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Experimental investigation and CFD simulation of horizontal air/water slug flow

  • Christophe Vallée , Thomas Höhne , Horst-Michael Prasser and Tobias Sühnel
Published/Copyright: March 26, 2013
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Kerntechnik
From the journal Kerntechnik Volume 71 Issue 3

Abstract

For the investigation of air/water slug flow, a horizontal channel with rectangular cross-section was built at Forschungszentrum Rossendorf. The channel allows the investigation of air/water co- and counter-current flows at atmospheric pressure, especially the slug behaviour. Optical measurements were performed with a high-speed video camera, and were complemented by simultaneous dynamic pressure measurements. Moreover velocity-fields were measured using Particle Image Velocimetry (PIV). A CFD simulation of the stratified co-current flow was performed using the code CFX-5, applying the Euler-Euler two fluid model with the free surface option. The grid contains 4105 control volumes. The turbulence was modelled separately for each phase using the k- based shear stress transport (SST) turbulence model. To achieve wave generation in such a short channel, the inlet water level had to be varied in time. For this purpose, the water level history was taken from a recorded image sequence and set as time-dependent boundary condition at the model inlet. The results show a wave formation up to slug development with closure of the whole channel cross-section and consequently an increase of the pressure level behind the slug. Despite unsteady conditions at the inlet of the test channel and simplified initial conditions in the model, the slug simulation with CFX is in good qualitative agreement with the experiment, while the slug length increases during its progression, witch was not observed in reality.

Kurzfassung

Ein horizontaler Strömungskanal mit rechteckigem Querschnitt wurde am Forschungszentrum Rossendorf für die Untersuchung von Luft/Wasser Schwallströmungen errichtet. An diesem Kanal können Luft/Wasser-Strömungen bei Atmosphärendruck untersucht werden, wobei sowohl Gleich- als auch Gegenstromverhältnisse eingestellt werden können. Spezielles Untersuchungsobjekt ist die Schwallströmung. Es wurden optische Messungen mit einer Hochgeschwindigkeits-Videokamera durchgeführt, die durch die synchrone Messung des dynamischen Druckes ergänzt wurden. Zudem wurden Geschwindigkeitsfelder über PIV (Particle Image Velocimetry) ermittelt. Die CFD Simulation des geschichteten Gleichstroms wurde mit dem Code CFX-5 durchgeführt, bei Anwendung des Euler-Euler Zweifluid-Modells mit freier Oberfläche. Das Gitter enthielt 4105 Zellen. Das Turbulenzmodell wurde mittels dem k- basierenden SST-Modell (shear stress transport) für jede Phase getrennt angewendet. Um eine Wellenströmung in einem so kurzen Kanal generieren zu können, musste am Kanaleintritt der Füllstand zeitlich variiert werden. Hierfür wurde durch Auswertung einer aufgenommenen Bildsequenz der Füllstand gemessen und als zeitabhängige Randbedingung am Modelleintritt gesetzt. Die Ergebnisse zeigen eine Wellen- und Schwallbildung mit kompletter Versperrung des Kanalquerschnittes und demzufolge einen Anstieg des Druckes hinter dem Schwall. Trotz instationärer Bedingungen am Eintritt der Teststrecke und vereinfachter Anfangs-Bedingungen im Modell, stimmt die Schwallsimulation mit CFX qualitativ gut mit den Experimenten überein, obwohl die Länge des berechneten Schwalls in Laufrichtung zunimmt, was in Wirklichkeit nicht beobachtet wurde.

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Received: 2005-11-15
Published Online: 2013-03-26
Published in Print: 2006-05-01

© 2006, Carl Hanser Verlag, München

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  3. Summaries/Kurzfassungen
  4. Summaries
  5. Technical Contributions/Fachbeiträge
  6. Current use of probabilistic safety evaluations for advanced reactor concepts
  7. Experiments and comparing calculations on thermohydraulic pressure surges in pipes
  8. Experimental investigation and CFD simulation of horizontal air/water slug flow
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https://doi.org/10.3139/124.100281

Articles in the same Issue

  1. Contents/Inhalt
  2. Contents
  3. Summaries/Kurzfassungen
  4. Summaries
  5. Technical Contributions/Fachbeiträge
  6. Current use of probabilistic safety evaluations for advanced reactor concepts
  7. Experiments and comparing calculations on thermohydraulic pressure surges in pipes
  8. Experimental investigation and CFD simulation of horizontal air/water slug flow
  9. Uncertainty and sensitivity analysis of the CPS-CC voiding in the RBMK reactor Ignalina-2
  10. Irradiation damages in tantalum spallation target
  11. Multigroup neutron reflection and leakage conditions for axial core models with anisotropic scattering
  12. Performance analyses of the pool-top radiation level reduction systems at the ETRR-2 research reactor
  13. An interpretation procedure for the purpose of incorporation monitoring during decommissioning of nuclear reactors
  14. Thermal hydraulics of the fixed bed nuclear reactor concept
  15. Technical Note
  16. The critical slab problem for linearly anisotropic scattering and reflecting boundary conditions with the HN method
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