Evolution of vortical structures in a curved artery model with non-Newtonian blood-analog fluid under pulsatile inflow conditions

Najjari, Mohammad Reza; Plesniak, Michael W.

doi:10.1007/s00348-016-2188-7

Cited by 26 publications

(21 citation statements)

References 45 publications

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“…The velocity of the streamwise flow is skewed towards the inner wall of the vessel. This result agrees well with various other studies such as [ 40 , 85 – 88 ], which have observed reversed and skewed flow along the inner wall of the vessel. Although a direct validation of our simulation cannot be performed due to lack of availability of patient velocity data, the qualitative features from our simulations match well with previous aortic flow studies as indicated above.…”

Section: Resultssupporting

confidence: 93%

The effect of inlet and outlet boundary conditions in image-based CFD modeling of aortic flow

Madhavan

Kemmerling

2018

BioMed Eng OnLine

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BackgroundComputational modeling of cardiovascular flow is a growing and useful field, but such simulations usually require the researcher to guess the flow’s inlet and outlet conditions since they are difficult and expensive to measure. It is critical to determine the amount of uncertainty introduced by these assumptions in order to evaluate the degree to which cardiovascular flow simulations are accurate. Our work begins to address this question by examining the sensitivity of flow to several different assumed velocity inlet and outlet conditions in a patient-specific aorta model.MethodsWe examined the differences between plug flow, parabolic flow, linear shear flows, skewed cubic flow profiles, and Womersley flow at the inlet. Only the shape of the inlet velocity profile was varied—all other parameters were identical among these simulations. Secondary flow in the form of a counter-rotating pair of vortices was also added to parabolic axial flow to study its effect on the solution. In addition, we examined the differences between two-element Windkessel, three element Windkessel and the outflow boundary conditions. In these simulations, only the outlet boundary condition was varied.ResultsThe results show axial and in-plane velocities are considerably different close to the inlet for the cases with different inlet velocity profile shapes. However, the solutions are qualitatively similar beyond 1.75D, where D is the inlet diameter. This trend is also observed in other quantities such as pressure and wall shear stress. Normalized root-mean-square deviation, a measure of axial velocity magnitude differences between the different cases, generally decreases along the streamwise coordinate. The linear shear inlet velocity boundary condition and plug velocity boundary condition solution exhibit the highest time-averaged wall shear stress, approximately higher than the parabolic inlet velocity boundary condition. Upstream of 1D from the inlet, adding secondary flow has a significant impact on temporal wall shear stress distributions. This is especially observable during diastole, when integrated wall shear stress magnitude varies about between simulations with and without secondary flow. The results from the outlet boundary condition study show the Windkessel models differ from the outflow boundary condition by as much as in terms of time-averaged wall shear stress. Furthermore, normalized root-mean-square deviation of axial velocity magnitude, a measure of deviation between Windkessel and the outflow boundary condition, increases along the streamwise coordinate indicating larger variations near outlets.ConclusionIt was found that the selection of inlet velocity conditions significantly affects only the flow region close to the inlet of the aorta. Beyond two diameters distal to the inlet, differences in flow solution are small. Although additional studies must be performed to verify this result, the data suggest that it is important to use patient-specific inlet conditions primarily if the researcher is concerned wit...

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Section: Resultssupporting

confidence: 93%

The effect of inlet and outlet boundary conditions in image-based CFD modeling of aortic flow

Madhavan

Kemmerling

2018

BioMed Eng OnLine

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“…Under pulsatile (physiological) inflow conditions, Chang and Tarbell (1985) observed secondary vortices similar to those found by Lyne. According to more-recent fluid dynamical studies of physiological flows (van Wyk et al, 2015;Najjari and Plesniak, 2016), the secondary flow consists of multiple vortices as well as the Dean and Lyne types with the temporal evolution of vortical structures. Furthermore, in unsteady laminar flow, as well as the secondary radial flow, the axial flow (in the axial direction of the pipe) also exhibits behavior that differs from the steady case, even if the pipe geometry does not vary axially.…”

Section: Introductionmentioning

confidence: 99%

Stereo and time-resolved PIV for measuring pulsatile exhaust flow from a motorized engine

