F154. Wall shear stress in a compliant aortic bifurcation model: Effect of phase angle between pressure and flow waves

Biorheology ◽  
1995 ◽  
Vol 32 (2-3) ◽  
pp. 308-308
Author(s):  
C LEE ◽  
J BARBELL
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Phase Angle ◽  
Aortic Bifurcation ◽  
Wall Shear ◽  
Pressure And Flow Waves

A 3D-LDA Study of the Relation Between Wall Shear Stress and Intimal Thickness in a Human Aortic Bifurcation

1996 ◽  
Vol 118 (3) ◽  
pp. 273-279 ◽  
Author(s):  
Kozaburo Hayashi ◽  
Yutaka Yanai ◽  
Takeru Naiki
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Blood Vessel ◽  
Newtonian Fluid ◽  
Shear Stresses ◽  
Elastic Model ◽  
Aortic Bifurcation ◽  
Local Flow ◽  
Intimal Thickness ◽  
Wall Shear

A realistic model experiment on hemodynamics was performed to study correlations between wall shear stresses measured in a cast model of the aortic bifurcation and intimal thickness at each corresponding site of the native blood vessel from which the cast had been made. An elastic model of a 54 year old human aortic bifurcation was made of a polyurethane elastomer using a dipping method, and was perfused with Newtonian or non-Newtonian fluid under physiologic pulsatile flow condition. Local flow velocities were measured with an optical-fibered, 3-dimensional laser Doppler anemometer (3D-LDA) to determine wall shear stresses. Distribution of intimal thickness was determined using histological specimens of the native blood vessel. The results obtained are: 1) Non-Newtonian fluid rheology increased wall shear stresses; 2) Positive correlations were observed between intimal thickness and the maximum instantaneous wall shear stress, and 3) However, if we take only the data from the circumference at the level of the flow divider tip, there were negative correlations between them.

scholarly journals Numerical Study of Non-Newtonian Blood Behavior in the Abdominal Aortic Bifurcation of a Patient-Specific at Rest

2017 ◽  
Vol 10 (1) ◽  
pp. 279-285 ◽  
Author(s):  
Carlos Oliveira ◽  
Armando A. Soares ◽  
André Simões ◽  
Sílvia Gonzaga ◽  
Abel Rouboa
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Cardiovascular Health ◽  
Numerical Study ◽  
Shear Thinning ◽  
Patient Specific ◽  
Aortic Bifurcation ◽  
Low Velocity ◽  
Abdominal Aortic ◽  
Wall Shear

Background:The interaction of blood flow with walls of blood vessels is central for the development and maintenance of cardiovascular health. The analysis of wall shear stress is, therefore, fundamental in hemodynamic studies.Objective:The aim of this work is to study numerically the influence of the shear thinning blood properties on the hemodynamics in the abdominal aortic bifurcation for a patient-specific at rest.Methods:Were tested two models for the blood dynamic viscosity, one Newtonian and other non-Newtonian, with dependence on hematocrit and total protein minus albumin.Results and Conclusion:The results show the shear thinning behavior influence on the velocity distribution and wall shear stress. Furthermore, wall shear stress values are globally lower for non-Newtonian blood model at high velocity values than those for the Newtonian blood model. However, for low velocity values this behavior is inverted.

scholarly journals Stress phase angle depicts differences in coronary artery hemodynamics due to changes in flow and geometry after percutaneous coronary intervention

2009 ◽  
Vol 296 (3) ◽  
pp. H765-H776 ◽  
Author(s):  
Ryo Torii ◽  
Nigel B. Wood ◽  
Nearchos Hadjiloizou ◽  
Andrew W. Dowsey ◽  
Andrew R. Wright ◽  
...  
Keyword(s):  
Shear Stress ◽  
Percutaneous Coronary Intervention ◽  
Wall Shear Stress ◽  
Phase Angle ◽  
Coronary Intervention ◽  
Oscillatory Shear Index ◽  
Percutaneous Coronary ◽  
Before And After ◽  
Wall Shear ◽  
Stress Phase Angle

