Wall effect for spheres falling at small reynolds number in a viscoplastic medium

Atapattu, D.D.; Chhabra, R.P.; Uhlherr, P. H. T.

doi:10.1016/0377-0257(90)85031-s

Cited by 79 publications

(53 citation statements)

References 16 publications

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“…This complex behavior clearly indicates that the walls have a significant effect on the bubble motion for R/R c 0.5. This is to be expected from previous studies of the motion of solid spheres through yield-stress fluids [30,31]. No such peak or plateau regime was observed in the present work, in which R eff /R c is always less than 0.28 and wall effects are much less significant.…”

Section: Discussionsupporting

confidence: 86%

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Motion and shape of bubbles rising through a yield-stress fluid

Sikorski

Tabuteau

Bruyn

2009

Journal of Non-Newtonian Fluid Mechanics

109

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a b s t r a c tWe study the velocity and shape of air bubbles rising through a transparent yield-stress fluid. The bubbles are small enough compared to the experimental vessel that effects of walls are weak. We find that the terminal rise velocity of the bubbles increases approximately linearly with bubble radius over the range of volumes accessible in our experiments. We observe bubble motion only when the bubbles are larger than a certain critical radius. In terms of a dimensionless yield parameter Y, the ratio between the force due to the yield stress and the buoyant force, we observe bubble motion only for Y 0.50 ± 0.04. The bubbles are non-spherical, having the shape of an inverted teardrop with a rounded head and a cusp-like tail. The cusps may be an indication that elasticity plays a significant role in this system. By fitting the cross-sectional radius of the bubble as a function of the axial coordinate to an empirical function, we study the dependence of the bubble shape on volume and the yield stress of the material.

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Section: Discussionsupporting

confidence: 86%

“…For our experiments, R eff /R c ≤ 0.28. For these values of the size ratio, wall effects would be expected to contribute at most about 15% to the drag on a sphere moving through a yield-stress fluid [30]. The effect of walls on bubble motion has not previously been measured but is likely to be of a similar magnitude.…”

Section: Experiments and Materialsmentioning

confidence: 89%

Motion and shape of bubbles rising through a yield-stress fluid

Sikorski

Tabuteau

Bruyn

2009

Journal of Non-Newtonian Fluid Mechanics

109

View full text Add to dashboard Cite

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“…The dimensions of the column (0.2 m Â 0.2 m Â 1.2 m) have been selected based on the rheology of the test solutions, such that particles having diameter of less than 10 mm can fall through the fluids without experiencing significant wall effects (Atapattu et al, 1990). The walls of the column were made of clear Perspex.…”

Section: Experimental Methodsmentioning

confidence: 99%

A new fluid model for particles settling in a viscoplastic fluid

Gumulya

Horsley

Wilson

et al. 2011

Chemical Engineering Science

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“…Typically, the ratio between reservoir diameter and characteristic size of the object is of the order of 5. Given the yield stresses and velocities involved, the objects may be Ž considered to be in an infinite medium Atapattu et al, 1990Atapattu et al, , 1995Beaulne and Mitsoulis, 1997;Blackery and Mitsoulis, . 1997 .…”

Section: Methodsmentioning

confidence: 99%

Drag and stability of objects in a yield stress fluid

2001

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The drag force exerted on objects in a yield stress fluid was measured when the ®elocities become infinitely slow. In these quasi-static conditions, yield stress effects are predominant. Particular care was paid to determining the yield stress and checking interface conditions when characterizing these fluids from a rheometric standpoint. Drag coefficients could then be determined for interesting objects of ®arious shapes. The important role of fluid-object interface effects was also highlighted. On the basis of these results, a stability criterion is proposed for the object in the fluid, to estimate the yield stress needed to balance buoyancy forces.

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Wall effect for spheres falling at small reynolds number in a viscoplastic medium

Cited by 79 publications

References 16 publications

Motion and shape of bubbles rising through a yield-stress fluid

Motion and shape of bubbles rising through a yield-stress fluid

A new fluid model for particles settling in a viscoplastic fluid

Drag and stability of objects in a yield stress fluid

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