Oki

Kuga

Ogata

et al. 2018

JFST

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The present experimental study deals with a pulsatile turbulent flow simulating the exhaust flow of an automotive engine. In the experiments, a four-cylinder engine is used as an exhaust-flow generator to realize flow conditions close to those in an engine environment. Particle image velocimetry (PIV) measurements visualize the flow field in an S-shaped double-bend duct at a Reynolds number of 48,000 and a Womersley number of 70.9. Stereo PIV, which is classified as a two-dimensional three-component measurement, is conducted in the duct cross sections located downstream of the bends. The stereo PIV system is synchronized with the engine operation to enable phase-locked measurements at particular phases, and the phase-averaged results show the large-scale vortical structures and the duct axial velocity distribution. Downstream of the first bend, the secondary flow consists of vortices that circulate as Dean-type vortices. Downstream of the second bend, by contrast, vortices that circulate in opposite directions to the Dean-type vortices, so-called Lyne-type vortices, form in the core of the cross section. These secondary flows persist without significant changes in their large-scale vortical structures over time. Time-resolved PIV is conducted to track the temporal evolution of the flow in the bend planes. The results show that the flow reverses locally along the inner wall of the bends during flow deceleration. Snapshot proper orthogonal decomposition (POD) is used on the time-resolved PIV data to extract the significant flow structure from the instantaneous field. We propose POD as a good post-processing tool for the instantaneous data of pulsatile cases.

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“…A fully programmable commercial pump is CardioFlow (Shelley Medical Imaging Technologies, London, ON, Canada), which is again a two-sided piston pump that generates pulsatile flow, by dividing the cylinder into two chambers, each with fluid ports at the end. Some of the studies that utilize these pumps in hemodynamic analysis of different arteries are Pahlevan and Gharib (2013), Groves et al (2014), and Najjari and Plesniak (2016). Resulting waveforms for these commercial pumps are very similar to physiological cases of predefined arteries, but the range of arteries that they can replicate is limited.…”

Section: Experimental Investigation Of Hemodynamics Of Aaasmentioning

confidence: 99%

“…Most of the experimental studies utilize the Newtonian assumption, and generally pure water or the mixture of glycerin and water with different volumetric ratios have been widely used as blood mimicking fluid (Boutsianis et al, 2008; Stamatopoulos et al, 2010, 2011). There is only few studies that use non-Newtonian fluids of which behavior are very similar to the blood, like Xanthane Gum solution with glycerin (Deplano et al, 2014; Najjari and Plesniak, 2016).…”

Section: Experimental Investigation Of Hemodynamics Of Aaasmentioning

confidence: 99%

“…They conclude that the rheology of working fluid affects the hemodynamics inside aneurysm model, and should be taken into account for more realistic experimentation. On the other hand, in another study which is performed on a curved artery model with again a shear thinning fluid, mixture of fluids like Xanthane Gum, glycerin, water, and sodium iodide (Najjari and Plesniak, 2016). The results are very similar to the studies for curved arteries with Newtonian fluids, concluding that for large arteries with large flow rates, rheology of the blood does not affect the flow structure.…”

Section: Experimental Investigation Of Hemodynamics Of Aaasmentioning

confidence: 99%

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Biomechanical Investigation of Disturbed Hemodynamics-Induced Tissue Degeneration in Abdominal Aortic Aneurysms Using Computational and Experimental Techniques

Salman

Ramazanlı

Yavuz

et al. 2019

Front. Bioeng. Biotechnol.

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Abdominal aortic aneurysm (AAA) is the dilatation of the aorta beyond 50% of the normal vessel diameter. It is reported that 4–8% of men and 0.5–1% of women above 50 years of age bear an AAA and it accounts for ~15,000 deaths per year in the United States alone. If left untreated, AAA might gradually expand until rupture; the most catastrophic complication of the aneurysmal disease that is accompanied by a striking overall mortality of 80%. The precise mechanisms leading to AAA rupture remains unclear. Therefore, characterization of disturbed hemodynamics within AAAs will help to understand the mechanobiological development of the condition which will contribute to novel therapies for the condition. Due to geometrical complexities, it is challenging to directly quantify disturbed flows for AAAs clinically. Two other approaches for this investigation are computational modeling and experimental flow measurement. In computational modeling, the problem is first defined mathematically, and the solution is approximated with numerical techniques to get characteristics of flow. In experimental flow measurement, once the setup providing physiological flow pattern in a phantom geometry is constructed, velocity measurement system such as particle image velocimetry (PIV) enables characterization of the flow. We witness increasing number of applications of these complimentary approaches for AAA investigations in recent years. In this paper, we outline the details of computational modeling procedures and experimental settings and summarize important findings from recent studies, which will help researchers for AAA investigations and rupture mechanics.

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Evolution of vortical structures in a curved artery model with non-Newtonian blood-analog fluid under pulsatile inflow conditions

Cited by 26 publications

References 45 publications

The effect of inlet and outlet boundary conditions in image-based CFD modeling of aortic flow

The effect of inlet and outlet boundary conditions in image-based CFD modeling of aortic flow

Stereo and time-resolved PIV for measuring pulsatile exhaust flow from a motorized engine

Biomechanical Investigation of Disturbed Hemodynamics-Induced Tissue Degeneration in Abdominal Aortic Aneurysms Using Computational and Experimental Techniques

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