scholarly journals Numerical Prediction of Bubbly Flow Around an Oscillating Hydrofoil by Incompressible Two-Fluid Model

2002 ◽  
Vol 8 (4) ◽  
pp. 295-304 ◽  
Author(s):  
TOMOMI UCHIYAMA
Keyword(s):  
Fluid Model ◽  
Bubbly Flow ◽  
Numerical Prediction ◽  
Two Fluid Model ◽  
Two Fluid

Transition of Bubbly Flow in Vertical Tubes: New Criteria Through CFD Simulation

2009 ◽  
Vol 131 (9) ◽  
Author(s):  
A. K. Das ◽  
P. K. Das ◽  
J. R. Thome
Keyword(s):  
Cfd Simulation ◽  
Fluid Model ◽  
Bubbly Flow ◽  
Transition Criteria ◽  
Balance Technique ◽  
Flow Through ◽  
Two Fluid Model ◽  
New Criterion ◽  
Vertical Tubes ◽  
Two Fluid

The two fluid model is used to simulate upward gas-liquid bubbly flow through a vertical conduit. Coalescence and breakup of bubbles have been accounted for by embedding the population balance technique in the two fluid model. The simulation enables one to track the axial development of the voidage pattern and the distribution of the bubbles. Thereby it has been possible to propose a new criterion for the transition from bubbly to slug flow regime. The transition criteria depend on (i) the breakage and coalescence frequency, (ii) the bubble volume count below and above the bubble size introduced at the inlet, and (iii) the bubble count histogram. The prediction based on the present criteria exhibits excellent agreement with the experimental data. It has also been possible to simulate the transition from bubbly to dispersed bubbly flow at a high liquid flow rate using the same model.

scholarly journals Behaviour and Stability of the Two-Fluid Model for Fine-Scale Simulations of Bubbly Flow in Nuclear Reactors

2015 ◽  
Vol 13 (4) ◽  
pp. 449-459 ◽  
Author(s):  
Henrik Ström ◽  
Srdjan Sasic ◽  
Klas Jareteg ◽  
Christophe Demazière
Keyword(s):  
Volume Fraction ◽  
Nuclear Reactors ◽  
Fluid Model ◽  
Bubbly Flow ◽  
Domain Size ◽  
Fuel Assemblies ◽  
Two Fluid Model ◽  
Liquid Flows ◽  
Two Fluid ◽  
Meso Scale

Abstract In the present work, we formulate a simplistic two-fluid model for bubbly steam-water flow existing between fuel pins in nuclear fuel assemblies. Numerical simulations are performed in periodic 2D domains of varying sizes. The appearance of a non-uniform volume fraction field in the form of meso-scales is investigated and shown to be varying with the bubble loading and the domain size, as well as with the numerical algorithm employed. These findings highlight the difficulties involved in interpreting the occurrence of instabilities in two-fluid simulations of gas-liquid flows, where physical and unphysical instabilities are prone to be confounded. The results obtained in this work therefore contribute to a rigorous foundation in on-going efforts to derive a consistent meso-scale formulation of the traditional two-fluid model for multiphase flows in nuclear reactors.

Numerical study on the bubbly flow around a hydrofoil in pitching and heaving motions

2003 ◽  
Vol 217 (7) ◽  
pp. 811-820 ◽  
Author(s):  
T Uchiyama
Keyword(s):  
Horizontal Plane ◽  
Numerical Study ◽  
Fluid Model ◽  
Bubbly Flow ◽  
The Finite Element Method ◽  
Flow Properties ◽  
Volumetric Fraction ◽  
Propulsive Performance ◽  
Two Fluid Model ◽  
Two Fluid

The air-water bubbly flow around a hydrofoil of NACA65-010, undergoing the heaving and pitching motions in the uniform flow on a horizontal plane, is simulated by an incompressible two-fluid model. The finite element method proposed in a prior paper is applied to solve the model. The Reynolds number defined by the volumetric velocity of the water is 10000 and the volumetric fraction of the air upstream of the hydrofoil, αg0, ranges from 0 to 0.06. The simulation reveals the effects of the αg0 value, the phase difference between the heaving and pitching motions, and the oscillating frequency. The propulsive performance is also discussed in relation to the time variation of the flow properties around the hydrofoil.

Numerical study on the propulsive performance of a wiggling blade in bubbly flow

2002 ◽  
Vol 216 (12) ◽  
pp. 1187-1196 ◽  
Author(s):  
T Uchiyama
Keyword(s):  
Numerical Study ◽  
Fluid Model ◽  
Bubbly Flow ◽  
The Finite Element Method ◽  
Flow Properties ◽  
Propulsive Performance ◽  
Time Variations ◽  
Two Fluid Model ◽  
Straight Conduit ◽  
Two Fluid

In order to search for an efficient propulsion mechanism in an air-water bubbly flow, the propulsive performance of a blade wiggling in the bubbly flow is analysed by a two-dimensional numerical method. The blade, whose geometry is similar to an NACA65–010 hydrofoil, is set in a straight conduit, in which the bubbly mixture flows. The wiggling motion is expressed by a progressive wave with reference to the swimming motions of fish. The bubbly flow is calculated by an incompressible two-fluid model in conjunction with the finite element method proposed by the author in an earlier paper. The calculations reveal the effects of a progressive waveform and volumetric fraction of air upstream of the blade on the propulsive performance of the blade. The time variations of the flow properties around the blade are also discussed in relation to the blade motion and propulsive performance.

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