Objectives The effects of air flow rate, sailing angle within the groove bottom of the air layer retention and energy efficiency were studied.

Methods The study focuses on a large-scale scale model of a bulk carrier. By designing a air layer drag reduction self-propelled model system and a hull cavity scheme, drag reduction experiments were conducted under open water conditions using the self-propelled model. The research examines the jet drag reduction effect on the model in a positive floating attitude of ship, as well as the impact of a certain trim angle on the speed and shaft power of the model..

Results When the host speed is in certain, it can significantly improve the model speed with air injection, and after stopping the jet the air layer within the air cavity of ship bottom can be maintained for a long time; it will get better drag reduction efficiency when the ship in the upright state and the trimming is within 0.25 degrees. When the trimming angle is too larger, the gas will overflows from both sides of the model head, and the air layer cannot effectively cover the bottom of the ship, so it will decrease the efficiency of the drag reduction.

Conclusions Through experiments, some meaningful conclusions have been obtained, which can provide a certain reference for the engineering application of air layer drag reduction technology on full-formed ships.