Rapid imaging of fluid flow patterns in a narrow packed bed using MRI.

A gradient echo rapid velocity and acceleration imaging sequence (GERVAIS) has been developed and implemented to image liquid flow within a narrow packed bed. Two-dimensional velocity images have been acquired with an in-plane pixel size of 781 microm x 781 microm, with a data acquisition time of 20 ms for a single velocity component. Images of the x, y and z velocity vectors are reported. Data are reported for Reynolds numbers (based on particle diameter) of 200 and 300. In each case, GERVAIS images are compared with the results of a standard spin-echo phase-encoding velocity measurement. At Re = 200, steady-state flow is expected and the velocity images acquired using both techniques are consistent. At Re = 300, the GERVAIS sequence is able to image the unsteady-state flow field within this system. In contrast, the standard phase-encoding velocity measurement contains significant artefacts.