Air Bubbles Displacement in Yield Stress Fluids

Naccache, Mônica F.; Abdu, Aline; Abreu, Carlos de

doi:10.29252/jafm.13.02.30261

Cited by 4 publications

(2 citation statements)

References 32 publications

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“…The higher viscosity levels are the reason for this behaviour. [ 109 ] The increased drag at higher viscosities reduces the velocity of the bubbles. Meanwhile, only sufficiently large bubbles have enough buoyancy to overcome the viscosity and drag effects, which is the reason for the larger bubble sizes (or higher velocity) at the top‐zone.…”

Section: Resultsmentioning

confidence: 99%

Bubble size distribution and gas holdup in bubble columns employing non‐Newtonian liquids: A CFD study

Paul

Pakzad

2022

Can J Chem Eng

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The hydrodynamics involved with the rise of air bubbles in shear‐thinning non‐Newtonian liquids in bubble columns was investigated using computational fluid dynamics (CFD). In bubble columns, the bubble size distribution (BSD) and gas holdup significantly affect the mass transfer rates and the reactor design. Consequently, the influence of superficial gas velocity, flow index, consistency index, sparger bubble size, and yield stress were analyzed on a local and global scale. The bubble sizes and the coalescence and breakage phenomena were incorporated using the homogeneous discrete method of the population balance model (PBM). The bubbles underwent coalescence during ascent and exhibited bimodal distribution. The radial homogeneity of the gas phase increased axially. Moreover, the zones of low liquid dynamic viscosity produced zones of a high gas holdup. Though the dual effect of viscosity on gas holdup was non‐existent, the gas holdup surged after 35.1 mPa s at the mid‐zone and remained constant thereafter. The noteworthy differences in simulation results put further emphasis upon the importance of sparger bubble size in CFD modelling. A decrease in the overall gas holdup and the axial air velocity with yield stress was observed. CFD simulation proved capable of providing results in reasonable agreement with experiments.

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Section: Resultsmentioning

confidence: 99%

Bubble size distribution and gas holdup in bubble columns employing non‐Newtonian liquids: A CFD study

Paul

Pakzad

2022

Can J Chem Eng

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“…The smaller the bubble is, the larger the gas-liquid relative area, which is conducive to the gas-liquid mass transfer process. However, when the bubble size changes, different rules can be elicited from the bubble rising trajectory (Naccache et al 2019). Bubble trajectory is also one of the important factors affecting heat and mass transfer.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study on Three-Dimensional Bubble Rising Behaviours by Virtual Stereo Vision

2023

JAFM

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This study addresses the measurement of three-dimensional (3D) bubble rising behaviour in still water with bubble equivalent diameters ranging from 2.61 mm to 5.11 mm using high-speed imaging and virtual stereo vision technology. The bubble shape, 3D trajectory/velocity, displacement angular frequency and terminal velocity of bubbles are analysed. The bubble equivalent diameter is obtained by the elliptic volume method. The bubbles are divided into small and large bubbles with a critical equivalent diameter of 4.49 mm, according to whether they are accompanied by deformation. The small bubbles (deq<4.49 mm) are spherical or ellipsoid, while the large bubbles (deq≥4.49 mm) exhibit ellipsoid, mushroom and hat shapes. The 3D trajectory is obtained by 3D reconstruction of bubble centroid coordinates. The rising trajectory of small bubbles shows 3D spiral motion, while the pitch increases gradually with the increase in the equivalent diameter. The trajectory of large bubbles is a two-dimensional (2D) zigzag. The bubble displacement curves in x- and z-directions are evaluated with third-order Fourier fitting. The results show that the bubble displacement frequency in the x and z-directions decreases with the increasing bubble diameter, and the displacement frequency in the xdirection is larger than that in the z-direction. The relative proportions of the viscous force, buoyancy, surface tension and inertial force on bubbles with different equivalent diameters are different, which leads to three trends in the vertical velocity of bubbles within the diameter range of this study. Finally, the bubble terminal velocity in still water is investigated. The terminal velocity first decreases and then increases with the increase in the equivalent diameter. The minimum value is 16.17 cm/s when the diameter of the bubble equivalent diameter is 4.49 mm. Moreover, the applicability of some classical prediction models is discussed.

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An experimental assessment of roll waves evolution in mud-like fluids flowing down steep slopes

Fiorot,

da R. Rocho,

Möller

et al. 2024

J Braz. Soc. Mech. Sci. Eng.

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Air Bubbles Displacement in Yield Stress Fluids

Cited by 4 publications

References 32 publications

Bubble size distribution and gas holdup in bubble columns employing non‐Newtonian liquids: A CFD study

Bubble size distribution and gas holdup in bubble columns employing non‐Newtonian liquids: A CFD study

Experimental Study on Three-Dimensional Bubble Rising Behaviours by Virtual Stereo Vision

An experimental assessment of roll waves evolution in mud-like fluids flowing down steep slopes

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