This paper describes the full scale experiment using air lubrication method to reduce the frictional resistance. The full scale experiment with the cement carrier Pacific Seagull was conducted from January to March, 2008. Torque and thrust are decreased due to the effect of bubbles. If we assume the value of thrust deduction is constant with and without bubbles, the effect of bubbles in reducing frictional resistance or ship resistance is clearly proved by the experimental results. The maximum total resistance reduction in case of ballast condition and full load condition are about 11% and 6% respectively. The mean propeller inflow velocity was increased for with air lubrication from no air condition due to the viscous resistance reduction. This phenomenon was considered using very simple boundary layer method.
Air lubrication method is a promising method to reduce frictional resistance which is nearly 70% of total resistance of low speed ship. Bubbles were injected at the fore bottom part of the ship. After injection, it is expected that bubbles will cover all the bottom part downstream and take effect on local frictional resistance reduction. In 2002, the full-scale experiment was carried out in SR 239 project for the first time using the training ship Sein-maru. The net energy saving in that experiment was 2% at air injection rate 40 m3Three years later, in 2005, the second full-scale experiment was done using the cement carrier Pacific Seagull. This ship has a box shape hull and was equipped with blowers which could be used to supply air for bubbles. However, injected bubbles did not cover the bottom of ship sufficiently so maximum frictional resistance reduction was only 1% at air injection of 50 m3Based on the results and accumulation of experience obtained from/min (Kodama et al. 2007). /min. Based on this result, the effect of bubbles on frictional resistance reduction of ship was proved (Nagamatsu et al. 2003).
