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TECHNICAL PAPERS

Bubble Effect on the Structures of Weakly Turbulent Couette Taylor Flow

[+] Author and Article Information
Amine Mehel, Celine Gabillet, Henda Djeridi

 Research Institute of French Naval Academy (IRENav), Ecole Navale BP 600, 29240 Brest Armee, France

J. Fluids Eng 128(4), 819-831 (May 25, 2005) (13 pages) doi:10.1115/1.2201641 History: Revised May 25, 2005; Received January 17, 2006

In industrial applications, rotating flows have been recognized to enhance mixing and transfer properties. Moreover, bubbly flows are also used to improve transfers. Therefore, it is interesting to study the effects of the dispersed phase on the structure of a Couette Taylor flow. Experiments are conducted for the quasi-periodic (Ta=780) and the weakly turbulent (Ta=1000) flow regimes. Bubbles (0.035 times as small as the gap) are generated by agitation of the upper free surface (ventilated flow). Larger bubbles (0.15 times as small as the gap) are generated by injection at the bottom of the apparatus and by applying a pressure drop (gaseous-cavitating flow). Void fraction, bubble size, and velocity, as well as axial and azimuthal velocity components of the liquid are investigated. The bubble location in the gap clearly depends on the bubble size. For α>0.1%, there is evidence of bubble-induced modifications of axial transfers and wall shear stress, the observed trends being different according to the bubble location in the gap.

Copyright © 2006 by American Society of Mechanical Engineers
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Figures

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Figure 1

General schematic of the apparatus

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Figure 2

Bubble size distribution for Ta=1000 in the vortices core (calculation is performed for 273 bubbles)

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Figure 3

Visualization of the bubble arrangement for ventilated flow: (a) Ωi=2.45rps(Ta=780), (b) Ωi=3.07rps(Ta=1000)

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Figure 4

Radial profiles of void fraction for ventilated flow: ◻:Ωi=2.45rps(Ta=780), ◇: Ωi=3.07rps(Ta=1000), x=r∕d−(Ri+R0)∕2d

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Figure 5

Visualization of the bubble arrangement for cavitating flow at Ta=1000: (a) nS=14, homogeneous, (b) nS=16, stratified, and (c) nS=16, homogeneous

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Figure 6

Evolution of the bubble strings number in cavitating flow: ◆: 3 strings, ∎: 8 strings, ▴: 14 strings, ×: 15 strings, *: 16 strings, ●: 17 strings

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Figure 7

Radial profiles of void fraction for cavitating flow in the 3rd bubble strings (Ta=780),x=r∕d−(Ri+R0)∕2d: ∎: core ns=15 stratified, ◻: outflow ns=15 stratified, ●: core ns=15 homogeneous, 엯: outflow ns=15 homogeneous

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Figure 8

Radial profiles of void fraction for cavitating flow in the third bubble stings (Ta=1000),x=r∕d−(Ri+R0)∕2d: ∎: core ns=16 stratified, ◻: outflow ns=16 stratified, ●: core ns=16 homogeneous, 엯: outflow ns=16 homogeneous

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Figure 9

Spectrum of the gas characteristic function obtained at Ta=780 for cavitating homogeneous flow (nS=15)

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Figure 10

Comparison between single phase flow and ventilated flow axial profiles of axial velocity for Ωi=3.07rps(Ta=1000):−−◆−−:single phase, −−◇−−: ventilated

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Figure 11

Radial profiles of azimuthal velocity in the outflow region of both the liquid phase and the bubbles for Ta=1000,x=r∕d−(Ri+R0)∕2d:◆: single phase, ◇: ventilated, ×: bubbles

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Figure 12

Axial profiles of axial velocity for Ta=1000. Comparison between single phase flow and homogeneous cavitating flow (nS=16):−−◆−−:single phase, −−◇−−:ns=16 homogeneous

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Figure 13

Radial profiles of azimuthal velocity of both the liquid phase and the bubbles for cavitating homogeneous flow at Ta=780(nS=15),x=r∕d−(Ri+Ro)∕2d: ∎: single phase outflow, ◻:ns=15 homogeneous, outflow, -: bubbles outflow, ●: single phase core, 엯: ns=15 homogeneous, core, +: bubbles core

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Figure 14

Radial profiles of azimuthal velocity of both the liquid phase and the bubbles for cavitating homogeneous flow at Ta=1000(nS=16),x=r∕d−(Ri+Ro)∕2d:◆: single phase outflow, ◇:ns=16 homogeneous outflow, ∎: bubbles outflow, ▴: single phase core, ▵:ns=16 homogeneous core, ×: bubbles core

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Figure 15

Comparison of the spectra obtained at Ta=780: dotted line, single phase flow; solid line, cavitating stratified flow (nS=15)

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Figure 16

Comparison of the spectra obtained at Ta=1000: dotted line, single phase flow; solid line, cavitating stratified flow (nS=16)

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