General power-law temporal scaling for unequal-size microbubble coalescence

Chen, Rou; Yu, Huidan; Zeng, Jianhuan; Zhu, Likun

doi:10.1103/physreve.101.023106

Cited by 12 publications

(10 citation statements)

References 46 publications

(75 reference statements)

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“…1. In our previous study [34], a switching of the major axis of the coalescing bubble between the horizontal and vertical directions was observed, when the Oh number is relatively small, in the post-coalescence corresponding to the period from (c) to (g) in Fig. 1.…”

Section: Computational Set-upmentioning

confidence: 64%

“…The in-house, GPU-accelerated LBM code based on the free-energy model is used for all the simulation in this work. The reliability of this LBM model has been demonstrated in some application studies [30,35,34] previously through comparisons with analytical solutions and experimental/computational results. The spatial resolution was selected 600 2 through a convergence check [34].…”

Section: Computational Set-upmentioning

confidence: 92%

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Mechanism of damped oscillation in microbubble coalescence

Chen

Zeng

2019

Computers & Fluids

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This work is part of our continuous research effort to reveal the underlying physics of bubble coalescence in microfluidics through the GPU-accelerated lattice Boltzmann method. We numerically explore the mechanism of damped oscillation in microbubble coalescence characterized by the Ohnesorge (Oh) number. The focus is to address when and how a damped oscillation occurs during a coalescence process. Sixteen cases with a range of Oh numbers from 0.039 to 1.543, varying in liquid viscosity from 0.002 to 0.08kg/(m • s) correspondingly, are systematically studied. First, a criterion of with or without damped oscillation has been established. It is found that a larger Oh enables faster/slower bubble coalescence with/without damped oscillation when (Oh < 0.477)/(Oh > 0.477) and the fastest coalescence falls at Oh ≈ 0.477. Second, the mechanism behind damped oscillation is explored in terms of the competition between driving and resisting forces. When Oh is small in the range of Oh < 0.477, the energy dissipation due to viscous effect is insignificant, sufficient surface energy initiates a strong inertia and overshoots the neck movement. It results in a successive energy transformation between surface energy and kinetic energy of the coalescing bubble. Through an analogy to the conventional damped harmonic oscillator, the saddle-point trajectory over the entire oscillation can be well predicted analytically.

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Section: Computational Set-upmentioning

confidence: 64%

Section: Computational Set-upmentioning

confidence: 92%

Mechanism of damped oscillation in microbubble coalescence

Chen

Zeng

2019

Computers & Fluids

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“…The novelty of this computational approach consists of (1) a unique extraction of flow domain and local wall normality from image data, (2) a seamless connection between the output of image processing and the input of CFD, (3) an en-route calculation of strain-rate tensor for wall stresses, and (4) GPU parallel computing processing 29 – 32 (not included in this paper) to significantly mitigate the computation burden. The kinetic-based lattice Boltzmann modeling has emerged for simulating a broad class of complex flows including pore-scale porous media flow 33 – 37 , multiphase/multicomponent flows 38 – 42 , and turbulence 40 , 43 – 47 . The main advantages related to this work are its amenability for modeling the intermolecular interactions at the two-phase interface to recover the appropriate multiphase dynamics without demanding computing cost and its suitability for scalable GPU (Graphics Processing Unit) parallelization 29 , 31 , 32 , 40 , 43 – 48 to achieve fast computation.…”

Section: Introductionmentioning

confidence: 99%

Volumetric lattice Boltzmann method for wall stresses of image-based pulsatile flows

