A simple model for gas bubble drag reduction

Legner, Hartmut H.

doi:10.1063/1.864592

Cited by 76 publications

(39 citation statements)

References 4 publications

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“…Larger values of A lead to considerably large degrees of drag reduction. For A = 0.15, the result agrees reasonably with Legner's model which predicts %DR ≈ 1 − 5(1 − C) 2 /4 [11]. Note that according to Legner, there should be considerable drag enhancement when C = 0.…”

Section: B Drag Reduction With Flexible Bubblessupporting

confidence: 80%

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Drag reduction by compressible bubbles

L’vov

Procaccia

2006

Phys. Rev. E

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Drag reduction in stationary turbulent flows by bubbles is sensitive to the dynamics of bubble oscillations. Without this dynamical effect the bubbles only renormalize the fluid density and viscosity, an effect that by itself can only lead to a small percentage of drag reduction. We show in this paper that the dynamics of bubbles and their effect on the compressibility of the mixture can lead to a much higher drag reduction.

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Section: B Drag Reduction With Flexible Bubblessupporting

confidence: 80%

“…The aim of this paper is to study the drag reduction by bubbles when bubble oscillations are dominant. Finally we compare our finding with the results in Ref [11], showing that a nonphysical aspect of that theory is removed, while a good agreement with experiment is retained.…”

Section: Introductionsupporting

confidence: 56%

Drag reduction by compressible bubbles

L’vov

Procaccia

2006

Phys. Rev. E

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“…The decrease in the medium's density with increasing void fraction provides the primary mechanism for drag reduction with decreasing the bulk density of the medium in turbulence. 9 In contrast, the effective (bulk) viscosity of the fluid is estimated by Taylor …”

Section: Introductionmentioning

confidence: 99%

Intensified and attenuated waves in a microbubble Taylor–Couette flow

2013

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The effect of the presence of microbubbles on a flow state is experimentally investigated in a Taylor-Couette flow with azimuthal waves, in order to examine the interaction mechanism of bubbles and flows that result in drag reduction. The average diameter of the bubbles is 60 μm, which is smaller than the Kolmogorov length scale, and the maximum void fraction is 1.2 × 10 −4 at the maximum case. The modifications of the fluid properties, bulk density, effective viscosity, and the extra energy input caused by the addition of microbubbles are expected to have a small effect on modifying flow states. The power of the basic wave propagating in the azimuthal direction is enhanced; its modulation, however, is decreased by adding microbubbles in the flow regime corresponding to modulated Taylor vortex flow. Moreover, the gradient of the azimuthal velocity near the walls, source of the wall shear stress, decreases by 10%. The modified velocity distribution by adding microbubbles is comparable to that obtained with a 20% lower Reynolds number. Microbubbles in the coherent structure of the wavy Taylor vortices are visualized and exhibit a preferential distribution and motion at the crests and troughs of the waviness. The roles of the inhomogeneously distributed microbubbles in wavy vortical structures are discussed in view of our findings. C 2013 AIP Publishing LLC. [http://dx

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“…The drag reduction mechanism is not very well understood; only two rudimentary analytical/computational studies [9,10] have been attempted. While the key to a fundamental understanding of the phenomenon would appear to lie in an understanding of bubble dynamics in a boundary layer flow, it seems plausible from the computational work [9], when taken in concert with some bubble concentration profile measurements [4][5][6], that the bubbles provide a mechanism for increasing the kinematic viscosity near the buffer region, thereby destroving some of the turbulent production.…”

Section: Introductionmentioning

confidence: 99%

Microbubble skin friction reduction on an axisymmetric body

Deutsch

Castano

1986

The Physics of Fluids

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A reduction in skin friction drag is shown when gas is introduced into the liquid turbulent boundary layer of a submerged axisymmetric body. The 89 mm diameter, 632 mm long body has a cylindrical balance 273 mm long. Free stream speeds in the 305 mm diameter tunnel are as high as 17 m/sec, giving length Reynolds number of up to 10 million. In general, skin friction reduction is shown to increase with increasing free stream speed. At high speeds, helium injection is shown to be more effective at reducing skin friction than is air injection. Maximum skin friction reduction is near 80%—a value in good agreement with the maximum value observed in the flat plate work of Madavan et al. [Phys. Fluids 27, 356 (1984)]. While maximum skin friction reduction was found at a free stream speed of 5 m/sec for the flat plate geometry, maximum skin friction reduction was at a free stream speed of 17 m/sec for the axisymmetric geometry.

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A simple model for gas bubble drag reduction

Cited by 76 publications

References 4 publications

Drag reduction by compressible bubbles

Drag reduction by compressible bubbles

Intensified and attenuated waves in a microbubble Taylor–Couette flow

Microbubble skin friction reduction on an axisymmetric body

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