The effects of changes in flow velocity waveform and arterial geometry before and after percutaneous coronary intervention (PCI) in the right coronary artery (RCA) were investigated using computational fluid dynamics. An RCA from a patient with a stenosis was reconstructed based on multislice computerized tomography images. A nonstenosed model, simulating the same RCA after PCI, was also constructed. The blood flows in the RCA models were simulated using pulsatile flow waveforms acquired with an intravascular ultrasound-Doppler probe in the RCA of a patient undergoing PCI. It was found that differences in the waveforms before and after PCI did not affect the time-averaged wall shear stress and oscillatory shear index, but the phase angle between pressure and wall shear stress on the endothelium, stress phase angle (SPA), differed markedly. The median SPA was −63.9° (range, −204° to −10.0°) for the pre-PCI state, whereas it was 10.4° (range, −71.1° to 25.4°) in the post-PCI state, i.e., more asynchronous in the pre-PCI state. SPA has been reported to influence the secretion of vasoactive molecules (e.g., nitric oxide, PGI2, and endothelin-1), and asynchronous SPA (≈−180°) is proposed to be proatherogenic. Our results suggest that differences in the pulsatile flow waveform may have an important influence on atherogenesis, although associated with only minor changes in the time-averaged wall shear stress and oscillatory shear index. SPA may be a useful indicator in predicting sites prone to atherosclerosis.

A Novel Computational Approach for Modeling Stent Reconstructing of an Aortic Bifurcation

2006 ◽  
Author(s):  
Ross Miller ◽  
Francine Battaglia
Keyword(s):  
Fluid Dynamics ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Numerical Models ◽  
Three Dimensional ◽  
Computational Approach ◽  
Aortic Bifurcation ◽  
Flow Phenomena ◽  
Novel Method ◽  
Wall Shear

Stent reconstruction of the aorta-iliac bifurcation was studied using computational fluid dynamics. Stents were modeled using a novel method, whereby the stents were represented as porous media. Three-dimensional numerical simulations using FLUENT were performed to determine how stent orientation affects the fluid dynamics. Three cases were studied and compared for both iliacs unstented, one iliac stented, and both iliacs stented. The stents lowered wall shear stress along the stented artery walls as compared to the unstented aorta-iliac model. However, the stent presence elevated vorticity, both in magnitude and size of the region. Additional studies were conducted to determine the effects for stent mis-alignment, where one stent protruded more into the aorta. It was found that when the stents were misaligned, wall shear stress increased near the stent inlet for the stent further inserted into the iliac. The resulting flow phenomena were consistent with other numerical models and medical investigations of stent reconstruction.

Numerical Analysis of Flow in an Elastic Artery Model

1992 ◽  
Vol 114 (1) ◽  
pp. 26-33 ◽  
Author(s):  
A. Dutta ◽  
D. M. Wang ◽  
J. M. Tarbell
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Phase Angle ◽  
Arterial Disease ◽  
Local Flow ◽  
Elastic Tubes ◽  
Pulsatile Flows ◽  
Wall Shear ◽  
Phase Angles ◽  
First Time

Oscillatory and pulsatile flows of Newtonian fluids in straight elastic tubes are simulated numerically with the aid of Ling and Atabek’s “local flow” assumption for the nonlinear convective acceleration terms. For the first time, a theoretical assessment of the local flow assumption is presented, and the range of validity of the assumption is estimated by comparison with perturbation solutions of the complete flow problem. Subsequent simulations with the local flow model indicate that the flow field and associated wall shear stress are extremely sensitive to the phase angle between oscillatory pressure and flow waves (impedance phase angle). This phase angle, which is a measure of the wave reflection present in the system, is known to be altered by arterial disease (e.g., hypertension) and vasoactive drugs. Thus, the paper elucidates a mechanism by which subtle changes in systemic hemodynamics (i.e., phase angles) can markedly influence local wall shear stress values.

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