Closure relations for two-fluid models for two-phase stratified smooth and stratified wavy flows

2006 ◽  
Vol 32 (1) ◽  
pp. 82-105 ◽  
Author(s):  
A. Ullmann ◽  
N. Brauner
Keyword(s):  
Fluid Models ◽  
Two Phase ◽  
Closure Relations ◽  
Two Fluid

Modeling of Sodium Two-Phase Flow With the TRACE Code

2009 ◽  
Author(s):  
Aurelia Chenu ◽  
Konstantin Mikityuk ◽  
Rakesh Chawla
Keyword(s):  
Single Phase ◽  
Two Phase Flow ◽  
Flow Simulation ◽  
Phase Flow ◽  
Fluid Models ◽  
Code System ◽  
Two Phase ◽  
Liquid Flows ◽  
Transfer Mechanisms ◽  
Two Fluid

In the framework of PSI’s FAST code system, the TRACE thermal-hydraulics code is being extended for representation of sodium two-phase flow. As the currently available version (v.5) is limited to the simulation of only single-phase sodium flow, its applicability range is not enough to study the behavior of a Sodium-cooled Fast Reactor (SFR) during a transient in which boiling is anticipated. The work reported here concerns the extension of the two-fluid models, which are available in TRACE for steam-water, to sodium two-phase flow simulation. The conventional correlations for ordinary gas-liquid flows are used as basis, with optional correlations specific to liquid metal when necessary. A number of new models for representation of the constitutive equations specific to sodium, with a particular emphasis on the interfacial transfer mechanisms, have been implemented and compared with the original closure models. As a first application, the extended TRACE code has been used to model experiments that simulate a loss-of-flow (LOF) accident in a SFR. The comparison of the computed results, with both the experimental data and SIMMER-III code predictions, has enabled validation of the capability of the modified TRACE code to predict sodium boiling onset, flow regimes, dryout, flow reversal, etc. The performed study is a first-of-a-kind application of the TRACE code to two-phase sodium flow. Other integral experiments are planned to be simulated to further develop and validate the two-phase sodium flow methodology.

Closure relations for the shear stresses in two-fluid models for laminar stratified flow

2004 ◽  
Vol 30 (7-8) ◽  
pp. 877-900 ◽  
Author(s):  
A Ullmann ◽  
A Goldstein ◽  
M Zamir ◽  
N Brauner
Keyword(s):  
Stratified Flow ◽  
Shear Stresses ◽  
Fluid Models ◽  
Closure Relations ◽  
Two Fluid

Application of Number Density Transport Equation for the Recovery of Consistency in Multi-Field Model

2003 ◽  
Author(s):  
Akio Tomiyama ◽  
Naoki Shimada ◽  
Hiroyuki Asano
Keyword(s):  
Numerical Experiment ◽  
Transport Equation ◽  
Shape Factor ◽  
Field Model ◽  
Fluid Model ◽  
Fluid Models ◽  
Number Density ◽  
Two Phase ◽  
Closure Relations ◽  
Dispersed Flows

It is demonstrated through a thought numerical experiment that a conventional two- or multi-fluid model suffers from an inconsistency problem, by which it would fail in accurately predicting two-phase dispersed flows even with reliable closure relations for interfacial transfer terms. To overcome the inconsistency, a numerical method based on a number density transport equation and a shape factor for a fluid or solid particle is proposed. The (N+2)-field model (NP2 model) proposed in our previous studies [1]–[3] is adopted as the basis of the proposed method. It is confirmed that the method gives better predictions than conventional multi-fluid models and recovers the consistency.

First and Second-Order Accurate Schemes for Two-Fluid Models

1998 ◽  
Vol 120 (2) ◽  
pp. 363-368 ◽  
Author(s):  
Iztok Tiselj ◽  
Stojan Petelin
Keyword(s):  
Two Phase Flow ◽  
Second Order ◽  
Minor Role ◽  
Phase Flow ◽  
Fluid Models ◽  
Two Phase ◽  
Large Computer ◽  
Wide Range ◽  
Fast Transients ◽  
Two Fluid

The six-equation two-fluid model of two-phase flow taken from the RELAP5/MOD3 computer code has been used to simulate three simple transients: a two-phase shock tube problem, the Edwards Pipe experiment, and water hammer due to rapid valve closure. These transients can be characterized as fast transients, since their characteristic time-scales are determined by the sonic velocity. First and second-order accurate numerical methods have been applied both based on the well-known, Godunov-type numerical schemes. Regarding the uncertainty of the two-fluid models in today’s large computer codes for the nuclear thermal-hydraulics, use of second-order schemes is not always justified. While this paper shows the obvious advantage of second-order schemes in the area of fast transients, first-order accurate schemes may still be sufficient for a wide range of two-phase flow transients where the convection terms play a minor role compared to the source terms.

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