Turbulence and Phase Distribution in Bubbly Pipe Flow Under Microgravity Condition

2002 ◽  
Vol 124 (4) ◽  
pp. 951-956 ◽  
Author(s):  
J. Chahed ◽  
C. Colin ◽  
L. Masbernat
Keyword(s):  
Void Fraction ◽  
Pipe Flow ◽  
Phase Distribution ◽  
Fluid Model ◽  
Microgravity Condition ◽  
Added Mass ◽  
Mass Force ◽  
Void Fraction Distribution ◽  
Fraction Distribution ◽  
Two Fluid Model

The role of the turbulence in the void fraction distribution in bubbly pipe flow under microgravity condition is evaluated on the basis of numerical simulations using a Eulerian-Eulerian two-fluid model. In microgravity, the average relative velocity is weak and the void fraction distribution is mainly governed by the turbulence. The simulations show that the turbulent contributions of the added mass force play an important role in the phase distribution phenomenon. It is clearly proved that the turbulence acts on the bubbles distribution not only by the pressure term but also by the turbulent correlations obtained by averaging the added mass force.

New Two-Fluid Model Near-Wall Averaging and Consistent Matching for Turbulent Bubbly Flows

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Avinash Vaidheeswaran ◽  
Deoras Prabhudharwadkar ◽  
Paul Guilbert ◽  
John R. Buchanan ◽  
Martin Lopez de Bertodano
Keyword(s):  
Void Fraction ◽  
Fluid Model ◽  
Bubbly Flows ◽  
Wall Region ◽  
Two Phase ◽  
Void Fraction Distribution ◽  
Fraction Distribution ◽  
Two Fluid Model ◽  
Two Fluid ◽  
Near Wall

A new two-fluid model averaging in the near-wall region is proposed to ensure consistent matching of the two-phase k–ε turbulence model with the two-phase logarithmic law of the wall (Marie J. L., Moursali, E., and Tran-Cong, S., 1997, “Similarity Law and Turbulence Intensity Profiles in a Bubbly Boundary Layer,” Int. J. Multiphase Flow, 23(2), pp. 227–247). The void fraction distribution obtained with the averaging procedure is seen to conform to the two-phase wall function approach which is based on a double step function void fraction distribution. In particular, the proposed averaging technique is shown to achieve grid convergence in the near-wall region, which could not be obtained otherwise. Computational fluid dynamics (CFD) results with the proposed technique are in good agreement with experiments on upward bubbly flows over a flat plate, and upward and downward flows in pipes. An additional advantage of the proposed technique is that it replaces the wall force model, which has a significant degree of uncertainty in turbulent flow modeling, with a simpler geometric constraint.

Numerical Simulation of Boiling Two-Phase Flow in Tight-Lattice Rod Bundle by 3-Dimensional Two-Fluid Model Code ACE-3D

2008 ◽  
Author(s):  
Hiroyuki Yoshida ◽  
Takeharu Misawa ◽  
Kazuyuki Takase
Keyword(s):  
Void Fraction ◽  
Lift Force ◽  
Fluid Model ◽  
Phase Flow ◽  
Two Phase ◽  
Rod Bundle ◽  
Fraction Distribution ◽  
Two Fluid Model ◽  
Tight Lattice ◽  
Two Fluid

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.

Effect of void fraction covariance on two-fluid model based code calculation in pipe flow

2018 ◽  
Vol 108 ◽  
pp. 319-333 ◽  
Author(s):  
Tetsuhiro Ozaki ◽  
Takashi Hibiki ◽  
Shuichiro Miwa ◽  
Michitsugu Mori
Keyword(s):  
Void Fraction ◽  
Pipe Flow ◽  
Fluid Model ◽  
Model Based ◽  
Two Fluid Model ◽  
Two Fluid
Sign in / Sign up

Export Citation Format

Share Document