Macroscopic Formulation of Two-Phase Flows: The Two-Fluid Model

2015 ◽  
pp. 25-56
Author(s):  
Christophe Morel
Keyword(s):  
Fluid Model ◽  
Two Phase Flows ◽  
Two Phase ◽  
Two Fluid Model ◽  
Two Fluid

Interfacial Pressure Coefficient for Ellipsoids and Its Effect on the Two-Fluid Model Eigenvalues

2016 ◽  
Vol 138 (8) ◽  
Author(s):  
Avinash Vaidheeswaran ◽  
Martin Lopez de Bertodano
Keyword(s):  
Fluid Model ◽  
Pressure Coefficient ◽  
Well Posedness ◽  
Virtual Mass ◽  
Two Phase Flows ◽  
Two Phase ◽  
Pressure Coefficients ◽  
Interfacial Pressure ◽  
Two Fluid Model ◽  
Two Fluid

Analytical expressions for interfacial pressure coefficients are obtained based on the geometry of the bubbles occurring in two-phase flows. It is known that the shape of the bubbles affects the virtual mass and interfacial pressure coefficients, which in turn determines the cutoff void fraction for the well-posedness of two-fluid model (TFM). The coefficient used in the interfacial pressure difference correlation is derived assuming potential flow around a perfect sphere. In reality, the bubbles seen in two-phase flows get deformed, and hence, it is required to estimate the coefficients for nonspherical geometries. Oblate and prolate ellipsoids are considered, and their respective coefficients are determined. It is seen that the well-posedness limit of the TFM is determined by the combination of virtual mass and interfacial pressure coefficient used. The effect of flow separation on the coefficient values is also analyzed.

Numerical Study of Two-Phase Flow in a Horizontal Pipeline Using an Unconditionally Hyperbolic Two-Fluid Model

2018 ◽  
Author(s):  
Raphael V. N. de Freitas ◽  
Carina N. Sondermann ◽  
Rodrigo A. C. Patricio ◽  
Aline B. Figueiredo ◽  
Gustavo C. R. Bodstein ◽  
...  
Keyword(s):  
Volume Fraction ◽  
Numerical Study ◽  
Fluid Model ◽  
Momentum Conservation ◽  
Design Stage ◽  
Two Phase Flows ◽  
Two Phase ◽  
Efficient Manner ◽  
Two Fluid Model ◽  
Two Fluid

Numerical simulation is a very useful tool for the prediction of physical quantities in two-phase flows. One important application is the study of oil-gas flows in pipelines, which is necessary for the proper selection of the equipment connected to the line during the pipeline design stage and also during the pipeline operation stage. The understanding of the phenomena present in this type of flow is more crucial under the occurrence of undesired effects in the duct, such as hydrate formation, fluid leakage, PIG passage, and valve shutdown. An efficient manner to model two-phase flows in long pipelines regarding a compromise between numerical accuracy and cost is the use of a one-dimensional two-fluid model, discretized with an appropriate numerical method. A two-fluid model consists of a system of non-linear partial differential equations that represent the mass, momentum and energy conservation principles, written for each phase. Depending on the two-fluid model employed, the system of equations may lose hyperbolicity and render the initial-boundary-value problem illposed. This paper uses an unconditionally hyperbolic two-fluid model for solving two-phase flows in pipelines in order to guarantee that the solution presents physical consistency. The mathematical model here referred to as the 5E2P (five equations and two pressures) comprises two equations of continuity and two momentum conservation equations, one for each phase, and one equation for the transport of the volume fraction. A priori this model considers two distinct pressures, one for each phase, and correlates them through a pressure relaxation procedure. This paper presents simulation cases for stratified two-phase flows in horizontal pipelines solved with the 5E2P coupled with the flux corrected transport method. The objective is to evaluate the numerical model capacity to adequately describe the velocities, pressures and volume fraction distributions along the duct.

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