Dean vortex stability using magnetic resonance flow imaging and numerical analysis

Mallubhotla, Hanuman; Belfort, Georges; Edelstein, William A.; Early, Thomas A.

doi:10.1002/aic.690470519

Cited by 25 publications

(9 citation statements)

References 49 publications

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“…The importance of this study lies in the hypotheses posed in literature concerning the relation between nature and persistence of secondary flow structures to cardiovascular diseases such as atherosclerosis and arterial aneurysms. [36][37][38][39][40][41][42][43] Moreover, if seeking to understand these flow structures developing in our arteries, it is crucial to know the effect of neglecting the non-Newtonian behavior of blood on these structures, especially when considering large arteries as it is common to assume blood to be Newtonian. Via the numerical simulations, the effects of the non-Newtonian viscosity on the flow structures are elucidated.…”

Section: Introductionmentioning

confidence: 99%

Non-Newtonian perspectives on pulsatile blood-analog flows in a 180° curved artery model

et al. 2015

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Complex, unsteady fluid flow phenomena in the arteries arise due to the pulsations of the heart that intermittently pumps the blood to the extremities of the body. The many different flow waveform variations observed throughout the arterial network are a result of this process and a function of the vessel properties. Large scale secondary flow structures are generated throughout the aortic arch and larger branches of the arteries. An experimental 180° curved artery test section with physiological inflow conditions was used to validate the computational methods implemented in this study. Good agreement of the secondary flow structures is obtained between experimental and numerical studies of a Newtonian blood-analog fluid under steady-state and pulsatile, carotid artery flow rate waveforms. Multiple vortical structures, some of opposite rotational sense to Dean vortices, similar to Lyne-type vortices, were observed to form during the systolic portion of the pulse. Computational tools were used to assess the effect of blood-analog fluid rheology (i.e., Newtonian versus non-Newtonian). It is demonstrated that non-Newtonian, blood-analog fluid rheology results in shear layer instabilities that alter the formation of vortical structures during the systolic deceleration and onwards during diastole. Additional vortices not observed in the Newtonian cases appear at the inside and outside of the bend at various times during the pulsation. The influence of blood-analog shear-thinning viscosity decreases mean pressure losses in contrast to the Newtonian blood analog fluid.

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Section: Introductionmentioning

confidence: 99%

Non-Newtonian perspectives on pulsatile blood-analog flows in a 180° curved artery model

et al. 2015

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“…The bifurcation of two-vortex (primary) solution into a four-vortex solution for ducts of circular cross-section appeared to occur at Dean number 960 (Daskopoulos and Lenhoff 1989). Effects of flow rate, geometry, and the ratio of the tube radius to that of curvature on the stability of Dean vortices were reported by Mallubhotla et al (2001). Twisting and bifurcation of vortices increased with increasing flow rate and radius ratio, and the observation of a six-vortex pattern was discussed Belfort et al, 2001).…”

Section: Steady Inflow Conditionsmentioning

confidence: 95%

“…A regime map to characterize Dean vortices was created for steady inflow conditions and Dean numbers up to 220, and later extended to 430 by Ligrani and Niver (1988) and Ligrani (1994). Transition of a two-vortex Dean-type system into a bifurcating four-vortex Dean-type system is described by Mallubhotla et al (2001) in another domain map. Development of secondary flows within a curved bend with unsteady forcing is expected to be driven by the rapid accelerations and decelerations inherent in such waveforms.…”

Section: Unsteady Inflow Conditionsmentioning

confidence: 99%

Secondary flow structures under stent-induced perturbations for cardiovascular flow in a curved artery model

Glenn

Bulusu

Shu

et al. 2012

International Journal of Heat and Fluid Flow

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“…8,10,12,13 However, industrial applications of such conduits ͑e.g., in membrane separation processes͒ typically involve two-phase mixtures of solid particles suspended in a liquid flow. So far, only limited attempts have been made to model gas-solid 14,15 and liquid-solid 16 flow systems for different applications.…”

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confidence: 99%

Three-dimensional fluid mechanics of particulate two-phase flows in U-bend and helical conduits

2006

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The results of numerous studies performed to date have shown that the performance of various hydraulic systems can be significantly improved by using curved conduit geometries instead of straight tubes. In particular, the formation of Dean vortices, which enhance the development of centrifugal instabilities, has been identified as a factor behind reducing the near-wall concentration buildup in particulate flow devices ͑e.g., in membrane filtration modules͒. Still, several issues regarding the effect of conduit curvature on local multidimensional phenomena governing fluid flow still remain open. A related issue is concerned with the impact that conduit geometry makes on the concentration distribution of a dispersed phase in two-phase flows in general, and in particulate flows ͑solid/liquid or solid/gas suspensions͒ in particular. It turns out that only very limited efforts have been made in the past to understand the fluid mechanics of such flows via advanced computer simulations. The purpose of this paper is to present the results of full three-dimensional ͑3D͒ theoretical and numerical analyses of single-and two-phase dilute particle/liquid flows in U-bend and helical curved conduits. The numerical analysis is based on computational fluid dynamics ͑CFD͒ simulations performed using a state-of-the-art multiphase flow computer code, NPHASE. The major issues discussed in the first part of the paper are concerned with the effect of curved/ coiled geometry on the evolution of flow field and the associated wall shear. It has been demonstrated that the primary curvature ͑a common factor for both the U-bend and helix geometries͒ may cause a substantial asymmetry in the radial distribution of the main flow velocity. This, in turn, leads to a significant, albeit highly nonuniform, increase in the wall shear stress. Specifically, the wall shear around the outer half of tube circumference may become twice the corresponding value for a straight tube, and gradually decrease to the straight tube level when approaching the inner bend location. Another important issue is concerned with the effect of the length of the curved section and of the straight tube just upstream of the bend. Specifically, the discontinuity in curvature at the straight-to-curved transition location results in a localized change in the wall shear distribution around the tube circumference. On the other hand, if the curved tube is sufficiently long, such as in the case of a helix, the asymmetric velocity profile eventually reaches a fully developed pattern. The effect of nondimensional flow parameters, the Reynolds and Dean numbers, on the entry length along the curved helix geometry is also investigated in this paper. It is shown that the predicted developing length agrees well with the existing experimental data. The objective of the second part of the paper is to investigate the mutual interactions between the liquid flow and solid particles in particulate two-phase flows in both the U-bend and helical geometries. It is shown that particle inertia causes ...

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Dean vortex stability using magnetic resonance flow imaging and numerical analysis

Abstract: Magnetic resonance flow imaging using flow encoding with spin warp imaging was used in three dimensions

Cited by 25 publications

References 49 publications

Non-Newtonian perspectives on pulsatile blood-analog flows in a 180° curved artery model

Non-Newtonian perspectives on pulsatile blood-analog flows in a 180° curved artery model

Secondary flow structures under stent-induced perturbations for cardiovascular flow in a curved artery model

Three-dimensional fluid mechanics of particulate two-phase flows in U-bend and helical conduits

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