Limits...
Fluid-dynamic optimal design of helical vascular graft for stenotic disturbed flow.

Ha H, Hwang D, Choi WR, Baek J, Lee SJ - PLoS ONE (2014)

Bottom Line: Results showed that the swirling intensity and helicity of the swirling flow have a linear relation with a modified Germano number (Gn*) of the helical pipe.In addition, the swirling flow generated a beneficial flow structure at the stenosis by reducing the size of the recirculation flow under steady and pulsatile flow conditions.Therefore, the beneficial effects of a helical graft on the flow field can be estimated by using the magnitude of Gn*.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk, Republic of Korea.

ABSTRACT
Although a helical configuration of a prosthetic vascular graft appears to be clinically beneficial in suppressing thrombosis and intimal hyperplasia, an optimization of a helical design has yet to be achieved because of the lack of a detailed understanding on hemodynamic features in helical grafts and their fluid dynamic influences. In the present study, the swirling flow in a helical graft was hypothesized to have beneficial influences on a disturbed flow structure such as stenotic flow. The characteristics of swirling flows generated by helical tubes with various helical pitches and curvatures were investigated to prove the hypothesis. The fluid dynamic influences of these helical tubes on stenotic flow were quantitatively analysed by using a particle image velocimetry technique. Results showed that the swirling intensity and helicity of the swirling flow have a linear relation with a modified Germano number (Gn*) of the helical pipe. In addition, the swirling flow generated a beneficial flow structure at the stenosis by reducing the size of the recirculation flow under steady and pulsatile flow conditions. Therefore, the beneficial effects of a helical graft on the flow field can be estimated by using the magnitude of Gn*. Finally, an optimized helical design with a maximum Gn* was suggested for the future design of a vascular graft.

Show MeSH

Related in: MedlinePlus

Variations of swirling intensity (S) with respect to Gn*.(a) Effect of Re on swirling intensity variation, (b) a linear regression curve (S = 0.0004×Gn*–0.0075, R2 = 0.834) and 95% confidence and prediction bands.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4215892&req=5

pone-0111047-g010: Variations of swirling intensity (S) with respect to Gn*.(a) Effect of Re on swirling intensity variation, (b) a linear regression curve (S = 0.0004×Gn*–0.0075, R2 = 0.834) and 95% confidence and prediction bands.

Mentions: The variations of swirling intensities obtained at all helical curvatures and pitches were analysed with the modified Germano number Gn* (figure 10). Regardless of Re, all S values are well overlapped and increase in proportion to Gn* (figure 10a). The linear regression line at 95% confidence and prediction bands (figure 10b) shows that S = 0.0004×Gn* − 0.0075 with R2 = 0.834. Helicity, an alternative parameter of S, also shows a linear increment with Gn*. The slopes of the helicity increment are dependent on Re (figure 11). The slopes of the linear regression are 2.15×10−7 (Re = 213, R2 = 0.859), 4.47×10−7 (Re = 410, R2 = 0.879), 5.22×10−7 (Re = 609, R2 = 0.896) and 9.82×10−7 (Re = 814, R2 = 0.838).


Fluid-dynamic optimal design of helical vascular graft for stenotic disturbed flow.

Ha H, Hwang D, Choi WR, Baek J, Lee SJ - PLoS ONE (2014)

Variations of swirling intensity (S) with respect to Gn*.(a) Effect of Re on swirling intensity variation, (b) a linear regression curve (S = 0.0004×Gn*–0.0075, R2 = 0.834) and 95% confidence and prediction bands.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4215892&req=5

pone-0111047-g010: Variations of swirling intensity (S) with respect to Gn*.(a) Effect of Re on swirling intensity variation, (b) a linear regression curve (S = 0.0004×Gn*–0.0075, R2 = 0.834) and 95% confidence and prediction bands.
Mentions: The variations of swirling intensities obtained at all helical curvatures and pitches were analysed with the modified Germano number Gn* (figure 10). Regardless of Re, all S values are well overlapped and increase in proportion to Gn* (figure 10a). The linear regression line at 95% confidence and prediction bands (figure 10b) shows that S = 0.0004×Gn* − 0.0075 with R2 = 0.834. Helicity, an alternative parameter of S, also shows a linear increment with Gn*. The slopes of the helicity increment are dependent on Re (figure 11). The slopes of the linear regression are 2.15×10−7 (Re = 213, R2 = 0.859), 4.47×10−7 (Re = 410, R2 = 0.879), 5.22×10−7 (Re = 609, R2 = 0.896) and 9.82×10−7 (Re = 814, R2 = 0.838).

Bottom Line: Results showed that the swirling intensity and helicity of the swirling flow have a linear relation with a modified Germano number (Gn*) of the helical pipe.In addition, the swirling flow generated a beneficial flow structure at the stenosis by reducing the size of the recirculation flow under steady and pulsatile flow conditions.Therefore, the beneficial effects of a helical graft on the flow field can be estimated by using the magnitude of Gn*.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk, Republic of Korea.

ABSTRACT
Although a helical configuration of a prosthetic vascular graft appears to be clinically beneficial in suppressing thrombosis and intimal hyperplasia, an optimization of a helical design has yet to be achieved because of the lack of a detailed understanding on hemodynamic features in helical grafts and their fluid dynamic influences. In the present study, the swirling flow in a helical graft was hypothesized to have beneficial influences on a disturbed flow structure such as stenotic flow. The characteristics of swirling flows generated by helical tubes with various helical pitches and curvatures were investigated to prove the hypothesis. The fluid dynamic influences of these helical tubes on stenotic flow were quantitatively analysed by using a particle image velocimetry technique. Results showed that the swirling intensity and helicity of the swirling flow have a linear relation with a modified Germano number (Gn*) of the helical pipe. In addition, the swirling flow generated a beneficial flow structure at the stenosis by reducing the size of the recirculation flow under steady and pulsatile flow conditions. Therefore, the beneficial effects of a helical graft on the flow field can be estimated by using the magnitude of Gn*. Finally, an optimized helical design with a maximum Gn* was suggested for the future design of a vascular graft.

Show MeSH
Related in: MedlinePlus