Suspensions of finite-size neutrally buoyant spheres in turbulent duct flow

Fornari, Walter; Kazerooni, Hamid Tabaei; Hussong, Jeanette; Brandt, Luca

doi:10.1017/jfm.2018.490

Cited by 25 publications

(20 citation statements)

References 70 publications

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“…For φ = 5 and 10%, compared to the single phase NF case, the streamwise velocity fluctuations marginally increase above the wall-normal location y/H ≈ 0.2 while they decrease below y/H ≈ 0.2. Such a behaviour was also observed, albeit more pronounced, in [18] at φ = 5 and 10%. With further increase in φ, the streamwise velocity fluctuations reduce for all wall-normal locations in our study.…”

Section: Velocity Statisticssupporting

confidence: 58%

Turbulence modulation by finite-size spherical particles in Newtonian and viscoelastic fluids

Zade

Lundell

Brandt

2019

International Journal of Multiphase Flow

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We experimentally investigate the influence of finite-size spherical particles in turbulent flows of a Newtonian and a drag reducing viscoelastic fluid at varying particle volume fractions and fixed Reynolds number. Experiments are performed in a square duct at a Reynolds number Re 2H of nearly 1.1 × 10 4 , Weissenberg number W i for single phase flow is between 1-2 and results in a * Corresponding author

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Section: Velocity Statisticssupporting

confidence: 58%

Turbulence modulation by finite-size spherical particles in Newtonian and viscoelastic fluids

Zade

Lundell

Brandt

2019

International Journal of Multiphase Flow

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“…The simulations confirm the largest concentration at the core of the duct at φ = 20% and that the Reynolds stresses are typically lower than those of the single phase flow, as also generally found in this study. Fornari et al (2018a) suggest that turbulence is largely attenuated at this φ: turbulence production is reduced, but this is compensated by a large increase in energy injection due to particle-induce stresses.…”

Section: Discussionmentioning

confidence: 94%

“…To explain the cause for the non-monotonic pressure drop at the highest volume fraction φ = 20% and higher Re 2H (where the influence of gravity on pressure drop is negligible) we consider the variation of concentration and mean-streamwise velocity profile in the plane of the wall bisector, as sketched in figure 20. Velocity and concentration measurements have been performed for LP and MP only whereas a qualitative picture is proposed for SP based on the pressure drop measurements and the simulations in Fornari et al (2018a) for neutrally buoyant particles as their size in inner units (20δ ν ) is in range of our experiments for SP (15-37δ ν ). The simulations are, however, performed at a lower Re 2H = 5600 and the particle size in bulk units is 2H/d p = 18, similar to MP in experiments.…”

Section: Discussionmentioning

confidence: 99%

“…However, the particles studied here are larger than those in Costa et al (2016) and a square duct has 2 inhomogeneous directions and the two additional walls on the sides prevent the particle lateral motion. This confinement leads to a peak in the particle concentration profile at the duct core at high φ, as shown in Fornari et al (2018a). The presence of weak secondary flow in the square duct would also influence the momentum balance, thus causing further deviations from a channel flow, where no secondary motion is seen.…”

Section: High Volume Fraction (φ = 20%)mentioning

confidence: 91%

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Experimental investigation of turbulent suspensions of spherical particles in a square duct

et al. 2018

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We report experimental observations of turbulent flow with spherical particles in a square duct. Three particle sizes namely: 2H/d p = 40, 16 and 9 (2H being the duct full height and d p being the particle diameter) are investigated. The particles are nearly neutrallybuoyant with a density ratio of 1.0035 and 1.01 with respect to the suspending fluid. Refractive Index Matched -Particle Image Velocimetry (RIM-PIV) is used for fluid velocity measurement even at the highest particle volume fraction (20%) and Particle Tracking Velocimetry (PTV) for the particle velocity statistics for the flows seeded with particles of the two largest sizes, whereas only pressure measurements are reported for the smallest particles. Settling effects are seen at the lowest bulk Reynolds number Re 2H ≈ 10000 whereas, at the highest Re 2H ≈ 27000, particles are in almost full suspension. The friction factor of the suspensions is found to be significantly larger than that of singlephase duct flow at the lower Re 2H investigated; however, the difference decreases when increasing the flow rate and the total drag approaches the values of the single phase flow at the higher Reynolds number considered, Re 2H = 27000. The pressure drop is found to decrease with the particle diameter for volume fractions lower than φ = 10% for nearly all Re 2H investigated. However, at the highest volume fraction φ = 20%, we report a peculiar non-monotonic behavior: the pressure drop first decreases and then increases with increasing particle size. The decrease of the turbulent drag with particle size at the lowest volume fractions is related to an attenuation of the turbulence. The drag increase for the two largest particle sizes at φ = 20%, however, occurs despite this large reduction of the turbulent stresses, and it is therefore due to significant particle-induced stresses. At the lowest Reynolds number, the particles reside mostly in the bottom half of the duct where the mean velocity significantly decreases; the flow is similar to that in a moving porous bed near the bottom wall and to turbulent duct flow with low particle concentration near the top wall. † Email address for correspondence: luca@mech.kth.se arXiv:1809.06607v1 [physics.flu-dyn]

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“…Also, at constant Φ and pressure gradient, the flow rate reduced as the particle settling effect increased (lower Sh). It is also worth to note the recent simulations of [8] for neutrally buoyant particles in a square duct up to a volume fraction of 20%. These authors found that for Φ ≤ 10%, particles preferentially accumulate on the corner bisectors and turbulence production is enhanced, whereas at Φ = 20% particles migrate towards the core region and turbulence production decreases below the values for Φ = 5%.…”

Section: Introductionmentioning

confidence: 97%

Buoyant finite-size particles in turbulent duct flow

et al. 2019

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Particle Image Velocimetry (PIV) and Particle Tracking Velocimetry (PTV) have been employed to investigate the dynamics of finite-size spherical particles, slightly heavier than the carrier fluid, in a horizontal turbulent square duct flow. Interface resolved Direct Numerical Simulations (DNS) have also been performed with the Immersed Boundary Method (IBM) at the same experimental conditions, bulk Reynolds number Re 2H = 5600, duct height to particle size ratio 2H/d p = 14.5, particle volume fraction Φ = 1% and particle to fluid density ratio ρ p /ρ f = 1.0035. A good agreement has been observed between experiments and simulations in terms of the overall pressure drop, concentration distribution and turbulent statistics of the two phases. Additional experimental results considering two particle sizes, 2H/d p = 14.5 and 9 and multiple Φ = 1, 2, 3, 4 and 5% are reported at the same Re 2H . The pressure drop monotonically increases with the volume fraction, almost linearly and nearly independently of the particle size for the above parameters. However, despite the similar pressure drop, the microscopic picture, the fluid velocity statistics, differs significantly with the particle size. This one-to-one comparison between simulations and experiments extends the validity of interface resolved DNS in complex turbulent multiphase flows and highlights the ability of experiments to investigate such flows in considerable details, even in regions where the local volume fraction is relatively high. *

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Suspensions of finite-size neutrally buoyant spheres in turbulent duct flow

Cited by 25 publications

References 70 publications

Turbulence modulation by finite-size spherical particles in Newtonian and viscoelastic fluids

Turbulence modulation by finite-size spherical particles in Newtonian and viscoelastic fluids

Experimental investigation of turbulent suspensions of spherical particles in a square duct

Buoyant finite-size particles in turbulent duct flow

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