The effects of nanoparticles on the lift force and drag force on bubbles in nanofluids: A two-fluid model study

Two-fluid model can simulate two phase flow less computational cost than inter-face tracking method and particle interaction method. Therefore, two-fluid model is useful for thermal hydraulic analysis in large-scale domain such as a rod bundle. Japan Atomic Energy Agency (JAEA) develops three dimensional two-fluid model analysis code ACE-3D, which adopts boundary fitted coordinate system in order to simulate complex shape channel flow. In this paper, boiling two-phase flow analysis in a tight lattice rod bundle is performed by ACE-3D code. The parallel computation using 126CPUs is applied to this analysis. In the results, the void fraction, which distributes in outermost region of rod bundle, is lower than that in center region of rod bundle. At height z = 0.5 m, void fraction in the gap region is higher in comparison with that in center region of the subchannel. However, at height of z = 1.1m, higher void fraction distribution exists in center region of the subchannel in comparison with the gap region. The tendency of void fraction to concentrate in the gap region at vicinity of boiling starting point, and to move into subchannel as water goes through rod bundle, is qualitatively agreement with the measurement results by neutron radiography. To evaluate effects of two-phase flow model used in ACE-3D code, numerical simulation of boiling two-phase in tight lattice rod bundle with no lift force model (neglecting lift force acting on bubbles) is also performed. From the comparison of numerical results, it is concluded that the effects of lift force model are not so large on overall void fraction distribution in tight lattice rod bundle. However, higher void fraction distribution in center region of the subchannel was not observed in this simulation. It is concluded that the lift force model is important for local void fraction distribution in rod bundles.

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Effect of interfacial drag force on the numerical stability of the two-step method in the two-fluid model

Nuclear Engineering and Design ◽

10.1016/0029-5493(91)90031-c ◽

1991 ◽

Vol 126 (3) ◽

pp. 427-438 ◽

Cited By ~ 3

Author(s):

Jae Young Lee ◽

Hee Cheon No

Keyword(s):

Drag Force ◽

Numerical Stability ◽

Fluid Model ◽

Step Method ◽

Two Fluid Model ◽

Interfacial Drag ◽

Two Fluid

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Effect of microstructural anisotropy on the fluid–particle drag force and the stability of the uniformly fluidized state

Journal of Fluid Mechanics ◽

10.1017/jfm.2012.425 ◽

2012 ◽

Vol 713 ◽

pp. 27-49 ◽

Cited By ~ 6

Author(s):

William Holloway ◽

Jin Sun ◽

Sankaran Sundaresan

Keyword(s):

Friction Coefficient ◽

Drag Force ◽

Fluid Model ◽

Stokes Number ◽

Spherical Particles ◽

Force Model ◽

Drag Model ◽

Fluidized State ◽

Two Fluid Model ◽

Two Fluid

AbstractLattice-Boltzmann simulations of fluid flow through sheared assemblies of monodisperse spherical particles have been performed. The friction coefficient tensor extracted from these simulations is found to become progressively more anisotropic with increasing Péclet number, $Pe= \dot {\gamma } {d}^{2} / D$, where $\dot {\gamma } $ is the shear rate, $d$ is the particle diameter, and $D$ is the particle self-diffusivity. A model is presented for the anisotropic friction coefficient, and the model constants are related to changes in the particle microstructure. Linear stability analysis of the two-fluid model equations including the anisotropic drag force model developed in the present study reveals that the uniformly fluidized state of low Reynolds number suspensions is most unstable to mixed mode disturbances that take the form of vertically travelling waves having both vertical and transverse structures. As the Stokes number increases, the transverse-to-vertical wavenumber ratio decreases towards zero; i.e. the transverse structure becomes progressively less prominent. Fully nonlinear two-fluid model simulations of moderate to high Stokes number suspensions reveal that the anisotropic drag model leads to coarser gas–particle flow structures than the isotropic drag model.

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Computational Fluid Dynamic- Two Fluid Model Study of Gas-Solid Heat Transfer in a Riser with Various Inclination Angles

International Journal of Engineering ◽

10.5829/idosi.ije.2017.30.04a.02 ◽

2017 ◽

Vol 30 (4) ◽

Keyword(s):

Heat Transfer ◽

Computational Fluid Dynamic ◽

Fluid Model ◽

Fluid Dynamic ◽

Model Study ◽

Inclination Angles ◽

Two Fluid Model ◽

Two Fluid

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Interfacial Drag Force Improvement in Two-Fluid Model

Volume 6A: Thermal-Hydraulics and Safety Analyses ◽

10.1115/icone26-81070 ◽

2018 ◽

Author(s):

Longxiang Zhu ◽

Jianqiang Shan

Keyword(s):

Drag Coefficient ◽

Void Fraction ◽

Drag Force ◽

Fluid Model ◽

Bubble Radius ◽

Interfacial Area ◽

Low Flow ◽

Two Fluid Model ◽

Interfacial Drag ◽

Two Fluid

Interfacial drag force, which indicates the momentum transfer between liquid phase and vapor phase, is a key constitutive equation in the two-fluid model. Based on the “drift-velocity approach” (utilized in RELAP5/MOD3) and the “drag coefficient approach” (utilized in RELAP5/MOD2 and CTF), three improvements are proposed, which are: 1) improved drag coefficient closure, 2) improved drag coefficient formulation approach, 3) improved bubble radius closure approach. The comparison among the two original approaches and the three improved approaches has been made with the ORNL experiment data in high pressure-low flow condition and the results have been discussed. Results indicates: 1) the EPRI correlation predicts the void fraction worse than the drag coefficient approaches; 2) the drag coefficient correlations in CTF predicts the void fraction better than improved drag coefficient formulation approach, which are the original equations in Ishii’s model; 3) the improved drag coefficient formulation approach predicts similarly with the original RELAP5/MOD2 correlations, though it gets rid of the dependence on interfacial area concentration; 4) improved bubble radius closure approach over-predicts the void fraction, however more experiment tests should be calculated before a conclusion is drawn.

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