Hydrodynamics of gas-liquid cocurrent downflow in floating packed beds

An innovative experimental setup combining a robot with six-degree-of-freedom motions (translational: surge, sway, heave, and rotational: roll, pitch, yaw) and an embarked column instrumented with a capacitance wire mesh sensor was built to investigate experimentally the two-phase flow hydrodynamics in porous media within inclined stationary and oscillating packed beds under gas-liquid cocurrent descending flows. The hydrodynamic deviations with respect to the stationary straight column were thoroughly analyzed in terms of bed pressure drop, liquid saturation, regime changeover, and pulse flow properties. Non-tilting oscillations had marginal effects on the packed bed hydrodynamics which remained practically similar to the one prevailing in stationary vertical trickle beds. Conversely, tilting oscillations profoundly influenced the flow regime inside the packed bed as a result of the time-dependent nature of the gravitational and inertial (acceleration/deceleration) forces brought about by the hexapod rotational oscillations which caused important secondary transverse displacements of the fluids in the bed. Using moment analysis of the probability density functions of the registered liquid saturation time series, it was found that due to the periodic gravity-driven stratification, the transition to pulse flow shifted towards higher fluid velocities as the oscillation periods of roll or roll+pitch motions were increased.