VERIFICATION OF MODELS FOR BUBBLE TURBULENT DIFFUSION AND BUBBLE DIAMETER IN MULTI-DIMENSIONAL TWO-FLUID MODEL

2002 ◽  
Author(s):  
AKIRA OHNUKI ◽  
HAJIME AKIMOTO
Keyword(s):  
Turbulent Diffusion ◽  
Fluid Model ◽  
Bubble Diameter ◽  
Verification Of Models ◽  
Two Fluid Model ◽  
Two Fluid

Assessment of Components of the Subcooled Boiling Model for CFD Simulations

2010 ◽  
Author(s):  
Deoras Prabhudharwadkar ◽  
Martin A. Lopez de Bertodano ◽  
John Buchanan ◽  
Avinash Vaidheeswaran
Keyword(s):  
Fluid Model ◽  
Constitutive Relations ◽  
Bubble Diameter ◽  
Density Ratio ◽  
Data Sets ◽  
Vapor Generation ◽  
Wide Range ◽  
Two Fluid Model ◽  
Bubble Sizes ◽  
Two Fluid

This paper describes the details of validation of heat and mass transfer models used for subcooled boiling simulation with a CFD two-fluid model. This research was focused on assessment of the wall heat flux partitioning model using the state-of-the-art multidimensional experimental data available in the literature. Various constitutive relations used to close the vapor generation rate at the heated wall were studied and the best suited combination of these was obtained. The current study was restricted to vertical flows through pipe and annulus geometries. Three data sets from the literature were considered: first with R12 at about 26 bar pressure, second with water at atmospheric pressure and third with R113 at 2.69 bar pressure. In these data sets, the bubble diameter distribution across the ducts was measured. Bubble diameter estimation brings in the largest uncertainty in the two-fluid model predictions and hence using the data with known bubble sizes allowed to focus on assessment of other parameters which use constitutive relations to model vapor generation rate, e.g. bubble nucleation site density and bubble departure frequency at the wall. The simulations were carried out using the CFD code CFX-12. The R12 data used here corresponds to fluid-vapor density ratio which is equivalent to that of water-steam at 150 bar. Therefore the density ratio varies over two orders of magnitude. The surface tension also varies over a wide range from 0.0017 to 0.057 N/m. The ratio of the flow channel hydraulic diameter to the bubble diameter in these simulations varied between 4 and 40. The two-fluid model was modified, for cases involving bubble sizes too large to be represented using the continuum assumption, in order to obtain satisfactory results. Hence, the model that has been developed for this study is applicable for a wide range of physical conditions and bubble sizes.

scholarly journals Investigation on Bubble Diameter Distribution in Upward Flow by the Two-Fluid and Multi-Fluid Models

Energies ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5776
Author(s):  
Yongzhong Zeng ◽  
Weilin Xu
Keyword(s):  
Experimental Data ◽  
Volume Fraction ◽  
Fluid Model ◽  
Bubble Diameter ◽  
Diameter Distribution ◽  
Bubble Flow ◽  
Calculation Results ◽  
Two Fluid Model ◽  
Gas Volume ◽  
Two Fluid

Bubble flow can be simulated by the two-fluid model and the multi-fluid model based on the Eulerian method. In this paper, the gas phase was further divided into several groups of dispersed phases according to the diameter by using the Eulerian-Eulerian (E-E) multi-fluid model. The diameters of bubbles in each group were considered to be the same, and their distributions were reorganized according to a specific probability density function. The experimental data of two kinds of bubble flow with different characteristics were used to verify the model. With the help of the open-source CFD software, OpenFOAM-7.x (OpenFOAM-7.0, produced by OpenFOAM foundation, Reading, England), the influences of the group number, the probability distribution function, and the parameters of different bubble diameters on the calculation results were studied. Meanwhile, the numerical simulation results were compared with the two-fluid model and the experimental data. The results show that for the bubble flow with the unimodal distribution, both the multi-fluid model and the two-fluid model can obtain the distribution of gas volume fraction along the pipe radius. The calculation results of the multi-fluid model agree with the experimental data, while those of the two-fluid model differ greatly from the experimental data, which verifies the advantage of the multi-fluid model in calculating the distribution of gas volume fraction in the polydisperse bubble flow. Meanwhile, the multi-fluid model can be used to accurately predict the distribution of the parameters of each phase of the bubble flow if the reasonable bubble diameter distribution is provided and the appropriate interphase force calculation model is determined.