Zhang

Gomez-Paz

Chen

et al. 2022

Sci Rep

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Image-based computational fluid dynamics (CFD) has become a new capability for determining wall stresses of pulsatile flows. However, a computational platform that directly connects image information to pulsatile wall stresses is lacking. Prevailing methods rely on manual crafting of a hodgepodge of multidisciplinary software packages, which is usually laborious and error-prone. We present a new computational platform, to compute wall stresses in image-based pulsatile flows using the volumetric lattice Boltzmann method (VLBM). The novelty includes: (1) a unique image processing to extract flow domain and local wall normality, (2) a seamless connection between image extraction and VLBM, (3) an en-route calculation of strain-rate tensor, and (4) GPU acceleration (not included here). We first generalize the streaming operation in the VLBM and then conduct application studies to demonstrate its reliability and applicability. A benchmark study is for laminar and turbulent pulsatile flows in an image-based pipe (Reynolds number: 10 to 5000). The computed pulsatile velocity and shear stress are in good agreements with Womersley's analytical solutions for laminar pulsatile flows and concurrent laboratory measurements for turbulent pulsatile flows. An application study is to quantify the pulsatile hemodynamics in image-based human vertebral and carotid arteries including velocity vector, pressure, and wall-shear stress. The computed velocity vector fields are in reasonably well agreement with MRA (magnetic resonance angiography) measured ones. This computational platform is good for image-based CFD with medical applications and pore-scale porous media flows in various natural and engineering systems.

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“…There have been many studies on the phenomenon and mechanism of bubble coalescence through experiments [11][12][13][14][15][16][17][18][19], theoretical analyses [12,20,21] and numerical simulations [14,[22][23][24][25][26][27][28][29][30][31]. Stover, et al [14] first investigated the turbulence characteristics of coalescence of bubbles with different sizes, viscosities, and surface tensions.…”

Section: Introductionmentioning

confidence: 99%

“…They simulated the bubble coalescence at a high-density ratio using LBM [24]. A similar approach, solving Navier-Stokes equations and Cahn-Hilliard interface evolution equation by LBM, was used by Chen, et al to study the coalescence of unequal-size or equal-size bubbles [25][26][27]. They presented power-law relations between the global coalescence time and size inequality, and the effect of the Ohnesorge (Oh) number on those power-law relations.…”

Section: Introductionmentioning

confidence: 99%

Thermodynamic non-equilibrium effects in bubble coalescence: A discrete Boltzmann study

Sun,

Gan,

et al. 2022

Preprint

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The Thermodynamic Non-Equilibrium (TNE) effects in the coalescing process of two initially static bubbles under thermal conditions are investigated by a Discrete Boltzmann Model (DBM).The spatial distributions of the typical none-quilibrium quantity, i.e., the Non-Organized Momentum Fluxes (NOMF) during evolutions are investigated in detail. The density-weighted statistical method is used to highlight the relationship between the TNE effects and the morphological or kinetics characteristics of bubble coalescence. It is found that the xx-component and yy-component of NOMF are anti-symmetrical; the xy-component changes from an anti-symmetric internal and external double quadrupole structure to an outer octupole structure during the coalescing process.More importantly, the evolution of the averaged xx-component of NOMF provides two characteristic instants, which divide the non-equilibrium process into three stages. The first instant corresponds to the moment when the mean coalescing speed gets the maximum and at this time the ratio of minor and major axes is about 1/2. The second instant corresponds to the moment when the ratio of minor and major axes gets 1 for the first time. It is interesting to find that the three quantities, TNE intensity, acceleration of coalescence and negative slope of boundary length, show a high degree of correlation and attain their maxima simultaneously. Surface tension and heat conduction accelerate the process of bubble coalescence while viscosity delays it. Both surface tension and viscosity enhance the global non-equilibrium intensity, whereas heat conduction restrains it. These TNE features and findings present some new insights into the kinetics of bubble coalescence.

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General power-law temporal scaling for unequal-size microbubble coalescence

Cited by 12 publications

References 46 publications

Mechanism of damped oscillation in microbubble coalescence

Mechanism of damped oscillation in microbubble coalescence

Volumetric lattice Boltzmann method for wall stresses of image-based pulsatile flows

Thermodynamic non-equilibrium effects in bubble coalescence: A discrete Boltzmann study

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