Gain in Fuel Consumption with Frictional Resistance Reduction by Air-Bubbling Technique

The paper refers on a research activity developed at DREAMS Lab of the University of Genoa (Italy), focused on experimental application of air-bubbling technique on a hull model. With this method the injection of compressed air on the bottom of the model generates air bubbles modifying the boundary layer; measurements are implemented in towing tank. The hull model has got a large flat bottom that is particularly suitable to this application and a customized pneumatic circuit assembled to allow the injection of compressed air. The design of the pneumatic unit is made to perform tests in different operating conditions with a flexible distribution of air in different areas of the hull. Seven different operating conditions at three different levels of speed was measured at the towing tank with the goal to estimate the changes in local frictional drag at different levels of flow rate and pressure of injected air in different areas of the bottom. In particular the most favourable combination can reach a frictional resistance reduction about of 13%.This hull equipped with pneumatic circuit can be used in future to arrange new systematic experiments oriented to optimize the gain related to air bubbling technology.