Phase Distribution in the Cap Bubble Regime in a Duct

2006 ◽  
Vol 128 (4) ◽  
pp. 811-818 ◽  
Author(s):  
Martin Lopez de Bertodano ◽  
Xiaodong Sun ◽  
Mamoru Ishii ◽  
Asim Ulke
Keyword(s):  
Turbulent Diffusion ◽  
Phase Distribution ◽  
Fluid Model ◽  
Three Dimensional ◽  
Interfacial Structure ◽  
Two Phase ◽  
Diffusion Force ◽  
Two Fluid Model ◽  
Bubble Regime ◽  
Two Fluid

The lateral phase distribution in the cap-bubbly regime was analyzed with a three-dimensional three-field two-fluid computational fluid dynamics (CFD) model based on the turbulence model for bubbly flows developed by Lopez de Bertodano et al. [1994, “Phase Distribution in Bubbly Two-Phase Flow in Vertical Ducts,” Int. J. Multiphase Flow, 20(5), pp. 805–818]. The turbulent diffusion of the bubbles is the dominant phase distribution mechanism. A new analytic result is presented to support the development of the model for the bubble induced turbulent diffusion force. New experimental data obtained by Sun et al. [2005, “Interfacial Structure in an Air-Water Planar Bubble Jet,” Exp. Fluids, 38(4), pp. 426–439] with the state-of-the-art four-sensor miniature conductivity probe in a vertical duct is used to validate the three-field two-fluid model CFD simulations.

scholarly journals Natural modes of the two-fluid model of two-phase flow

2021 ◽  
Vol 33 (3) ◽  
pp. 033324
Author(s):  
Alejandro Clausse ◽  
Martín López de Bertodano
Keyword(s):  
Two Phase Flow ◽  
Fluid Model ◽  
Phase Flow ◽  
Two Phase ◽  
Natural Modes ◽  
Two Fluid Model ◽  
Two Fluid

Self-consistent hydrodynamic two-fluid model of vortex plasma

2021 ◽  
Vol 33 (3) ◽  
pp. 037116
Author(s):  
Victor L. Mironov
Keyword(s):  
Fluid Model ◽  
Self Consistent ◽  
Two Fluid Model ◽  
Two Fluid

scholarly journals Mathematical study on two-fluid model for flow of K–L fluid in a stenosed artery with porous wall

2021 ◽  
Vol 3 (4) ◽  
Author(s):  
R. Ponalagusamy ◽  
Ramakrishna Manchi
Keyword(s):  
Theoretical Study ◽  
Fluid Model ◽  
Porous Wall ◽  
Governing Equations ◽  
Rate Of Increase ◽  
Special Cases ◽  
Stenosed Artery ◽  
Flow Through ◽  
Two Fluid Model ◽  
Two Fluid

AbstractThe present communication presents a theoretical study of blood flow through a stenotic artery with a porous wall comprising Brinkman and Darcy layers. The governing equations describing the flow subjected to the boundary conditions have been solved analytically under the low Reynolds number and mild stenosis assumptions. Some special cases of the problem are also presented mathematically. The significant effects of the rheology of blood and porous wall of the artery on physiological flow quantities have been investigated. The results reveal that the wall shear stress at the stenotic throat increases dramatically for the thinner porous wall (i.e. smaller values of the Brinkman and Darcy regions) and the rate of increase is found to be 18.46% while it decreases for the thicker porous wall (i.e. higher values of the Brinkman and Darcy regions) and the rate of decrease is found to be 10.21%. Further, the streamline pattern in the stenotic region has been plotted and discussed.

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