Research on bulbous bow ships1

Model tests were carried out to determine the still water performance of a 24,000 DWT bulk carrier, provided with a large bulbous bow of hemi-spherical form. A comparison of the results with those of the same ship model, however, with conventional bow was made both for the loaded and ballast condition. Considerable savings in power were found for the ship with bulbous bow in the ballast condition. In the loaded condition practically no influence of the bulbous bow could be established. The results were checked on possible laminar flow effects by carrying out additional tests with extra turbulence stimulators. Flow observation by underwater television and flow tests with paint showed that separation of flow on the forebody did not occur. Overshoot manoeuvring tests have indicated that the manoeuvrability of the ship model is hardly affected by fitting the bulbous bow. A comparison of the maximum rates of change of heading at given rudder angles shows that there is only a very slight difference between the values of the model with conventional bow and those of the model with bulbous bow, which means that the bulbous bow has practically no effect on the directional stability either.