Simulations of Flow in Curved Tubes

Guan, Xu; Martonen, T. B.

doi:10.1080/02786829708965448

Cited by 25 publications

(13 citation statements)

References 14 publications

(22 reference statements)

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“…Unfortunately, their results are affected by heavy irregularities and are of little use for benchmarking purposes. However, Guan and Martonen [24] conducted CFD simulations of the above experiments using the finite element code FIDAP, and reported a fair overall agreement with the results in Ref. [23].…”

Section: Entry Effects and Single Bendssupporting

confidence: 50%

Fully developed laminar flow and heat transfer in serpentine pipes

Ciofalo

Liberto

2015

International Journal of Thermal Sciences

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Section: Entry Effects and Single Bendssupporting

confidence: 50%

Fully developed laminar flow and heat transfer in serpentine pipes

Ciofalo

Liberto

2015

International Journal of Thermal Sciences

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“…Yao and Berger (1975) compared the values of the developing length of a toric geometry (L DT ) to a straight one (L DS ), for which the relevant formula is , commonly used ratio: (1983) filled this work out by stating that equations provided by Yao and Berger (1975) satisfies the following relation, under the hypotheses of an uncompressible, steady and laminar flow in a circular and rigid pipe, with a uniform curvature: (9) In this inequality, the lower bound stands for the developing length inside a straight tube, and the upper bound the validity range of the Singh and Bell (1974) solution. Martonen (1997 &2000) studied the development of a flow in a torus. Their work is about the transitory feature of the flow for Dean number values between 10 and 250, with the use of the commercial hydrodynamic modelling software FIDAP.…”

Section: Introductionmentioning

confidence: 99%

Developing Lengths in Woven and Helical Tubes with Dean Vortices Flows

Springer

Carretier

Veyret

et al. 2009

Engineering Applications of Computational Fluid Mechanics

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Coiling membranes help to create in a flow Dean vortices which enhance flux permeation and bring improvement to membrane filtration processes. The Dean number enables prediction of the appearance of those vortices. As it increases, a secondary flow appears with one pair of vortices. However, this flow profile needs a certain length to be fully developed. For membrane processes, it is useful to know this developing length so one can calculate the exact membrane area under such Dean shear stress. Developing angles or lengths were already simulated for a parabolic and a uniform inlet flow for a torus. In this study, we determined numerically the developing length for different kinds of tori and for woven or helical tubes. The simulations featured parameters of wide ranges of validity: internal diameter (0.25-1 mm), coil diameter (4-32 mm), Reynolds number (0-400) and pitch (2-32 mm) for the helical shape.

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“…These shear stresses (and shear rates) are easily high enough to support platelet-mediated thrombus formation. We previously demonstrated that increases in wall shear stress encountered when flow traverses a prominent bend or curve in a vessel (or conduit), as shown in red in Figure 6 and orange in Figure 7, arise as a consequence of reactive centrifugal effects creating patterns of recirculating flow in the crosssectional plane of the tube [29,[42][43][44]. This fluid motion can organize into spiral flow fields that, in their rotational motion, augment local shearing without hemorrhagic complications.…”

Section: Discussionmentioning

confidence: 99%

Catheter-Directed Thrombolysis for Occluded Central (Ascending Aorta-to-Pulmonary Artery) Shunts: Importance of Shear Stress-Induced, Platelet-Mediated Thrombosis

Singh¹,

Sernich²,

Siwik³

et al. 2016

jshd

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A central (ascending aorta-to-pulmonary artery) shunt is a standard palliative operation for infants with cyanotic congenital heart disease. Thrombosis of these shunts can be life-threatening. We report our experience with catheter-directed thrombolysis using recombinant tissue plasminogen activator to locally treat totally occluded central shunts as an alternative to surgery. Ten patients (median age 47 days) successfully underwent the procedure. Following thrombolysis, shunt patency was verified by angiography. The arterial oxygen (O 2 ) saturations in 100% O 2 increased from a median value of 55% to 90%. Major bleeding did not occur in any patients. Computational fluid dynamics was used to identify a relationship between shunt hemodynamics and thrombosis. We retrospectively analyzed blood flow through simulations of these shunts as they would have appeared prior to obstruction. The calculations revealed that flow negotiating "angulated" portions of these central shunts produced wall shear stresses of 157-168 Pa (or N/m 2 ), with shear rates reaching 31,400-33,600/s. These values are easily high enough to initiate platelet activation/aggregation, leading to thrombus formation. We conclude that: 1) catheter-directed thrombolysis can be used to rapidly, effectively, and safely resolve total central shunt occlusion in critically ill neonates and 2) central shunts containing prominent angulation are at risk for developing shear stress-induced, plateletmediated thrombosis. This finding is clinically important as this flow-directed process is not affected by prophylactic aspirin against shunt thrombosis.

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Simulations of Flow in Curved Tubes

Cited by 25 publications

References 14 publications

Fully developed laminar flow and heat transfer in serpentine pipes

Fully developed laminar flow and heat transfer in serpentine pipes

Developing Lengths in Woven and Helical Tubes with Dean Vortices Flows

Catheter-Directed Thrombolysis for Occluded Central (Ascending Aorta-to-Pulmonary Artery) Shunts: Importance of Shear Stress-Induced, Platelet-Mediated Thrombosis

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