Dynamics and wakes of freely settling and rising cubes

Ahmadi, Arman; Wachs, Anthony

doi:10.1103/physrevfluids.4.074304

Cited by 26 publications

(28 citation statements)

References 56 publications

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“…For cubic particles, for each value of

\overset{true‾}{ρ}

, the drag coefficient was found to increase significantly at

Re ≳ O (1 0^{2})

, consistent with the results shown in Figure 3a, before attaining an approximately constant value at higher Reynolds number. However, more pronounced increases in C D were reported for cubes with low

\overset{true‾}{ρ}

(Seyed‐Ahmadi and Wachs, 2019); at Re ≈ 200, the drag coefficient for

\overset{true‾}{ρ} = 0.2

was found to be approximately 20 % larger than when

\overset{true‾}{ρ} = 7

. A similar trend has previously been observed for thin circular discs (Jayaweera, 1965).…”

Section: Measurements Of CDsupporting

confidence: 76%

“…Also shown is the area ratio of the ice particle analogues. Further information on the identification of each analogue is available in Tables S1 to S4 of the supplementary material particles have reported that the relationship between Re and C D is sensitive to the density ratio ≡ p ∕ f for Re ≳ O(10 2 ) (Jenny et al, 2004;Veldhuis et al, 2009;Horowitz and Williamson, 2010;Ern et al, 2012;Seyed-Ahmadi and Wachs, 2019). In these studies, for a spherical particle, the drag coefficient was found to be independent of for > c .…”

Section: Measurements Of C Dmentioning

confidence: 95%

“…When falling unsteadily, the aerodynamics of falling particles could be sensitive to the relative densities of the particle

ρ_{p}

and the ambient fluid

ρ_{f}

in which it is falling. Studies of spherical and cubic particles have reported that the relationship between Re and C D is sensitive to the density ratio

\overset{true‾}{ρ} \equiv ρ_{p} / ρ_{f}

for

Re ≳ O (1 0^{2})

(Jenny et al ., 2004; Veldhuis et al ., 2009; Horowitz and Williamson, 2010; Ern et al ., 2012; Seyed‐Ahmadi and Wachs, 2019). In these studies, for a spherical particle, the drag coefficient was found to be independent of

\overset{true‾}{ρ}

for

\overset{true‾}{ρ} > {\overset{true‾}{ρ}}_{c}

.…”

Section: Measurements Of CDmentioning

confidence: 99%

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TRAIL part 2: A comprehensive assessment of ice particle fall speed parametrisations

McCorquodale

Westbrook

2020

Quart J Royal Meteoro Soc

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Results are presented from a comprehensive experimental campaign studying the aerodynamics of 3D-printed analogues of ice particles. Measurements of the drag coefficient of the analogues were acquired by using a novel experimental approach to digitally reconstruct the analogues' trajectory and orientation as they fall through a quiescent viscous liquid, using images acquired by a series of digital cameras. The data are used to evaluate commonly used parametrisations of ice particle fall speeds. We find that the accuracy of each of the parametrisations reduces at Reynolds numbers greater than approximately 100, as a result of effects associated with the onset of unsteady oscillating, fluttering or tumbling motions as the analogues fall. We propose a new fall speed parametrisation that predicts the measured drag coefficients at high Reynolds number with an accuracy consistent with that of the leading parametrisation at low Reynolds number.

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“…For cubic particles, for each value of

\overset{true‾}{ρ}

, the drag coefficient was found to increase significantly at

Re ≳ O (1 0^{2})

\overset{true‾}{ρ}

(Seyed‐Ahmadi and Wachs, 2019); at Re ≈ 200, the drag coefficient for

\overset{true‾}{ρ} = 0.2

was found to be approximately 20 % larger than when

\overset{true‾}{ρ} = 7

. A similar trend has previously been observed for thin circular discs (Jayaweera, 1965).…”

Section: Measurements Of CDsupporting

confidence: 76%

Section: Measurements Of C Dmentioning

confidence: 95%

“…When falling unsteadily, the aerodynamics of falling particles could be sensitive to the relative densities of the particle

ρ_{p}

and the ambient fluid

ρ_{f}

in which it is falling. Studies of spherical and cubic particles have reported that the relationship between Re and C D is sensitive to the density ratio

\overset{true‾}{ρ} \equiv ρ_{p} / ρ_{f}

for

Re ≳ O (1 0^{2})

\overset{true‾}{ρ}

for

\overset{true‾}{ρ} > {\overset{true‾}{ρ}}_{c}

.…”

Section: Measurements Of CDmentioning

confidence: 99%

See 1 more Smart Citation

TRAIL part 2: A comprehensive assessment of ice particle fall speed parametrisations

McCorquodale

Westbrook

2020

Quart J Royal Meteoro Soc

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“…In an extensive discussion of particle behavior in the Stokes and Newton regime, it was found that the density ratio ρ is also relevant, especially in the Newton regime. This is supported by various studies, suggesting that the trajectory might change depending on the density ratio [53][54][55]. A comparison showed their formula yielded the lowest deviation across all correlations discussed up to this point, and thereby is currently among the best-performing, together with the one proposed by Hölzer and Sommerfeld [23], to the knowledge of the authors.…”

Section: Drag Correlations For Non-spherical Particlessupporting

confidence: 62%

A Study on Shape-Dependent Settling of Single Particles with Equal Volume Using Surface Resolved Simulations

et al. 2021

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A detailed knowledge of the influence of a particle’s shape on its settling behavior is useful for the prediction and design of separation processes. Models in the available literature usually fit a given function to experimental data. In this work, a constructive and data-driven approach is presented to obtain new drag correlations. To date, the only considered shape parameters are derivatives of the axis lengths and the sphericity. This does not cover all relevant effects, since the process of settling for arbitrarily shaped particles is highly complex. This work extends the list of considered parameters by, e.g., convexity and roundness and evaluates the relevance of each. The aim is to find models describing the drag coefficient and settling velocity, based on this extended set of shape parameters. The data for the investigations are obtained by surface resolved simulations of superellipsoids, applying the homogenized lattice Boltzmann method. To closely study the influence of shape, the particles considered are equal in volume, and therefore cover a range of Reynolds numbers, limited to [9.64, 22.86]. Logistic and polynomial regressions are performed and the quality of the models is investigated with further statistical methods. In addition to the usually studied relation between drag coefficient and Reynolds number, the dependency of the terminal settling velocity on the shape parameters is also investigated. The found models are, with an adjusted coefficient of determination of 0.96 and 0.86, in good agreement with the data, yielding a mean deviation below 5.5% on the training and test dataset.

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“…Flows around cuboids are common in engineering applications in fact, for example, low speed positioning underwater vehicles, buoyancy blocks and free falling of non-spherical particles. The underwater vehicle and buoyancy block can be controlled and constrained by some means to keep steady in constant currents, and the free-falling and free-rising patterns of non-spherical particles can also be in a vertical path depending on the solid-to-fluid density ratio and Galileo number (Seyed-Ahmadi & Wachs 2019), all of which implies they can be represented by the ideal scenario of steady flow past a stationary cuboid. Therefore, a sound understanding of flow around the cube is important both fundamentally and practically.…”

Section: Introductionmentioning

confidence: 99%