scholarly journals A numerical study of the effects of blood rheology and vessel deformability on the hemodynamics of carotid bifurcation

2012 ◽  
Vol 19 (1) ◽  
pp. 119-126 ◽  
Author(s):  
M. Toloui ◽  
B. Firoozabadi ◽  
M.S. Saidi
Keyword(s):  
Numerical Study ◽  
Blood Rheology ◽  
Carotid Bifurcation

Numerical study on the hemodynamics of patient-specific carotid bifurcation using a new mesh approach

2018 ◽  
Vol 34 (6) ◽  
pp. e2972 ◽  
Author(s):  
S.I.S. Pinto ◽  
J.B.L.M. Campos ◽  
E. Azevedo ◽  
C.F. Castro ◽  
L.C. Sousa
Keyword(s):  
Numerical Study ◽  
Carotid Bifurcation ◽  
Patient Specific

scholarly journals Numerical study on the energy cascade of pulsatile Newtonian and power-law flow models in an ICA bifurcation

PLoS ONE ◽  
2021 ◽  
Vol 16 (1) ◽  
pp. e0245775
Author(s):  
Samar A. Mahrous ◽  
Nor Azwadi Che Sidik ◽  
Khalid M. Saqr
Keyword(s):  
Reynolds Number ◽  
Power Law ◽  
Numerical Study ◽  
Carotid Bifurcation ◽  
Shear Thinning ◽  
Energy Cascade ◽  
Hemodynamic Parameters ◽  
Vortex Identification ◽  
Newtonian Viscosity ◽  
The Impact

The complex physics and biology underlying intracranial hemodynamics are yet to be fully revealed. A fully resolved direct numerical simulation (DNS) study has been performed to identify the intrinsic flow dynamics in an idealized carotid bifurcation model. To shed the light on the significance of considering blood shear-thinning properties, the power-law model is compared to the commonly used Newtonian viscosity hypothesis. We scrutinize the kinetic energy cascade (KEC) rates in the Fourier domain and the vortex structure of both fluid models and examine the impact of the power-law viscosity model. The flow intrinsically contains coherent structures which has frequencies corresponding to the boundary frequency, which could be associated with the regulation of endothelial cells. From the proposed comparative study, it is found that KEC rates and the vortex-identification are significantly influenced by the shear-thinning blood properties. Conclusively, from the obtained results, it is found that neglecting the non-Newtonian behavior could lead to underestimation of the hemodynamic parameters at low Reynolds number and overestimation of the hemodynamic parameters by increasing the Reynolds number. In addition, we provide physical insight and discussion onto the hemodynamics associated with endothelial dysfunction which plays significant role in the pathogenesis of intracranial aneurysms.

scholarly journals Numerical study on thoracic aortic aneurysms : the aneurysms aggravation effects on the seconda rythme flows motion

Mechanika ◽  
2020 ◽  
Vol 26 (5) ◽  
pp. 407-415
Author(s):  
Mohammed Ilies ARAB ◽  
Mohamed BOUZIT ◽  
Houari AMEUR ◽  
Youcef KAMLA
Keyword(s):  
Vortex Ring ◽  
Vascular System ◽  
Numerical Study ◽  
Blood Rheology ◽  
Aortic Aneurysms ◽  
Hydrodynamic Instabilities ◽  
Thoracic Aortic Aneurysms ◽  
Secondary Motion ◽  
Ring Interaction ◽  
Ring Phenomenon

It is Well know  that there is a strong correlation between artery wall diseases and the flow structure disturbance. Aneurysms are enlargements situated at different but specifics parts of the vascular system; it is a silent diseas that evolves in time. The thoracic aortic aneurysms  (T. A. A) remains relatively unstudied and therefore the present study aimis is to clarify the effects of the  (T . A. A) evolution and the geometrical variations on both hydrodynamic instabilities inside the aortic bulge especially the vortex ring phenomenon and the secondary motion (Dean and lyne vortices) downsream the aneurysms.  Two different cases of asymmetric enlargements in the ascending part of the aortic are studied for both newtonien and the shear-thinning model to mimic the blood rheology inside the aneurysms bulge in order to investigate both parameters impact on the vortex ring behavior. Results schowed that the blood rheoligy effects the propagation velocity while the aneurysms size influences the vortex ring rupture,  the motion of the ring interaction with an inclined wall phenomenon. Results also showed that vortex ring disturbs the boundary layer and therefore the secondary motion in the rest of the aorta.

Numerical study for blood rheology inside an artery: The effects of stenosis and radius on the flow behavior

2020 ◽  
Vol 193 ◽  
pp. 105457 ◽  
Author(s):  
Loke Kok Foong ◽  
Majid Zarringhalam ◽  
Davood Toghraie ◽  
Niloufar Izadpanahi ◽  
Shu-Rong Yan ◽  
...  
Keyword(s):  
Numerical Study ◽  
Flow Behavior ◽  
Blood Rheology

Effects of Blood Rheology on Flow Topology and Blood-Vessel Interaction in Image-Based Carotid Bifurcation Numerical Model

2009 ◽  
Author(s):  
Diana Massai ◽  
Raffaele Ponzini ◽  
Diego Gallo ◽  
Luca Antiga ◽  
Giuseppe Passoni ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Blood Rheology ◽  
Helical Structure ◽  
Carotid Bifurcation ◽  
Helical Flow ◽  
Bulk Flow ◽  
Vascular Pathology ◽  
Flow Index ◽  
Flow Topology ◽  
Adopted Model

