X-Ray tomography reconstruction of multiphase flows and the verification of CFD

Experimental studies using an X-ray tomography system were performed on a 4-inch horizontal section of the multiphase flow loop at NEl for gas–water and gas–oil–water flows. Values of liquid holdup and water liquid ratio are reported alongside analysis of the phase linear fraction through the crosssection of the pipe. The X-ray system revealed areas of gas entrainment and separation of oil and water which are not evident from high-speed video footage. The flow pattern of the tests was stratified-wavy, and computational fluid dynamics (CfD) analysis was performed using the volume of fluid (VOf) method. The prediction of liquid holdup and gas distribution through the pipe height as determined by CfD, correlated well with that determined by X-ray tomography. however, the results suggest that a transient VOf with a high-order mesh resolution is required to account for gas entrainment. This study shows that an X-ray system can be utilised to provide quantifiable validation data which are of value to multiphase models in CfD and provide insight that is not apparent during high-speed video analysis. The data generated from this system will be of considerable value to multiphase flow specialists and instrumentation developers.