 ◽

2017 ◽

Author(s):

John J. Asiruwa ◽

Aaron M. Propst ◽

Stephen P. Gent

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Blood Flow ◽

Shear Stress ◽

Coronary Artery ◽

Boundary Conditions ◽

Left Coronary Artery ◽

Pulsatile Mass ◽

Relative Residence Time ◽

Near Wall

The objective of this study was to computationally investigate the flow mechanics and the near-wall hemodynamics associated with the different take-off angles in the left coronary artery of the human heart. It is hypothesized that increasing the take-off angles of the left coronary artery will significantly increase or decrease the likelihood of plaque (atherosclerosis) buildup in the left coronary artery bifurcations. Specifically, this study quantified the effects of the varying take-off angles on the branches along the left anterior descending (LAD) of the left coronary artery using computational fluid dynamics (CFD) simulations. The study compared five test cases of the different take off-angles of the left coronary artery (LCA) and four different branch angles between the LAD and the left circumflex (LCx). It also considered the branch angles of the coronary artery downstream the LAD. The LCA inlet boundary conditions was set as a pulsatile mass flow inlet and flow split ratios were set for the outlets boundary conditions. The nature of blood pulsatile flow characteristic was accounted for and the properties of blood which include the density (1,050 kg/m3) and dynamic viscosity (0.0046 Pa-s) were obtained from previous research. The results from the simulations are compared using established scales for the parameters evaluated. The parameters evaluated were: (i) Oscillatory Shear Index (OSI); which quantifies the extent in which the blood flow changes direction during a cardiac cycle (ii) Time Average Wall Shear Stress (TAWSS); which quantifies the average shear stress experienced by the wall of the artery and (iii) Relative Residence Time (RRT); which quantifies how long blood spends in a location along the artery during blood flow. These parameters are used to predict the likelihood of blood clots, atherosclerosis, endothelial damage, plaque formation, and aneurysm in the blood vessels. The data from the simulations were analyzed using functional macros to quantify and generate threshold values for the parameters.

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