The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform
M H W Hendrix - One of the best experts on this subject based on the ideXlab platform.
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analysis of time integration methods for the compressible two fluid Model for pipe flow simulations
International Journal of Multiphase Flow, 2017Co-Authors: Benjamin Sanderse, Ivar Eskerud Smith, M H W HendrixAbstract:Abstract In this paper we analyse different time integration methods for the Two-Fluid Model and propose the BDF2 method as the preferred choice to simulate transient compressible multiphase flow in pipelines. Compared to the prevailing Backward Euler method, the BDF2 scheme has a significantly better accuracy (second order) while retaining the important property of unconditional linear stability ( A -stability). In addition, it is capable of damping unresolved frequencies such as acoustic waves present in the compressible Model ( L -stability), opposite to the commonly used Crank–Nicolson method. The stability properties of the Two-Fluid Model and of several discretizations in space and time have been investigated by eigenvalue analysis of the continuous equations, of the semi-discrete equations, and of the fully discrete equations. A method for performing an automatic von Neumann stability analysis is proposed that obtains the growth rate of the discretization methods without requiring symbolic manipulations and that can be applied without detailed knowledge of the source code. The strong performance of BDF2 is illustrated via several test cases related to the Kelvin–Helmholtz instability. A novel concept called Discrete Flow Pattern Map (DFPM) is introduced which describes the effective well-posed unstable flow regime as determined by the discretization method. Backward Euler introduces so much numerical diffusion that the theoretically well-posed unstable regime becomes numerically stable (at practical grid and timestep resolution). BDF2 accurately identifies the stability boundary, and reveals that in the nonlinear regime ill-posedness can occur when starting from well-posed unstable solutions. The well-posed unstable regime obtained in nonlinear simulations is therefore in practice much smaller than the theoretical one, which might severely limit the application of the Two-Fluid Model for simulating the transition from stratified flow to slug flow. This should be taken very seriously into account when interpreting results from any slug-capturing simulations.
Benjamin Sanderse - One of the best experts on this subject based on the ideXlab platform.
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analysis of time integration methods for the compressible two fluid Model for pipe flow simulations
International Journal of Multiphase Flow, 2017Co-Authors: Benjamin Sanderse, Ivar Eskerud Smith, M H W HendrixAbstract:Abstract In this paper we analyse different time integration methods for the Two-Fluid Model and propose the BDF2 method as the preferred choice to simulate transient compressible multiphase flow in pipelines. Compared to the prevailing Backward Euler method, the BDF2 scheme has a significantly better accuracy (second order) while retaining the important property of unconditional linear stability ( A -stability). In addition, it is capable of damping unresolved frequencies such as acoustic waves present in the compressible Model ( L -stability), opposite to the commonly used Crank–Nicolson method. The stability properties of the Two-Fluid Model and of several discretizations in space and time have been investigated by eigenvalue analysis of the continuous equations, of the semi-discrete equations, and of the fully discrete equations. A method for performing an automatic von Neumann stability analysis is proposed that obtains the growth rate of the discretization methods without requiring symbolic manipulations and that can be applied without detailed knowledge of the source code. The strong performance of BDF2 is illustrated via several test cases related to the Kelvin–Helmholtz instability. A novel concept called Discrete Flow Pattern Map (DFPM) is introduced which describes the effective well-posed unstable flow regime as determined by the discretization method. Backward Euler introduces so much numerical diffusion that the theoretically well-posed unstable regime becomes numerically stable (at practical grid and timestep resolution). BDF2 accurately identifies the stability boundary, and reveals that in the nonlinear regime ill-posedness can occur when starting from well-posed unstable solutions. The well-posed unstable regime obtained in nonlinear simulations is therefore in practice much smaller than the theoretical one, which might severely limit the application of the Two-Fluid Model for simulating the transition from stratified flow to slug flow. This should be taken very seriously into account when interpreting results from any slug-capturing simulations.
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Simulation of Elongated Bubbles in a Channel Using the Two-Fluid Model
Journal of Dispersion Science and Technology, 2015Co-Authors: Benjamin Sanderse, M. Haspels, Ruud HenkesAbstract:This paper investigates the capability of the Two-Fluid Model to predict the bubble drift velocity of elongated bubbles in channels. The Two-Fluid Model is widely used in the oil and gas industry for dynamic multiphase pipeline simulations. The bubble drift velocity is an important quantity in predicting pipeline flushing and slug flow. In this paper, it is shown that the Two-Fluid Model in its standard form predicts a bubble drift velocity of (gH)^(1/2) (similar to the shallow water equations), instead of the exact value of 1/2(gH)^(1/2) as derived by Benjamin[1]. Modifying the Two-Fluid Model with the commonly employed momentum correction parameter leads to a steady solution (in a moving reference frame), but still predicts an erroneous bubble drift velocity. To get the correct bubble drift velocity, it is necessary to include the pressure variation along the channel height due to both the hydrostatic component and the vertical momentum flux.
