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TECHNICAL PAPERS

Experimental Study of Drop Deformation and Breakup in a Model Multitoothed Rotor-Stator

[+] Author and Article Information
David Megias-Alguacil1

ETH-Zürich, Laboratory of Food Process Engineering (LMVT), Schmelzbergstrasse 9, 8092 Zürich, Switzerlanddavid.megias@ilw.agrl.ethz.ch

Erich J. Windhab

ETH-Zürich, Laboratory of Food Process Engineering (LMVT), Schmelzbergstrasse 9, 8092 Zürich, Switzerland

1

Corresponding author.

J. Fluids Eng 128(6), 1289-1294 (May 02, 2006) (6 pages) doi:10.1115/1.2354528 History: Received October 20, 2005; Revised May 02, 2006

The objective of this work is to experimentally study the deformation behavior and breakup process suffered by a droplet submitted to the complex flow developed in a model multitoothed rotor-stator. The studied systems consist of an aqueous solution of polyvinylpyrrolidone in which droplets of diverse silicon oils are dispersed. Experiments are recorded with a digital camera, placed in vertical position, whose images are digitally analyzed. It is found that the drop deformation increases with increasing rotor rotational velocity, showing peaks of deformation corresponding to the proximity of the teeth. Drop breakup is achieved for all studied viscosity ratios. The breakup mechanism depends on the rotor-stator rotational dynamics, with breakup being more effective when the rotor teeth approach the stator teeth.

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Copyright © 2006 by American Society of Mechanical Engineers
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Figures

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Figure 1

Scheme of the multitoothed rotor-stator

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Figure 2

Shear, γ̇, and extensional, ε̇, rates along: (a) flow-line close to the stator wall for ω=0.11∕s and RS1 setup (λ=0.3); (b) flow-line in between the rotor and stator teeth for ω=0.11∕s and RS1 setup (λ=30) and (c) flow-line in between the rotor and stator teeth for ω=0.08s−1 and RS2 setup (λ=30)

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Figure 3

Drop deformation parameter D, as a function of time when the rotor moves clockwise (RS1). λ=0.1 and ω=0.41∕s. The drop insertion point was close to the stator wall. Solid line corresponds to a sinusoidal fitting.

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Figure 4

Drop deformation parameter D, as a function of time when the rotor moves clockwise (RS1). λ=0.3 and ω=0.11∕s. Drop insertion position close to the stator wall.

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Figure 5

Drop deformation parameter D, as a function of the product of the rotor angular velocity ω, and drop radius R, for the different viscosities ratios λ, when the rotor moves clockwise (RS1). Drop insertion position close to the stator wall.

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Figure 6

Drop deformation parameter D, as a function of time when the rotor moves clockwise (RS1). λ=30 and ω=0.21∕s. Drop insertion position in-between the rotor and stator teeth.

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Figure 7

Drop deformation parameter D, as a function of the product ωR, for the different viscosities ratios λ, when the rotor moves clockwise (RS1). Drop insertion position in-between the rotor and stator teeth.

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Figure 8

Drop deformation parameter D, as a function of time when the rotor moves counterclockwise (RS2). λ=30 and ω=0.081∕s.

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Figure 9

Drop deformation parameter D, as a function of the rotor product ωR, for the different viscosities ratios λ, when the rotor moves counterclockwise (RS2)

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Figure 10

Photographs of the drop breakup for the viscosity ratios: (a)λ=0.3, (b)λ=3.3, and (c)λ=30.0

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Figure 11

Critical rotor speed (multiplied by the drop radius) and deformation for drop breakup as a function of λ. Lines for Dcrit correspond to Eq. 3 (solid line) and Eq. (4) (dashed line).

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