A new algorithm for segmentation of ultrafast X-ray tomo-graphed gas-liquid flows

The ultrafast electron beam X-ray computed tomography was developed during the last years to obtain detailed data on two-phase flows. In a recent study we investigated different gas-liquid flow regimes in a vertical pipe at the Transient Two-phase Flow test facility (TOPFLOW). The study includes experiments on gas-liquid flows with varied superficial velocities for both phases and different flow directions. The obtained data is required for understanding fundamental physics of two-phase flow phenomena and for the development and validation of CFD codes. To extract quantitative data from the reconstructed three-dimensional data array, a new segmentation algorithm was developed, due the results of existing segmentation algorithms aren't satisfyingly. The originality of this new algorithm bases on a stepwise creation of new bubbles using pixel agglomeration in shrinking steps without defining markers or starting points. The results were compared with threshold and gradient methods using two different bubble phantoms and real two-phase flow measurements. The new algorithm shows the best qualitative and quantitative results. (authors)