Yufa He - One of the best experts on this subject based on the ideXlab platform.
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characteristic analysis of a non equilibrium thermodynamic two fluid Model for natural gas liquid pipe flow
Journal of Natural Gas Science and Engineering, 2017Co-Authors: Xia Wu, Changjun Li, Yufa HeAbstract:Abstract Natural Gas Liquid (NGL) primarily contains light hydrocarbon components, e.g., ethane, propane and iso-butane. Its unique phase behavior and rapid evaporation process typically causes a non-equilibrium thermodynamic two-phase flow in the transmission pipeline, in which the liquid and vapor phases have different temperatures at the same cross section of the pipe. To describe this two-phase flow, a one-dimensional Two-Fluid Model considering the NGL compressibility and viscosity is built based on the general mass, momentum and energy conservation equations for each phase. To select its appropriate solution method, the mathematical characteristic of the Model is studied using the eigenvalue analysis method. The results demonstrate that its mathematical characteristic is primarily dependent on the void fraction, densities and flow velocities of the liquid and vapor phases. The Two-Fluid Model is hyperbolic and well-posed when the liquid flow velocity is equal to the vapor flow velocity, the two-phase flow reduces to a single phase flow, or the difference between the liquid velocity and the vapor velocity is greater than the mixture sound speed. Otherwise, the Model is non-hyperbolic and ill-posed. Additionally, the results indicate that the numerical solution methods of the adiabatic Two-Fluid Model could be potentially extended to solve the non-equilibrium Two-Fluid Model for the NGL pipe flow.
Moon-sun Chung - One of the best experts on this subject based on the ideXlab platform.
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A modified semi-implicit method for a hyperbolic Two-Fluid Model
Applied Numerical Mathematics, 2009Co-Authors: Moon-sun ChungAbstract:By introducing the interfacial pressure jump terms based on a surface tension into the momentum equations of a two-phase Two-Fluid Model, the mathematical property of the governing equations is changed to a hyperbolic type. Then the eigenvalues of the equation system always become always real values representing the void wave and the pressure wave propagation speeds as shown in the present author's former article: Numerical Heat Transfer - Part B (40) (2001) 83-97. To solve the interfacial pressure jump terms with void fraction gradients implicitly, the conventional semi-implicit method should be modified by inserting an intermediate calculation process for a void fraction at a fractional time step. This modified semi-implicit method then becomes stable without conventional additive terms. Consequently, by including the interfacial pressure jump terms with the modified semi-implicit method, the numerical calculations of the void discontinuity propagation and water faucet problems can become more stable and sound than those calculated by using virtual mass terms.
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On the Characteristics of a Two-Dimensional Two-Fluid Model
ASME 2008 6th International Conference on Nanochannels Microchannels and Minichannels, 2008Co-Authors: Moon-sun ChungAbstract:In this study, we will suggest a two-dimensional Two-Fluid Model considering the effect of mass and momentum interactions to simulate more realistic two-phase flow than the conventional Model did. A hyperbolic Two-Fluid Model had been developed for one-dimensional two-phase flow by Chung et al. [1] and it has been improved and applied to analyze one-dimensional two-phase flow problem including surface tension effect for either ordinary pipe system or minichannels. However, in order to simulate the two-dimensional two-phase flow problem efficiently in the future, the above one-dimensional Model has need to be extended to two-dimensional equations and adopted to an upwind numerical method.Copyright © 2008 by ASME
P Poesio - One of the best experts on this subject based on the ideXlab platform.
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An experimental investigation and Two-Fluid Model validation for dilute viscous oil in water dispersed pipe flow
Experimental Thermal and Fluid Science, 2015Co-Authors: Davide Picchi, M. Demori, D. Strazza, Vittorio Ferrari, P PoesioAbstract:In this work we investigated high viscous oil in water dispersions (Do/w) in pipe. The experiments are performed in a 22.8-mm-id 9-m-long horizontal glass pipe using a high viscous oil (density of 886kg/m3and viscosity of 900mPas) and tap water as test fluids. Pressure gradients are collected; hold-up data are measured using the quick-closing-valves technique (QCV) and a capacitance sensor, specifically optimized for dispersed flows detection. A new Two-Fluid Model for liquid-liquid dispersed pipe flow to predict hold-up, pressure gradient, and the slip ratio between the liquid phases is presented. The experimental data are compared at first with homogeneous Model predictions. Then the presented Two-Fluid Model is validated against experimental data of this work and against experimental data taken from the literature showing a good agreement. The predicted and measured slip ratio is grater than unity for all oil-water dispersions investigated. © 2014 Elsevier Inc.
