scholarly journals The impact of the order of numerical schemes on slug flows modeling

2019 ◽  
Vol 23 (6 Part B) ◽  
pp. 3855-3864
Author(s):  
Azizi Zolfaghary ◽  
Mohammad Naghashzadegan ◽  
Vahid Shokri
Keyword(s):  
Truncation Error ◽  
Fluid Model ◽  
Second Order ◽  
Numerical Schemes ◽  
Third Order ◽  
First Order ◽  
Solution Field ◽  
Two Fluid Model ◽  
The Impact ◽  
Two Fluid

This paper aims to explore the impact of the order of numerical schemes on the simulation of two-phase slug flow with a two-fluid model initiation. The governing equations of the two-fluid model have been solved by a class of Riemann solver. The numerical schemes applied in this paper involve first-order (Lax-Friedrichs and Rusanov), second-order (Ritchmyer), and high-order (flux-corrected transport or FCT and total variance diminishing or TVD). The results suggest that the TVD and FCT are able to predict the slug initiation with high accuracy compared with experimental results. Lax-Friedrichs and Rusanov are both first-order schemes and have second-order truncation error. This second-order truncation error caused numerical diffusion in the solution field and could not predict the slug initiation with high accuracy in contrast to TVD and FCT schemes. Ritchmyer is a second-order scheme and has third-order truncation error. This third-order truncation error caused dispersive results in the solution field and was not a proper scheme.

Two-Phase Flows in Mini-/Micro-Gas Flow Channels of PEM Fuel Cells

2013 ◽  
Author(s):  
Sung Chan Cho ◽  
Yun Wang
Keyword(s):  
Pressure Drop ◽  
Gas Flow ◽  
Fluid Model ◽  
Pem Fuel Cells ◽  
Two Phase ◽  
Micro Gas Flow ◽  
Two Fluid Model ◽  
The Impact ◽  
Two Fluid ◽  
Phase Pressure

In this paper, two-phase flow dynamics in a micro channel with various wall conditions are both experimentally and theoretically investigated. Annulus, wavy and slug flow patterns are observed and location of liquid phase on different wall condition is visualized. The impact of flow structure on two-phase pressure drop is explained. Two-phase pressure drop is compared to a two-fluid model with relative permeability correlation. Optimization of correlation is conducted for each experimental case and theoretical solution for the flows in a circular channel is developed for annulus flow pattern showing a good match with experimental data in homogeneous channel case.

scholarly journals Comparison of well-posedness criteria of two-fluid models for numerical simulation of gas-liquid two-phase flows in vertical pipes

2021 ◽  
pp. 158-158
Author(s):  
Naghibi Falahati ◽  
V. Shokri ◽  
A. Majidian
Keyword(s):  
Fluid Model ◽  
Well Posedness ◽  
Fluid Models ◽  
Vertical Pipe ◽  
Numerical Diffusion ◽  
Solution Field ◽  
Two Fluid Model ◽  
Two Phases ◽  
Well Posed ◽  
Two Fluid

The purpose of the present study is to compare the well-posedness criteria of the free-pressure two-fluid model, single-pressure two-fluid model, and two-pressure two-fluid model in a vertical pipe. Two-fluid models were solved using the Conservative Shock Capturing Method. A water faucet case is used to compare two-fluid models. The free pressure two-fluid model can accurately predict discontinuities in the solution field if the problem's initial condition satisfies the Kelvin Helmholtz instability conditions. The single-pressure two-fluid model can accurately predict the behavior of flows in which the two phases are poorly coupled. The two-pressure two-fluid model is an unconditionally well-posed one; if in the free-pressure two-fluid model and single-pressure two-fluid model, the range of velocity difference of two phases exceeds certain limits, the models will be ill-posed. The two-pressure two-fluid model produces more numerical diffusion than the free-pressure two-fluid and single-pressure two-fluid models in the solution field. High numerical diffusion of two-pressure two-fluid models leads to failure to better comply with the problem's analytical solution. Results show that a single-pressure model is a powerful model for numerical modeling of gas-liquid two-fluid flows in the vertical pipe due to a broader range of well-posed than free-pressure models and less numerical diffusion than the two-pressure model.

