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Article

Modeling the Excess Velocity of Low-Viscous Taylor Droplets in Square Microchannels

1
Department of Environmental Process Engineering, University Bremen, Leobener Str. 6, 28359 Bremen, Germany
2
Department of Chemical Process Engineering, University Bremen, Leobener Str. 6, 28359 Bremen, Germany
*
Author to whom correspondence should be addressed.
Fluids 2019, 4(3), 162; https://doi.org/10.3390/fluids4030162
Received: 18 July 2019 / Revised: 22 August 2019 / Accepted: 26 August 2019 / Published: 2 September 2019
(This article belongs to the Special Issue Drop, Bubble and Particle Dynamics in Complex Fluids )
Microscopic multiphase flows have gained broad interest due to their capability to transfer processes into new operational windows and achieving significant process intensification. However, the hydrodynamic behavior of Taylor droplets is not yet entirely understood. In this work, we introduce a model to determine the excess velocity of Taylor droplets in square microchannels. This velocity difference between the droplet and the total superficial velocity of the flow has a direct influence on the droplet residence time and is linked to the pressure drop. Since the droplet does not occupy the entire channel cross-section, it enables the continuous phase to bypass the droplet through the corners. A consideration of the continuity equation generally relates the excess velocity to the mean flow velocity. We base the quantification of the bypass flow on a correlation for the droplet cap deformation from its static shape. The cap deformation reveals the forces of the flowing liquids exerted onto the interface and allows estimating the local driving pressure gradient for the bypass flow. The characterizing parameters are identified as the bypass length, the wall film thickness, the viscosity ratio between both phases and the C a number. The proposed model is adapted with a stochastic, metaheuristic optimization approach based on genetic algorithms. In addition, our model was successfully verified with high-speed camera measurements and published empirical data. View Full-Text
Keywords: Taylor flow; droplet excess velocity; droplet velocity model; microfluidics; genetic algorithms; greybox modeling Taylor flow; droplet excess velocity; droplet velocity model; microfluidics; genetic algorithms; greybox modeling
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MDPI and ACS Style

Helmers, T.; Kemper, P.; Thöming, J.; Mießner, U. Modeling the Excess Velocity of Low-Viscous Taylor Droplets in Square Microchannels. Fluids 2019, 4, 162. https://doi.org/10.3390/fluids4030162

AMA Style

Helmers T, Kemper P, Thöming J, Mießner U. Modeling the Excess Velocity of Low-Viscous Taylor Droplets in Square Microchannels. Fluids. 2019; 4(3):162. https://doi.org/10.3390/fluids4030162

Chicago/Turabian Style

Helmers, Thorben, Philip Kemper, Jorg Thöming, and Ulrich Mießner. 2019. "Modeling the Excess Velocity of Low-Viscous Taylor Droplets in Square Microchannels" Fluids 4, no. 3: 162. https://doi.org/10.3390/fluids4030162

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