Flow Loop for X-Ray CT Imaging of Sand Transport

摘要

Two closed circuit flow loops have been constructed for X-ray CT imaging of multiphase flows. A 3rd generation helical scanner provides 3D images with a voxel size as small as 0.35x0.35x0.30mm. By “folding” the loops, flows have been imaged over a 16m section of 3.8 cm (1- 1/2”) pipe. In future, larger bores could be accommodated with a shorter overall length, dictated by the aperture and weight limit of the scanner. Sand slurry flows have been imaged in both laminar and turbulent regimes (using silicone oil and water, respectively) over a range of velocities reflective of typical in situ pressure gradients. Flowing sand concentrations up to 20% by volume were achieved by adjusting the total sand content in the loop. With proper calibration the CT images provide detailed, quantitative measures of sand concentration and, indirectly, the partitioning between moving and settled regions of the flow. The flowing density profiles vary significantly with the sand content and flow velocity, indicative of changing sand transport mechanisms. Fluctuations over the observable length of the loop show evidence of settling overlaid on the flow-induced resuspension. The effects of the end loops on both aspects of sand transport are considered.