Steady laminar flow in a 90° bend

Pantokratoras, Asterios

doi:10.1177/1687814016669472

Cited by 32 publications

(8 citation statements)

References 15 publications

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“…At the mid-diastolic time point, the region downstream of the inlet on the inner curvature exhibited higher WSS than on the outer curvature. This corroborated past experimental findings that at low Reynolds numbers, high WSS were typically found at the inner curvature of flow in curved channels [ 20 ], and findings in previous simulations of embryonic hearts [ 17 , 21 ]. The reason for this was that under the highly laminar and viscous flow environment, flow directions are easily bent by adverse pressure gradient in a curved channel, resulting in velocities being higher at the inner curvature than at the outer curvature and causing higher shear stresses at the inner curvature.…”

Section: Resultssupporting

confidence: 92%

Fluid mechanics of the zebrafish embryonic heart trabeculation

et al. 2022

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Embryonic heart development is a mechanosensitive process, where specific fluid forces are needed for the correct development, and abnormal mechanical stimuli can lead to malformations. It is thus important to understand the nature of embryonic heart fluid forces. However, the fluid dynamical behaviour close to the embryonic endocardial surface is very sensitive to the geometry and motion dynamics of fine-scale cardiac trabecular surface structures. Here, we conducted image-based computational fluid dynamics (CFD) simulations to quantify the fluid mechanics associated with the zebrafish embryonic heart trabeculae. To capture trabecular geometric and motion details, we used a fish line that expresses fluorescence at the endocardial cell membrane, and high resolution 3D confocal microscopy. Our endocardial wall shear stress (WSS) results were found to exceed those reported in existing literature, which were estimated using myocardial rather than endocardial boundaries. By conducting simulations of single intra-trabecular spaces under varied scenarios, where the translational or deformational motions (caused by contraction) were removed, we found that a squeeze flow effect was responsible for most of the WSS magnitude in the intra-trabecular spaces, rather than the shear interaction with the flow in the main ventricular chamber. We found that trabecular structures were responsible for the high spatial variability of the magnitude and oscillatory nature of WSS, and for reducing the endocardial deformational burden. We further found cells attached to the endocardium within the intra-trabecular spaces, which were likely embryonic hemogenic cells, whose presence increased endocardial WSS. Overall, our results suggested that a complex multi-component consideration of both anatomic features and motion dynamics were needed to quantify the trabeculated embryonic heart fluid mechanics.

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Section: Resultssupporting

confidence: 92%

Fluid mechanics of the zebrafish embryonic heart trabeculation

et al. 2022

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“…Monophasic flows in curved pipes are parametrized with the pipe-to-curvature radii ratio δ = r R (r being the pipe radius and R the radius of curvature of the pipe) and the Reynolds number Re = 2U x r ν (U x being the mean flow velocity and ν the viscosity) and the secondary flow is generally parametrized thanks to the Dean number D = Re δ. Even if numerous studies have been devoted to classify the secondary flow with the Dean number, the decay length (minimum length to recover an axisymmetric flow after the curved part) has received less attention and the results mainly concern a Ubend [30][31][32][33]. Thus, to assess the proposed geometry for the CoSmo breadboard, both numerical simulations with OpenFOAM and PIV measurements have been performed to ensure that the flow at the entrance of the test section remains axisymmetric for the mass fluxes of interest G ≤ 150 kg.m −2 .s −1 that corresponds to Reynolds numbers Re ≤ 2063.…”

Section: Single-phase Flow Qualificationmentioning

confidence: 99%

Conception of a compact flow boiling loop for the International Space Station- First results in parabolic flights

Chorin¹,

Boned²,

Sebilleau³

et al. 2023

Comptes Rendus. Mécanique

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The design of a pipe flow boiling experiment for the International Space Station is proposed, taking into account typical weight, power consumption and size constraints. The effect of singularities such as elbows upstream the test section is investigated. Velocity profiles downstream two elbows, measured by Particle Image Velocimetry are in good agreement with numerical simulation and allow to determine a specific distance (decay length) downstream the elbows for which the velocity profile recover its axisymmetry. From these results a breadboard is designed and tested in parabolic flights. Care has been taken to generate boiling downstream the decay length. Two-phase bubbly flow is observed with 2 perpendicular high-speed cameras in the test section and a symmetry of the bubble distribution in the pipe is verified for different gravity conditions when the bubbles are created after the decay length.

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“…Some of these studies include numerical simulations of the experiments using commercial fluid flow softwares such as ANSYS Fluent and OpenFOAM. A numerical assessment of the characteristics of laminar flow in a 90 • elbow was undertaken by van de Vosse et al [12] by adopting finite element methods and, more recently, by Pantokratoras [13] using ANSYS Fluent, who found that the velocity profiles at the bend inlet are shifted towards the inner pipe wall when the bend curvature is high, while they remain almost symmetric at low curvature. In addition, at high curvature and Reynolds numbers, the velocity profiles are shifted towards the outer pipe wall at the bend outlet and towards the inner wall at low Reynolds numbers, while when the curvature is low the velocity profiles are shifted towards the outer wall at the bend exit independently of the Reynolds number.…”

Section: Introductionmentioning

confidence: 99%

Smoothed Particle Hydrodynamics Simulations of Water Flow in a 90° Pipe Bend

Sigalotti

Alvarado-Rodríguez

Klapp

et al. 2021

Water

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The flow through pipe bends and elbows occurs in a wide range of applications. While many experimental data are available for such flows in the literature, their numerical simulation is less abundant. Here, we present highly-resolved simulations of laminar and turbulent water flow in a 90° pipe bend using Smoothed Particle Hydrodynamics (SPH) methods coupled to a Large-Eddy Simulation (LES) model for turbulence. Direct comparison with available experimental data is provided in terms of streamwise velocity profiles, turbulence intensity profiles and cross-sectional velocity maps at different stations upstream, inside and downstream of the pipe bend. The numerical results are in good agreement with the experimental data. In particular, maximum root-mean-square deviations from the experimental velocity profiles are always less than ∼1.4%. Convergence to the experimental measurements of the turbulent fluctuations is achieved by quadrupling the resolution necessary to guarantee convergence of the velocity profiles. At such resolution, the deviations from the experimental data are ∼0.8%. In addition, the cross-sectional velocity maps inside and downstream of the bend shows that the experimentally observed details of the secondary flow are also very well predicted by the numerical simulations.

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Steady laminar flow in a 90° bend

Cited by 32 publications

References 15 publications

Fluid mechanics of the zebrafish embryonic heart trabeculation

Fluid mechanics of the zebrafish embryonic heart trabeculation

Conception of a compact flow boiling loop for the International Space Station- First results in parabolic flights

Smoothed Particle Hydrodynamics Simulations of Water Flow in a 90° Pipe Bend

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