Effects of wall roughness on drag and lift forces of a particle at finite Reynolds number

Lee, Hyungoo; Balachandar, S.

doi:10.1016/j.ijmultiphaseflow.2016.09.006

Cited by 33 publications

(35 citation statements)

References 51 publications

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“…[] made direct measurements of lift and drag over a gravel bed, but also in low gradient streams with deep flow. They found for spherical particles that C D ∼ 0.76, C L was highly variable, and that peak deviations in drag and lift forces due to turbulence were large when particles protruded above the bed [see also Dwivedi et al ., ; Lee and Balachandar , ].…”

Section: Theoretical Considerationsmentioning

confidence: 99%

Direct measurements of lift and drag on shallowly submerged cobbles in steep streams: Implications for flow resistance and sediment transport

Lamb

Brun

Fuller

2017

Water Resources Research

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Steep mountain streams have higher resistance to flow and lower sediment transport rates than expected by comparison with low gradient rivers, and often these differences are attributed to reduced near‐bed flow velocities and stresses associated with form drag on channel forms and immobile boulders. However, few studies have directly measured drag and lift forces acting on bed sediment for shallow flows over coarse sediment, which ultimately control sediment transport rates and grain‐scale flow resistance. Here we report on particle lift and drag force measurements in flume experiments using a planar, fixed cobble bed over a wide range of channel slopes (0.004 < S < 0.3) and water discharges. Drag coefficients are similar to previous findings for submerged particles (CD ∼ 0.7) but increase significantly for partially submerged particles. In contrast, lift coefficients decrease from near unity to zero as the flow shallows and are strongly negative for partially submerged particles, indicating a downward force that pulls particles toward the bed. Fluctuating forces in lift and drag decrease with increasing relative roughness, and they scale with the depth‐averaged velocity squared rather than the bed shear stress. We find that, even in the absence of complex bed topography, shallow flows over coarse sediment are characterized by high flow resistance because of grain drag within a roughness layer that occupies a significant fraction of the total flow depth, and by heightened critical Shields numbers and reduced sediment fluxes because of reduced lift forces and reduced turbulent fluctuations.

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Section: Theoretical Considerationsmentioning

confidence: 99%

Direct measurements of lift and drag on shallowly submerged cobbles in steep streams: Implications for flow resistance and sediment transport

Lamb

Brun

Fuller

2017

Water Resources Research

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“…As in Jackson () and Hsu et al (), we consider separately the contributions of buoyancy and drag to the force between the liquid and granular phases and neglect other contributions. In numerical simulations, lift forces at high particle Reynolds numbers were found negligible for grains more than one particle radius away from the bed (Lee & Balanchandar, ). Likewise, the added mass force associated with mean relative acceleration between the grains and liquid (see, e.g., Geurst, ) can be neglected because the latter is 1 order of magnitude smaller than the convective acceleration of the mean flow.…”

Section: Two‐phase Momentum Balancementioning

confidence: 99%

Stresses and Drag in Turbulent Bed Load From Refractive Index‐Matched Experiments

Capart

2018

Geophysical Research Letters

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We report steady open‐channel flow experiments that resolve the internal dynamics of turbulent bed load layers at subgrain diameter resolution. Optical access is gained by using materials of matched refractive index, and a laser light sheet is scanned across the medium to capture both the solid and liquid motions over a 3‐D volume. The imaging measurements yield vertical profiles of granular concentration, solid and liquid mean velocity, and velocity fluctuation statistics including the granular temperature and the Reynolds stress. This makes it possible to determine all principal contributions to the momentum balance of each phase. In particular, experimental profiles are obtained for the stresses and interphase drag force. They are used to test constitutive relationships derived from kinetic theory, turbulence theory, and fluidization cell experiments.

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“…First, the incoming flow is not quiescent but turbulent: it is well known that a laminar wake in a turbulent background flow tends to recover somewhat faster than its counterpart in laminar flow (Amoura et al 2010; Zeng, Balachandar & Najjar 2010). Second, the sphere is not isolated, but it is located near a complex-shaped, evolving sediment bed: some researchers have indeed considered this problem (for a fixed single sphere), but the scaling of the wake length with Reynolds number was not explicitly obtained (Dey et al 2011; Lee & Balachandar 2017). In order to gauge the latter influence, we have performed a simulation with a single spanwise row of spheres placed adjacent to a macroscopically flat sediment bed holding all particles fixed.…”

Section: Discussionmentioning

confidence: 99%

On the scaling of the instability of a flat sediment bed with respect to ripple-like patterns

2020

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Effects of wall roughness on drag and lift forces of a particle at finite Reynolds number

Abstract: 2016-11-03T14:11:40

Cited by 33 publications

References 51 publications

Direct measurements of lift and drag on shallowly submerged cobbles in steep streams: Implications for flow resistance and sediment transport

Direct measurements of lift and drag on shallowly submerged cobbles in steep streams: Implications for flow resistance and sediment transport

Stresses and Drag in Turbulent Bed Load From Refractive Index‐Matched Experiments

On the scaling of the instability of a flat sediment bed with respect to ripple-like patterns

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