LOCAL VOID FRACTION AND FLUID VELOCITY MEASUREMENTS IN A CAPILLARY CHANNEL WITH A SINGLE OPTICAL PROBE

An experimental investigation was performed in air-water bubbly flow to study the liquid turbulence spectra in a 200mm diameter vertical pipe. A dual optical probe was used to measure the local void fraction and bubble diameter while the liquid velocities were measured using hot-film anemometry. Experiments were performed at two liquid superficial velocities of 0.2 and 0.68m/s for gas superficial velocities in the range of 0 to 0.18m/s. Generally, as the void fraction increases there is a turbulence augmentation. However, a turbulence suppression was observed near the pipe wall at the higher liquid flow rate for low void fraction. In the augmentation case, the turbulence spectra showed a significant increase in the energy at the wave number range comparable to the bubble diameter. In the suppression case, the spectra showed that suppression initially occurs at the low wave number range and then extends to higher wave numbers as suppression increased.

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Near-bottom sediment concentration and fluid velocity measurements on the inner continental shelf, New York

Journal of Geophysical Research Atmospheres ◽

10.1029/jc083ic12p06052 ◽

1978 ◽

Vol 83 (C12) ◽

pp. 6052 ◽

Cited By ~ 44

Author(s):

J. W. Lavelle ◽

R. A. Young ◽

D. J. P. Swift ◽

T. L. Clarke

Keyword(s):

New York ◽

Continental Shelf ◽

Bottom Sediment ◽

Fluid Velocity ◽

Sediment Concentration ◽

Velocity Measurements ◽

Inner Continental Shelf

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Optical probe for high-temperature local void fraction determination

Applied Optics ◽

10.1364/ao.21.000886 ◽

1982 ◽

Vol 21 (5) ◽

pp. 886 ◽

Cited By ~ 10

Author(s):

M. A. Vince ◽

H. Breed ◽

G. Krycuk ◽

R. T. Lahey

Keyword(s):

High Temperature ◽

Void Fraction ◽

Optical Probe ◽

Fraction Determination

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Revised partial coupling in fluid–particulate systems

The Journal of Computational Multiphase Flows ◽

10.1177/1757482x18791885 ◽

2018 ◽

Vol 10 (4) ◽

pp. 215-227

Author(s):

Husam A Elghannay ◽

Danesh K Tafti

Keyword(s):

Void Fraction ◽

Stokes Equations ◽

Fluid Velocity ◽

Particle Interaction ◽

Point Mass ◽

Mass Force ◽

Source Terms ◽

Convergence Behavior ◽

Full Coupling ◽

Partial Coupling

Fluid equations in Computational Fluid Dynamics coupled with Discrete Element Method (CFD-DEM) simulations solve the volume-averaged Navier–Stokes equations. Full coupling between the dispersed phase and continuous phase is made by the exchange of source terms as well as the void fraction. The void fraction is calculated from the presence of the particles in the computational fluid cells while the source terms are calculated from the point mass force models of the fluid–particle interaction forces. Dense particulate system with large spatiotemporal variations in the void fraction shows hard convergence behavior. This can impact the robustness of the solver during the time integration process. One option is to use partial coupling by neglecting the explicit effect of void fraction in the fluid momentum equations while retaining its effect on force models. Although the partial coupling is more stable and shows better convergence behavior, the mobility of the particles is found to be reduced as compared to the full-coupling approach. In the current work, we propose a revised partial coupling in which a modified fluid velocity is used in point mass force models to compensate for the omission of the void fraction in the fluid governing equations. The effectiveness of this method is demonstrated in a fluidized bed and in sediment transport simulations. In both cases it is shown that the use of the proposed method gives very good comparisons with the fully coupled simulations while reducing the fluid calculation time by factors ranging from 1.35 to 4.35 depending on the flow conditions. The revised partial coupling is not recommended as a substitute for full coupling in dense systems but as an alternate approach when full coupling leads to numerical difficulties.

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Correlation between Void Fraction and Two-Phase Flow Pattern Air-Water with Low Viscosity in Mini Channel with Slope 30 Degrees

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.846.289 ◽

2020 ◽

Vol 846 ◽

pp. 289-295

Author(s):

Sukamta ◽

Sudarja

Keyword(s):

Void Fraction ◽

High Speed ◽

Two Phase Flow ◽

Fluid Velocity ◽

Flow Patterns ◽

Superficial Velocity ◽

Working Fluid ◽

Phase Flow ◽

Two Phase ◽

Void Fractions

Two-phase flow has been used in so many industrial processes, such as boilers, reactors, heat exchangers, geothermal and others. Some parameters which need to be studied include flow patterns, void fractions, and pressure changes. Research on void fractions aims to determine the composition of the gas and liquid phases that will affect the nature and value of the flow property. The purpose of this study is to find out the characteristics of the void fraction of various patterns that occurs and to determine the characteristics of the velocity, length, and frequency of bubbly and plug. Data acquisition was used to convert the data from analog to digital so that it can be recorded, stored, processed, and analyzed. High-speed camera Nikon type J4 was used to record the flow. The condition of the study was adiabatic with variation of superficial gas velocity (JG), superficial fluid velocity (JL), and also working fluid. To determine the void fraction by using the digital image processing method. The results of the study found that the flow patterns which occurred in this study were bubbly, plug, annular, slug-annular and churn flows. It also showed that the void fraction value is determined by the superficial velocity of the liquid and air. The higher the superficial velocity of the air, the lower the void fraction value.

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