Simulation of micro-flow dynamics at low capillary numbers using adaptive interface compression

Aboukhedr, Mahmoud; Georgoulas, Anastasios; Marengo, Marco; Gavaises, Manolis; Vogiatzaki, Konstantina

doi:10.1016/j.compfluid.2018.01.009

Cited by 25 publications

(19 citation statements)

References 48 publications

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“…The FSF model has been reported to provide periodic bursts in the velocity fields but lower spurious current than SSF [42]. The approach has been used to model bubbles in microfluidic devices [51] and flow through porous media [52]. Denner et al [77] Proposed the use of artificial viscosity model, which applies artificial shear stress in the tangential direction to interface, to dampen the spurious currents.…”

Section: Publication Remarksmentioning

confidence: 99%

“…In the literature, C α can be set between 0 and 4, where C α equal to zero and one correspond to the case of no and moderate compression, respectively [56]. The increase in the value of C α sharpens the interface but increases the magnitude of spurious currents (see [51,56]). To model practical flow scenarios using interFoam, the value of C α is generally set to unity [32,63].…”

Section: Governing Equationsmentioning

confidence: 99%

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Comparison of Surface Tension Models for the Volume of Fluid Method

Vachaparambil

Einarsrud

2019

Processes

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With the increasing use of Computational Fluid Dynamics to investigate multiphase flow scenarios, modelling surface tension effects has been a topic of active research. A well known associated problem is the generation of spurious velocities (or currents), arising due to inaccuracies in calculations of the surface tension force. These spurious currents cause nonphysical flows which can adversely affect the predictive capability of these simulations. In this paper, we implement the Continuum Surface Force (CSF), Smoothed CSF and Sharp Surface Force (SSF) models in OpenFOAM. The models were validated for various multiphase flow scenarios for Capillary numbers of 10 − 3 –10. All the surface tension models provide reasonable agreement with benchmarking data for rising bubble simulations. Both CSF and SSF models successfully predicted the capillary rise between two parallel plates, but Smoothed CSF could not provide reliable results. The evolution of spurious current were studied for millimetre-sized stationary bubbles. The results shows that SSF and CSF models generate the least and most spurious currents, respectively. We also show that maximum time step, mesh resolution and the under-relaxation factor used in the simulations affect the magnitude of spurious currents.

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Section: Publication Remarksmentioning

confidence: 99%

Section: Governing Equationsmentioning

confidence: 99%

Comparison of Surface Tension Models for the Volume of Fluid Method

Vachaparambil

Einarsrud

2019

Processes

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“…Great effort has been dedicated to correctly account for the transport of the interface and the consideration of the capillary forces. The role of the capillary forces is important both in cases with low velocity impact where capillary forces dominate throughout the process as well as to high impact case where although in the initial stages of the impact inertia is dominant as the droplets spread and slow down, capillarity becomes significant [7][8][9].…”

Section: Introductionmentioning

confidence: 99%

Numerical Treatment of the Interface in Two Phase Flows Using a Compressible Framework in OpenFOAM: Demonstration on a High Velocity Droplet Impact Case

Tretola

Vogiatzaki

2021

Fluids

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The ability to accurately predict the dynamics of fast moving and deforming interfaces is of interest to a number of applications including ink printing, drug delivery and fuel injection. In the current work we present a new compressible framework within OpenFOAM which incorporates mitigation strategies for the well known issue of spurious currents. The framework incorporates the compressible algebraic Volume-of-Fluid (VoF) method with additional interfacial treatment techniques including volume fraction smoothing and sharpening (for the calculation of the interface geometries and surface tension force, respectively) as well as filtering of the capillary forces. The framework is tested against different benchmarks: A 2D stationary droplet, a high velocity impact droplet case (500 m/s impact velocity) against a dry substrate and, with the same impact conditions, against a liquid film. For the 2D static droplet case, our results are consistent with what is observed in the literature when these strategies are implemented within incompressible frameworks. For the high impact droplet cases we find that accounting for both compressibility and correct representation of the interface is very important in numerical simulations, since pressure waves develop and propagate within the droplet interacting with the interface. While the implemented strategies do not alter the dynamics of the impact and the droplet shape, they have a considerable effect on the lamella formation. Our numerical method, although currently implemented for droplet cases, can also be used for any fast moving interface with or without considering the impact on a surface.

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“…Most literature studies on SC consider simplified conditions with similar or equal phase densities and viscosities [49,51,52,56,57,63,65,[69][70][71][72][73][74], entirely nondimensional test cases [75], artificially large drops [50,76,77] or combinations of these restrictions. There are only very few studies, where the practically most relevant air water-system is considered for a droplet [78] or a bubble [64].…”

mentioning

confidence: 99%

“…No special measures haven been undertaken to reduce spurious currents. For techniques to reduce SC in IF, the interested reader is referred to[55,74,[82][83][84][85].…”

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confidence: 99%

On suitability of phase-field and algebraic volume-of-fluid OpenFOAM® solvers for gas–liquid microfluidic applications

Jamshidi

Heimel

Hasert

et al. 2019

Computer Physics Communications

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Microfluidic devices often contain several phases. Their design can be supported by interface-resolving numerical simulations, requiring accurate methods and validated computer codes. Especially challenging are submillimetre air bubbles in water due to their large density contrast and dominance of surface tension. Here, we evaluate two numerical methods implemented in OpenFOAM ® , namely the standard solver interFoam with an algebraic volume-of-fluid method relying on a sharp interface representation and phaseFieldFoam relying on the phase-field method with diffuse interface representation. For a circular bubble in static equilibrium, we explore the impacts of uniform grid resolution and bubble size on bubble shape, mass conservation, pressure jump and spurious currents. While the standard interFoam solver exhibits excellent mass conservation with errors below 0.1% on fine grids, it lacks the accuracy to predict reasonable physics for a bubble in microfluidic systems. At higher resolution, large spurious currents significantly displace and deform the bubble, which is oscillating with resolution dependent mode and frequency. Furthermore, the pressure jump is consistently underestimated by more than 10%. The solver phaseFieldFoam suffers from much larger mass losses of up to 2%, which decrease as the ratio between interface thickness and bubble diameter decreases provided the diffuse interface region is adequately resolved. Spurious currents are very low and the bubble remains circular preserving its initial position with an error in pressure jump below 1%.

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Simulation of micro-flow dynamics at low capillary numbers using adaptive interface compression

Cited by 25 publications

References 48 publications

Comparison of Surface Tension Models for the Volume of Fluid Method

Comparison of Surface Tension Models for the Volume of Fluid Method

Numerical Treatment of the Interface in Two Phase Flows Using a Compressible Framework in OpenFOAM: Demonstration on a High Velocity Droplet Impact Case

On suitability of phase-field and algebraic volume-of-fluid OpenFOAM® solvers for gas–liquid microfluidic applications

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