Effect of Pulsatile Flow Waveform and Womersley Number on the Flow in Stenosed Arterial Geometry

Abstract

The salient hemodynamic flow features in a stenosed artery depend not only on the degree of stenosis, but also on its location in the circulatory system and the physiological condition of the body. The nature of pulsatile flow waveform and local Womersley number vary in different regions of the arterial system and at different physiological state, which affects the local hemodynamic wall parameters, for example, the wall shear stress (WSS) and oscillatory shear index (OSI). Herein, we have numerically investigated the effects of different waveforms and Womersley numbers on the flow pattern and hemodynamic parameters in an axisymmetric stenosed arterial geometry with 50% diametral occlusion. Temporal evolution of the streamlines and hemodynamic parameters are investigated, and the time-averaged hemodynamic wall parameters are compared. Presence of the stenosis is found to increase the OSI of the flow even at the far-downstream side of the artery. At larger Womersley numbers, the instantaneous flow field in the stenosed region is found to have a stronger influence on the flow profiles of the previous time levels. The study delineates how an approximation in the assumption of inlet pulsatility profile may lead to significantly different prediction of hemodynamic wall parameters.

Numerical Simulation of Blood Flow in Double-Barreled Cannon EVAR and its Clinical Validation

“…This might explain why the arch swing reverse-flow signal disappeared in the DoBAR models. However, larger Womersley numbers have a stronger influence on the flow profiles in the stenotic region [10]. Therefore, the DoBAR models tended to stabilize the flow to a greater extent than the single stent-graft models.…”

“…Sometimes it is difficult to obtain experimental results from humans for ethical reasons, particularly when managing aortic surgery. For this reason, the computational fluid dynamic (CFD) method has been increasingly used to identify the best treatment strategy for humans, and is a useful tool for simulating the blood flow of the human aorta [8][9][10][11][12][13][14]. The CFD method can provide 3D numerical simulations of blood flow through an aortic model, providing for the identification of pathological mechanisms or the development of design changes in devices used in the aorta.…”

“…The moving blood forms a secondary flow pattern and develops into two counter-rotating vortices [9,5]. The strength (Q) of the secondary flow can be evaluated using (3): A dimensional analysis of the unsteady U-shaped pipe flow commonly leads to non-dimensional values for Re, for the Womersley number (α ), for the Strouhal number (St), and for the Dean number (De) [5,[9][10][11]. This study defined these parameters in (4) to (7), and used them to characterize the current unsteady blood vessel flow.…”

Multiple-Site Hemodynamic Analysis of Doppler Ultrasound with an Adaptive Color Relation Classifier for Arteriovenous Access Occlusion Evaluation

“…The Res index is defined as [26] $\begin{array}{c}\mathrm{Re}s=\frac{V_p-V_m}{V_p},\end{array}$ where V p is the peak-systolic velocity (PSV) and V m is the peak-diastolic velocity (PDV) through the Doppler ultrasound measurements. In the literatures [32], the cylindrical models with different diameters, viscosity, stroke displacement, and frequency were used to analyze flow instabilities. The critical peak Reynolds (Re peak ) number was derived at a power law to indicate the flow instabilities for in vitro studies.…”

Clinical important hemodynamic characteristics for serial stenosed coronary artery

“…A large number of studies computational [22][23][24][25][26][27] of the hemodynamics in diseased arteries exhibit disordered and turbulent flows in such vessels. Turbulence can significantly affect the pressure and shear stress downstream of the stenosis [28].…”