Lift and drag coefficients of deformable bubbles in intense turbulence determined from bubble rise velocity

Three-phase flow formed in a disrupted core of nuclear reactors is one of the key phenomena to be simulated in reactor safety analysis. Particle-based simulation could be a powerful CFD tool to understand and clarify local thermal-hydraulic behaviors involved in such three-phase flows. In the present study, to develop a computational framework for three-phase flow simulations, a single bubble moving in a stagnant solid particle-liquid mixture pool was simulated using the finite volume particle (FVP) method. The simulations were carried out in a two dimensional system. The bubble shape change and the bubble rise velocity were compared with the newly performed experiments, which used solid particulate glasses of 0.9 mm in diameter, liquid silicone and air. The two-phase flow simulation of a single bubble rising in a stagnant liquid pool reproduced measured bubble shape and bubble rise velocity reasonably. On the other hand, the bubble rise velocity in a stagnant particle-liquid mixture pool was overestimated in comparison with the measurement. This result suggests that particle-particle and particle-fluid interactions would have dominant influence on bubble motion behavior in the particle-liquid mixture pool under the present multiphase conditions. To evaluate such interactions in the simulations, the particle-particle interactions were modeled by the distinct element method (DEM), while two models were applied to represent particle-fluid interactions. One is the theoretical model for apparent viscosity of particle-liquid mixture, which describes the viscosity increase of liquid mixed with solids based on the Frankel-Acrivos equation. The other is the drag force model for solid-fluid interactions. In the present study, we took the Gidaspow drag correlation, which is a combination of the Ergun equation and Wen-Yu equation. A comparison of both the transient bubble shape and bubble rise velocity between the results of experiment and simulation demonstrates that the present computational framework based on the FVP method and solid-phase interaction models is useful for numerical simulations of a single bubble moving in a stagnant solid particle-liquid mixture pool.

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Bubble rise velocity in two-dimensional fluidized beds

Powder Technology ◽

10.1016/0032-5910(95)02993-c ◽

1995 ◽

Vol 84 (3) ◽

pp. 283-285 ◽

Cited By ~ 16

Author(s):

Dinesh Gera ◽

Mridul Gautam

Keyword(s):

Fluidized Beds ◽

Two Dimensional ◽

Rise Velocity ◽

Bubble Rise ◽

Bubble Rise Velocity

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COMPUTATIONAL FLUID DYNAMICS SIMULATIONS OF TAYLOR BUBBLE RISE IN FLOWING LIQUIDS

JOURNAL OF THE NIGERIAN SOCIETY OF CHEMICAL ENGINEERS ◽

10.51975/21360205.som ◽

2021 ◽

Vol 36 (2) ◽

pp. 35-42

Author(s):

H.A Abubakar

Keyword(s):

Finite Element ◽

Fluid Dynamic ◽

Total Curvature ◽

Rise Velocity ◽

Systematic Analysis ◽

Taylor Bubble ◽

Bubble Rise ◽

Bubble Rise Velocity ◽

Bubble Rising ◽

Dynamics Simulations

Systematic analysis of the effect of gravitational, interfacial, viscous and inertia forces acting on a Taylor bubble rising in flowing liquids characterised by the dimensionless Froude (Uc), inverse viscosity (Nf ) and Eötvös numbers (Eo) is carried out using computational fluid dynamic finite element method. Particular attention is paid to cocurrent (i.e upward) liquid flow and the influence of the characterising dimensionless parameters on the bubble rise velocity and morphology analysed for Nf, Eo and Uc ranging between [40, 100], [20, 300] and [−0.20, 0.20], respectively. Analysis of the results of the numerical simulations showed that the existing theoretical model for the prediction of Taylor bubble rise velocity in upward flowing liquids could be modified to accurately predict the rise velocity in liquids with high viscous and surface tension effects. Furthermore, the mechanism governing the change in morphology of the bubble in flowing liquids was shown to be the interplay between the viscous stress and total curvature stress at the interface. Keywords: Taylor bubble, finite element, slug flow, CFD, rise velocity

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Bubble Rise Velocity and Surface Mobility in Aqueous Solutions of Sodium Dodecyl Sulphate and n-Propanol

Minerals ◽

10.3390/min9120743 ◽

2019 ◽

Vol 9 (12) ◽

pp. 743

Author(s):

Pavlína Basařová ◽

Yuliya Kryvel ◽

Jakub Crha

Keyword(s):

Surface Tension ◽

Aqueous Solutions ◽

Sodium Dodecyl Sulphate ◽

Sodium Dodecyl ◽

Bubble Surface ◽

Rise Velocity ◽

Bubble Rise ◽

Spherical Bubble ◽

Surface Mobility ◽

Bubble Rise Velocity

Aqueous solutions of simple alcohols exhibit many anomalies, one of which is a change in the mobility of the bubble surface. This work aimed to determine the effect of the presence of another surface-active agent on bubble rise velocity and bubble surface mobility. The motion of the spherical bubble in an aqueous solution of n-propanol and sodium dodecyl sulphate (SDS) was monitored by a high-speed camera. At low alcohol concentrations (xP < 0.01), both the propanol and SDS molecules behaved as surfactants, the surface tension decreased and the bubble surface was immobile. The effect of the SDS diminished with increasing alcohol concentrations. In solutions with a high propanol content (xP > 0.1), the SDS molecules did not adsorb to the phase interface and thus, the surface tension of the solution was not reduced with the addition of SDS. Due to the rapid desorption of propanol molecules from the bottom of the bubble, a surface tension gradient was not formed. The drag coefficient can be calculated using formulas for the mobile surface of a spherical bubble.

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