A multi-field two-fluid concept for transitions between different scales of interfacial structures

Experimental investigation on the initiation and flow development of gas-liquid slug two-phase flow in a horizontal pipe

Validation of closure models for interfacial drag and turbulence in numerical simulations of horizontal stratified gas–liquid flows

Simulations of free surface flows with implementation of surface tension and interface sharpening in the two-fluid model

CFD simulation of horizontal oil-water flow with matched density and medium viscosity ratio in different flow regimes

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-d...

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

Experimental and numerical prediction of horizontal stratified flows

Construction and execution of experiments at the multi-purpose thermal hydraulic test facility TOPFLOW for generic investigations of two-phase flows and the development and validation of CFD codes - Final report

In pressurised water reactors (PWR), different scenarios of small break Loss of Coolant Accident (LOCA) lead to the reflux-condenser mode in which steam enters the hot leg from the reactor pressure vessel (RPV) and condenses in the steam generator. In order to investigate the 2-phase flow behaviour in a complex reactor-typical geometry and to supply suitable data for CFD code validation, a model of the hot leg of a pressurised water reactor (PWR) was built at Forschungszentrum Dresden-Rossendorf (FZD). Experiments were performed during air/water counter-current flow before and around the onset of flooding. The measured global parameters like water levels and pressure drop will be analysed in order to characterise the flow. Furthermore, the comparison with detailed visual observations will be used to explain this behaviour. Finally, the onset of flooding as revealed by the data will be discussed in comparison to proposal of other investigators.

Counter-current Flow Limitation Experiments in a Model of the Hot Leg of a Pressurised Water Reactor

Geschichtete Zweiphasenstromungen wurden in zwei verschiedenen Modellen des heisen Strangs eines Druckwasserreaktors (DWR) untersucht, um experimentelle Daten fur die Entwicklung und Validierung von CFD-Codes (computational fluid dynamics) bereitzustellen. So wurde die lokale Stromungsstruktur mit einer Hochgeschwindigkeitskamera visualisiert. Daruber hinaus wurde eine der Testsektionen mit rechteckigem Querschnitt konstruiert, um optimale Beobachtungsbedingungen zu erreichen. Das Phanomen der Gegenstrombegrenzung wurde untersucht, das in manchen Unfallszenarien den Reflux-Condenser-Betrieb beeintrachtigen kann.

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Christophe Vallée

Papers

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

Experimental and numerical prediction of horizontal stratified flows

Construction and execution of experiments at the multi-purpose thermal hydraulic test facility TOPFLOW for generic investigations of two-phase flows and the development and validation of CFD codes - Final report

Counter-current Flow Limitation Experiments in a Model of the Hot Leg of a Pressurised Water Reactor

Experimental investigation of stratified two-phase flows in the hot leg of a PWR for CFD validation