A deterministic and viable coalescence model for Euler–Lagrange simulations of turbulent microbubble-laden flows

Hoppe, F.; Breuer, M.

doi:10.1016/j.ijmultiphaseflow.2017.10.009

Cited by 14 publications

(17 citation statements)

References 68 publications

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“…The Euler-Lagrange model is one of the most commonly used methods in the numerical simulation of microbubbles [32][33][34][35]. If the time step is small enough, the movement of a particle is considered uniform in that step.…”

Section: Euler-lagrange Modelmentioning

confidence: 99%

Large Eddy Simulation of Microbubble Drag Reduction in Fully Developed Turbulent Boundary Layers

Wang

Sun

et al. 2020

JMSE

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Microbubble drag reduction has good application prospects. It operates by injecting a large number of bubbles with tiny diameters into a turbulent boundary layer. However, its mechanism is not yet fully understood. In this paper, the mechanisms of microbubble drag reduction in a fully developed turbulent boundary layer over a flat-plate is investigated using a two-way coupled Euler-Lagrange approach based on large eddy simulation. The results show good agreement with theoretical values in the velocity distribution and the distribution of fluctuation intensities. As the results show, the presence of bubbles reduces the frequency of bursts associated with the sweep events from 637.8 Hz to 611.2 Hz, indicating that the sweep events, namely the impacting of high-speed fluids on the wall surface, are suppressed and the streamwise velocity near the wall is decreased, hence reducing the velocity gradient at the wall and consequently lessening the skin friction. The suppression on burst frequency also, with the fluid fluctuation reduced in degree, decreases the intensity of vortices near the wall, leading to reduced production of turbulent kinetic energy.

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Section: Euler-lagrange Modelmentioning

confidence: 99%

Large Eddy Simulation of Microbubble Drag Reduction in Fully Developed Turbulent Boundary Layers

Wang

Sun

et al. 2020

JMSE

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“…The capabilities of the four-way coupled model are evaluated in upward and downward channel flows of water at Reτ = 150, and results for bubble collision and coalescence efficiency analysed. It should be noted that previous work [33] has indicated that bubble break-up is negligible in low Reynolds number channel flows of the order of that studied in this work, and hence it is not considered further in this work. A summary of the key findings of the work and general conclusions are provided in Section 4.…”

Section: Introductionmentioning

confidence: 99%

“…Most numerical studies [23,33,34] of microbubble coalescence have focused on surfactantladen flows and it is well known that tiny amounts of contaminants or surfactants can drastically modify the air-water interface behaviour [35]. Experimental results reveal that clean air bubbles coalesce within milliseconds, much faster than when contaminants are present.…”

Section: Introductionmentioning

confidence: 99%

Simulation of Microbubble Dynamics in Turbulent Channel Flows

Zhai

Fairweather

Colombo

2020

Flow Turbulence Combust

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This work investigates microbubble dynamics in four-way (with coalescence) coupled microbubble-laden turbulent channel flows. Upward and downward flows of water at a shear Reynolds number of Reτ = 150 are predicted using direct numerical simulation (DNS).Microbubbles, assumed to be non-deformable and spherical, are injected into the water flow and tracked using a Lagrangian approach. One-way and two-way coupled predictions were successfully compared against other available DNS-based results and used to demonstrate different trends in bubble preferential motion, with bubbles pushed by the lift force towards the wall in upflow and towards the centre of the channel in downflow. Four-way coupled simulations with bubble coalescence clearly demonstrate that the presence of the bubbles, and collisions between them, have a non-negligible effect on the fluid phase. Analysis of bubble collision behaviour highlights that binary collisions most frequently occur at very small approach angles and with low relative approach velocities. Once a collision is detected, the occurrence of bubble coalescence is evaluated, with special attention given to the performance of different bubble coalescence models. The film drainage model returns a 100% coalescence efficiency, while on the other hand the energy model returns a 0% coalescence efficiency, with this large discrepancy requiring further investigation and model development. The knowledge gained from the present results on the mechanisms that underpin bubble collisions is of value to the further development of more advanced coalescence closure models.

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“…Four-way coupled simulations, accounting for interaction and collision in the dispersed phase field, have been addressed with Eulerian-Lagrangian techniques, but mainly for multiphase solid particle flows [1][2][3][4][5]. More recent and limited have been applications to dispersed bubbly flows [6][7][8]. These have been most often addressed using averaged Eulerian-Eulerian multi-fluid models, where evolution of the average bubble size distribution is predicted using population balance models.…”

Section: Introductionmentioning

confidence: 99%

Microbubble coalescence and breakup in turbulent vertical channel flows

Asiagbe

Fairweather

Njobuenwu

et al. 2018

Proceeding of THMT-18. Turbulence Heat and Mass Transfer 9 Proceedings of the Ninth International Symposium on Turbulence Heat

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Large eddy simulation coupled to Lagrangian bubble tracking is used to study four-way coupled turbulent bubbly flow in channels, including bubble collision, coalescence and breakup. Upward and downward vertical channel flows of water at shear Reynolds numbers of 150 and 2000 are examined, with air bubbles of diameter = 220 m dispersed within the flows. Additional simulations are performed for the case of refrigerant R134a at a shear Reynolds number of 1154. The ability of the model to predict coalescence and breakup is evaluated, as well as the impact of the flow condition on the two phenomena. Coalescence and breakup are favoured in upflow conditions, with turbulence found to significantly impact the level of bubble interaction. Coalescence is dominant at low turbulence levels and breakup, which was only detected in the R134a flow, is favoured at high turbulence. The results demonstrate the capabilities of the overall model to predict bubble coalescence and breakup, and its usefulness for predicting flows that are of industrial relevance where interfacial area and bubble size distribution govern interfacial mass, momentum and heat transfer processes.

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A deterministic and viable coalescence model for Euler–Lagrange simulations of turbulent microbubble-laden flows

Cited by 14 publications

References 68 publications

Large Eddy Simulation of Microbubble Drag Reduction in Fully Developed Turbulent Boundary Layers

Large Eddy Simulation of Microbubble Drag Reduction in Fully Developed Turbulent Boundary Layers

Simulation of Microbubble Dynamics in Turbulent Channel Flows

Microbubble coalescence and breakup in turbulent vertical channel flows

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