Dynamics of isolated confined air bubbles in liquid flows through circular microchannels: an experimental and numerical study

Khodaparast, Sepideh; Magnini, Mirco; Borhani, Navid; Thome, John R.

doi:10.1007/s10404-015-1566-4

Cited by 44 publications

(71 citation statements)

References 66 publications

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“…Simulations were conducted using meshes of different levels of refinement, and the results shown in Figure are grid independent. Good agreement is observed in Figure between the present simulations and those of Khodaparast et al as well as between simulations and the experiment. The bubble velocity at steady state was also compared to the experimental one.…”

Section: Numerical Resultssupporting

confidence: 90%

“…Figure 11 shows a schematic of the initial bubble shape and the boundary conditions. The bubble's initial volume is the region enclosed by a cylinder of radius a and 35 the radius a was fixed and b was calculated such that the volume was equal to the volume of the experimental bubble. The density and viscosity ratios for the first case are 3.4510 −5 and 9.610 −4 , respectively, and the nondimensional numbers are given by Re = 0.01286, We = 0.001278.…”

Section: Axisymmetric Slug Flow In a Microchannelmentioning

confidence: 99%

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Interface‐fitted moving mesh method for axisymmetric two‐phase flow in microchannels

Gros

Anjos

Thome

2017

Numerical Methods in Fluids

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Summary A boundary‐fitted moving mesh scheme is presented for the simulation of two‐phase flow in two‐dimensional and axisymmetric geometries. The incompressible Navier‐Stokes equations are solved using the finite element method, and the mini element is used to satisfy the inf‐sup condition. The interface between the phases is represented explicitly by an interface adapted mesh, thus allowing a sharp transition of the fluid properties. Surface tension is modelled as a volume force and is discretized in a consistent manner, thus allowing to obtain exact equilibrium (up to rounding errors) with the pressure gradient. This is demonstrated for a spherical droplet moving in a constant flow field. The curvature of the interface, required for the surface tension term, is efficiently computed with simple but very accurate geometric formulas. An adaptive moving mesh technique, where smoothing mesh velocities and remeshing are used to preserve the mesh quality, is developed and presented. Mesh refinement strategies, allowing tailoring of the refinement of the computational mesh, are also discussed. Accuracy and robustness of the present method are demonstrated on several validation test cases. The method is developed with the prospect of being applied to microfluidic flows and the simulation of microchannel evaporators used for electronics cooling. Therefore, the simulation results for the flow of a bubble in a microchannel are presented and compared to experimental data.

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Section: Numerical Resultssupporting

confidence: 90%

Section: Axisymmetric Slug Flow In a Microchannelmentioning

confidence: 99%

Interface‐fitted moving mesh method for axisymmetric two‐phase flow in microchannels

Gros

Anjos

Thome

2017

Numerical Methods in Fluids

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“…With the use of Eqs. (32) and (68), the velocity u ∞ can be expressed as a function of H ∞ /R. The critical uniform film thickness for the appearance of recirculation regions, H ∞ , is obtained by solving u ∞ (0) = 0, resulting in Eqs.…”

Section: Derivation Of the Critical Uniform Film Thickness For The mentioning

confidence: 99%

“…Reduced liquid quantities are commonly used as individual reactors in several biological and chemical applications [34], as well as in industrial processes [1] and in micro-scale heat and mass transfer equipments [40,58,44]. Bubbles and droplets often flow in microchannels with a round or rectangular/square crosssection [35,32,44].…”

mentioning

confidence: 99%

Viscous Taylor droplets in axisymmetric and planar tubes: from Bretherton’s theory to empirical models

Balestra

Zhu

Gallaire

2018

Microfluid Nanofluid

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The aim of this study is to derive accurate models for quantities characterizing the dynamics of droplets of non-vanishing viscosity in capillaries. In particular, we propose models for the uniform-film thickness separating the droplet from the tube walls, for the droplet front and rear curvatures and pressure jumps, and for the droplet velocity in a range of capillary numbers, Ca, from 10 −4 to 1 and inner-to-outer viscosity ratios, λ , from 0, i.e. a bubble, to high viscosity droplets. Theoretical asymptotic results obtained in the limit of small capillary number are combined with accurate numerical simulations at larger Ca. With these models at hand, we can compute the pressure drop induced by the droplet. The film thickness at low capillary numbers (Ca < 10 −3 ) agrees well with Bretherton's scaling for bubbles as long as λ < 1. For larger viscosity ratios, the film thickness increases monotonically, before saturating for λ > 10 3 to a value 2 2/3 times larger than the film thickness of a bubble. At larger capillary numbers, the film thickness follows the rational function proposed by Aussillous & Quéré [5] for bubbles, with a fitting coefficient which

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“…CFD is a useful computing tool that uses numerical analysis to solve and investigate problems that involve fluid flows [24][25][26]. It simulates the interaction of liquids and gases with surfaces defined by boundary conditions [27]. This method has already been used to simulate photo-electrochemical reactors for hydrogen production [28], and other types of fuel cells, such as solid oxide [29] or redox cells [30].…”

Section: Introductionmentioning

confidence: 99%

Hydrodynamics and Oxygen Bubble Characterization of Catalytic Cells Used in Artificial Photosynthesis by Means of CFD

Torras

Lorente

Hernández

et al. 2017

Fluids

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Miniaturized cells can be used in photo-electrochemistry to perform water splitting. The geometry, process variables and removal of oxygen bubbles in these cells need to be optimized. Bubbles tend to remain attached to the catalytic surface, thus blocking the reaction, and they therefore need to be dragged out of the cell. Computational Fluid Dynamics simulations have been carried out to assess the design of miniaturized cells and their results have been compared with experimental results. It has been found that low liquid inlet velocities (~0.1 m/s) favor the homogeneous distribution of the flow. Moderate velocities (0.5-1 m/s) favor preferred paths. High velocities (~2 m/s) lead to turbulent behavior of the flow, but avoid bubble coalescence and help to drag the bubbles. Gravity has a limited effect at this velocity. Finally, channeled cells have also been analyzed and they allow a good flow distribution, but part of the catalytic area could be lost. The here presented results can be used as guidelines for the optimum design of photocatalytic cells for the water splitting reaction for the production of solar fuels, such as H 2 or other CO 2 reduction products (i.e., CO, CH 4 , among others).

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Dynamics of isolated confined air bubbles in liquid flows through circular microchannels: an experimental and numerical study

Cited by 44 publications

References 66 publications

Interface‐fitted moving mesh method for axisymmetric two‐phase flow in microchannels

Interface‐fitted moving mesh method for axisymmetric two‐phase flow in microchannels

Viscous Taylor droplets in axisymmetric and planar tubes: from Bretherton’s theory to empirical models

Hydrodynamics and Oxygen Bubble Characterization of Catalytic Cells Used in Artificial Photosynthesis by Means of CFD

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