The fluid dynamic and the gas-liquid mass transfer characteristics of trickle-bed reactors were revisited and their quantification methods reevaluated based on extensive experimental historic flow databases (22,000 experiments) set up from the open literature published over the last 50 years. The state-of-the-art of trickle-bed fluid dynamics was summarized and a set of unified and updated estimation methods relying on neural network, dimensional analysis and phenomenological hybrid approaches were discussed.