Experimental research of air layer drag reduction on large-scale model

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 air injection device and control systems were designed for the experiment of air layer drag reduction on self-propelled model in open waters. 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 large ships.