Modeling Interfacial Interactions and Turbulence in the Near-Wall Region of a Vertical Bubbly Boundary Layer

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
Jamel Chahed ◽  
Lucien Masbernat
Keyword(s):  
Boundary Layer ◽  
Void Fraction ◽  
Fluid Model ◽  
Second Order ◽  
Turbulence Closure ◽  
Wall Region ◽  
Turbulence Structure ◽  
Two Fluid Model ◽  
Two Fluid ◽  
Near Wall

Abstract A two-fluid model with second-order turbulence closure is used for the simulation of a turbulent bubbly boundary layer. The turbulence model is based on the decomposition of the Reynolds stress tensor in the liquid phase into two parts: a turbulent part and a pseudo-turbulent part. The reduction in second-order turbulence closure in the near-wall region is interpreted according to a modified wall logarithmic law. Numerical simulations of bubbly boundary layer developing on a vertical flat plate were performed in order to analyze the bubbles effect on the liquid turbulence structure and to evaluate the respective roles of turbulence and of interfacial forces in the near-wall distribution of the void fraction. The two-fluid model with the second-order turbulence closure succeeds in reproducing the diminution of the turbulent intensity observed in the near-wall region of bubbly boundary layer and the increase in turbulence outside the boundary layer. The analysis of the interfacial force in the near-wall zone has led to the development of relatively simple formulation of the lift-wall force in the logarithmic zone that depends on dimensionless distances to the wall. After appropriate adjustment, this formulation makes it possible to reproduce the shape of the near-wall void fraction peaking observed in bubbly boundary layer experiments.

Large Eddy Simulation of Gas - Second Order Moment of Particle Approach for Riser

2013 ◽  
Vol 274 ◽  
pp. 596-599 ◽  
Author(s):  
Ju Hui Chen ◽  
Ting Hu ◽  
Jiu Ru Li
Keyword(s):  
Large Eddy Simulation ◽  
Fluid Model ◽  
Flow Behavior ◽  
Second Order ◽  
Order Moment ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Two Fluid Model ◽  
Two Fluid ◽  
Particle Approach

Flow behavior of gas and particles is performed by means of gas–solid two-fluid model with the large eddy simulation for gas and the second order moment for particles in the riser. This study shows that the computed solids volume fractions of two cases are compared with the experimental data using a two-dimensional model. The gas and solid velocity is computed.

scholarly journals Theoretical Study of Absorption of Light Due to Effect of Ponderomotive Force

2019 ◽  
Vol 5 (1) ◽  
pp. 91-96
Author(s):  
P. K. Thakur ◽  
J. J. Nakarmi
Keyword(s):  
Absorption Coefficient ◽  
Fluid Model ◽  
Motive Force ◽  
Lower Plasma ◽  
Third Order ◽  
Laser Plasma Interaction ◽  
Absorption Of Light ◽  
Tangential Forces ◽  
Two Fluid Model ◽  
Two Fluid

Absorption of light due to effect of ponder motive force in laser plasma interaction which has seen that the nonlinear interaction results from rigorous application of the ponder motive force description based on Lorentz’s theory. The deduced equation of motion is more general than that of the two–fluid model of the plasma and that used in the theory of microwave interaction with plasma. As might be expected, the forces are only in the direction of lower plasma densities and tangential forces vanish only with the general equation of two–fluid model. This result has been verified up to the third order in the spatial variation of the electron density. In addition it is seen that the collision frequency decreases continuously with the increase in temperature. From these results, it is concluded that the absorption coefficient decreases continuously with the increase in temperature. Furthermore, this work describes the variation of the absorption coefficient with laser light frequency and shows that the absorption coefficient depends on the frequency of light.

scholarly journals Effect of liquid phase compressibility on modeling of gas-liquid two-phase flows using two-fluid model

2019 ◽  
Vol 23 (5 Part B) ◽  
pp. 3003-3013
Author(s):  
Vahid Shokri ◽  
Kazem Esmaeili
Keyword(s):  
Liquid Phase ◽  
Relative Velocity ◽  
Numerical Study ◽  
Fluid Model ◽  
Shock Capturing ◽  
Two Phase ◽  
Solution Field ◽  
Two Fluid Model ◽  
Flow Variables ◽  
Two Fluid

In this paper, a numerical study is performed in order to investigate the effect of the liquid phase compressibility two-fluid model. The two-fluid model is solved by using conservative shock capturing method. At the first, the two-fluid model is applied by assuming that the liquid phase is incompressible, then it is assumed that in three cases called water faucet case, large relative velocity shock pipe case, and Toumi?s shock pipe case, the liquid phase is compressible. Numerical results indicate that, if an intense pressure gradient is governed on the fluid-flow, single-pressure two-fluid model by assuming liquid phase incompressibility predicts the flow variables in the solution field more accurate than single-pressure two-fluid model by assuming liquid phase compressibility.

CFL-Violating Numerical Schemes for a Two-Fluid Model

2005 ◽  
Vol 29 (1) ◽  
pp. 83-114 ◽  
Author(s):  
Steinar Evje ◽  
Tore Flåtten
Keyword(s):  
Fluid Model ◽  
Numerical Schemes ◽  
Two Fluid Model ◽  
Two Fluid
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