Investigation Of Influence Of Twin-bulbous-bow On Deep-vee Monohull's Resistance Performance

The deep-vee monohull widely used for surface ships generally has a sonar dome which is similar to a bulbous bow. The sonar dome may increase the resistance accidentally. As one of the most effective methods to reduce the wave resistance, the bulbous bow has been widely used for all types of commercial ships. A study by the Navy's David Taylor Model Basin estimates that fitting a drag-reduction bulbous bow onto Arleigh Burke (DDG-51) class destroyer could reduce its total resistance, but there are few warships using the technology to reduce resistance in domestic. In order to study the effect of twin-bulbous-bow on the navigation performance of warships, the computational fluid dynamics method is used to calculate the performance of original deep-vee monohull and deep-vee monohull with twin-bulbous-bow in calm water and regular waves.Firstly, the standard surface ship model DTMB5415 is selected for the study, and the computational fluid dynamics software STAR-CCM+ is used to simulate the process of captive and free model moving forward with a definite speed in calm water. By means of selecting appropriate grid refinement area and physical model, the numerical results of flow field, resistance and navigating state is coincided with experiment results, proving the accuracy of numerical computation method for simulating the condition of deep-vee monohull sailing in calm water, so an accurate numerical calculation method is determined.Then, three different shapes of drag-reduction bulbous bow are designed, and nine different installation positions for each drag-reduction bulbous bow are also designed to study the effect of various types of twin-bulbous-bow on the navigation performance of deep-vee monohull. The results show that, for each drag-reduction bulbous bow, the more forward relative to the hull and the more closer to the water surface of the installation location has the better drag-reduction effect.Furthermore, the paper investigates the affection of three types of twin-bulbous-bows,whose drag-reduction bulbous bow installs in the optimum position, on the navigation performance of deep-vee monohull at other speeds. The enhancive drag-reduction bulbous bow produces favorable interaction to ship's wakes based on the theory of waveform superimposition, reducing the dissipation of wave-making energy. At each speed, three types of twin-bulbous-bow all have significant drag-reduction effect with little affection on the sailing posture of hull, improving the ship navigation performance.Finally, DTMB5512 is selected, and STAR-CCM+ is also used to simulate the process of the model moving forward with a definite speed in regular waves,the numerical results agree well with experimental results. On this basis, the effect of twin-bulbous-bow on the navigation performance of deep-vee monohull sailing in regular waves is studied. The results show that not all twin-bulbous-bows have the expected the drag-reduction effect due to the complexity of the waves.