Influence of Rotational and Translational Oscillations on the Drainage of Liquid in Floating Packed Beds

A marinization test rig comprising a hexapod/column/wire-mesh-sensor assemblage was used to emulate the liquid drainage onboard floating packed columns. Single and compounded rotations and translations of tilting (roll, roll + pitch) and non-tilting (yaw, sway, heave, sway + heave) types were implemented on the robot to allow measurements of time-resolved local free-draining liquid saturation and drainage rates for various oscillation amplitudes and periods of the moving packed bed. The liquid drainage evolution highlighted, irrespective of the hexapod configuration, a succession of rapid and slow discharge stages disjointed by an abrupt short-lived transition with zero net liquid drainage rates. The gravity characteristic time, by dwarfing the periods of the sine wave excitations, singled out the oscillating gravitational force as the main factor behind the change of the liquid drainage response, whereas the influence of the moving-frame fictitious acceleration was minor. Drainage under rotational oscillations mainly depended on the instantaneous bed inclinations, thereby impacting the instantaneous partition of the liquid between the column lowermost and uppermost zones. The prominent role of gravity at the expense of robot acceleration was also corroborated by the invariance of the liquid drainage profiles with respect to non-tilting equal-period oscillations, which barely deviated from the drainage profile of a static vertical column.