Experimental data on vertical air-water pipe flow obtained by ultrafast electron beam X-ray tomography measurements

The qualification of CFD codes for two-phase flows requires reliable experimental data with high resolution in space and time. Especially data on the transient structure of the interface is required. Bubble sizes play an important role for the evolution of the flow along the flow path. Vertical pipe flow is suitable for model development and validation because of the well-defined boundary conditions and the possibility to observe the evolution of the flow along the pipe. In nuclear reactor safety research often flows with high void fraction have to be considered. Since optical measuring methods fail for such dense flows intrusive techniques as needle tip probes or wire-mesh sensors are frequently used. Due to the intrusive effect these techniques can be applied only for a limited range of flow conditions. This paper presents first quantitative results of measurements done in upwards vertical pipe flows with air-water and steam-water systems using the new non-intrusive ultrafast electron beam tomography.