In recent years, interest is growing on compact measures for assessing the role of local hemodynamics in the pathogenesis of atherosclerosis and atherogenesis. CFD and its power in evaluating and predicting the effect of some hemodynamic variables in vascular disease is becoming a key factor in clinical research. Recently, Lee and Steinman [1] assessed the importance of blood rheology assumptions to ascertain the effect of constitutive relation for blood on local wall shear stress (WSS) and on the correlated vascular pathology. We present a preliminary in silico investigation on the sensitivity of helical flow measure with respect to the blood constitutive adopted model. Our main objective was to verify if, through the carotid bifurcation model, the rheological properties of blood significantly influence the bulk flow topology, whose evolution and stability are strictly linked to helicity. In fact helicity — an invariant in fluid dynamics — has been demonstrated to describe and reveal the global organization in a fluid flow. For this purpose several blood models (Newtonian and non-Newtonian) were implemented. A specific Lagrangian-based “bulk” flow descriptor, the Helical Flow Index (HFI) [2], was calculated in order to get a “measure” of the helical structure in the blood flow. Therefore, its sensitivity to blood rheology and hematocrit (Ht) was assessed and compared with the sensitivity of WSS based on other fluid dynamics descriptors (Time Averaged WSS, TAWSS, and Oscillating Shear Index, OSI).

INTIMAL HYPERPLASIA AND WALL SHEAR IN ARTERIAL BYPASS Y-GRAFTING AND CONSEQUENCE GRAFTING: A NUMERICAL STUDY

2014 ◽  
Vol 14 (03) ◽  
pp. 1450044 ◽  
Author(s):  
HUNG DO ◽  
AMAL A. OWIDA ◽  
YOSRY S. MORSI
Keyword(s):  
Intimal Hyperplasia ◽  
Numerical Study ◽  
Blood Rheology ◽  
Surface Characteristics ◽  
Flow Patterns ◽  
Dean Flow ◽  
Hemodynamic Forces ◽  
Internal Mammary ◽  
The Individual ◽  
Hemodynamic Flow

The progression of intimal hyperplasia is considered to be the main cause of bypass failure and is directly related to the individual blood rheology, local arterial geometry and placement of the junctions, graft diameter and graft surface characteristics as well as the degree of compliance. In this paper we use commercial computational fluid dynamics (CFD) ANSYS to examine under the correct physiological flow conditions the hemodynamic forces of composite bypass with internal mammary artery in Y-grafting and consequence grafting which is known to achieve high patency rate and highly recommended by clinicians. Particular emphasis is given here on the parameters that could initiate the development of intimal hyperplasia within these bypass configurations. The hemodynamic flow patterns between the consequence grafting and the composite Y-grafting are observed here to be different. Moreover, on both end-to-side and side-to-side configurations, the circulating flows are detected in the vicinity of the junction area, while the Dean flow vortexes are only observed on the end-to-side configuration. Likewise, the hemodynamic flow on the end-to-side configuration on the LCX of both 45° and 90° Y-grafting is found to be smoother than that of the junction on the LCA, regardless of the changing of anastomosis angles. The high WSS gradients are observed at the vicinity of the toe and on the bed of the junction, while the low WSS are presented at the distal of the stenosis and at the stagnation point. The clinical relevance of the results are presented and discussed with particular focus on the factors and the flow patterns that trigger the development of intimal hyperplasia.

On the Relative Importance of Rheology for Image-Based CFD Models of the Carotid Bifurcation

2006 ◽  
Vol 129 (2) ◽  
pp. 273-278 ◽  
Author(s):  
Sang-Wook Lee ◽  
David A. Steinman
Keyword(s):  
Blood Rheology ◽  
Carotid Bifurcation ◽  
Patient Specific ◽  
Newtonian Viscosity ◽  
Cfd Simulations ◽  
Shear Rates ◽  
Cfd Models ◽  
Geometric Precision ◽  
Simplifying Assumptions ◽  
Constant Viscosity

Background: Patient-specific computational fluid dynamics (CFD) models derived from medical images often require simplifying assumptions to render the simulations conceptually or computationally tractable. In this study, we investigated the sensitivity of image-based CFD models of the carotid bifurcation to assumptions regarding the blood rheology. Method of Approach: CFD simulations of three different patient-specific models were carried out assuming: a reference high-shear Newtonian viscosity, two different non-Newtonian (shear-thinning) rheology models, and Newtonian viscosities based on characteristic shear rates or, equivalently, assumed hematocrits. Sensitivity of wall shear stress (WSS) and oscillatory shear index (OSI) were contextualized with respect to the reproducibility of the reconstructed geometry, and to assumptions regarding the inlet boundary conditions. Results: Sensitivity of WSS to the various rheological assumptions was roughly 1.0dyn∕cm2 or 8%, nearly seven times less than that due to geometric uncertainty (6.7dyn∕cm2 or 47%), and on the order of that due to inlet boundary condition assumptions. Similar trends were observed regarding OSI sensitivity. Rescaling the Newtonian viscosity based on time-averaged inlet shear rate served to approximate reasonably, if overestimate slightly, non-Newtonian behavior. Conclusions: For image-based CFD simulations of the normal carotid bifurcation, the assumption of constant viscosity at a nominal hematocrit is reasonable in light of currently available levels of geometric precision, thus serving to obviate the need to acquire patient-specific rheological data.

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