When the propellers are free from cavitation, such as submarines at diving depth, the radiating noises due to the propeller unsteady forces dominate. The simulations for hydrodynamics including stern wakes and propeller unsteady forces are carried out by CFD (Computational fluid dynamics) technology, and results are compared with the experimental data. The accuracy of the predicted noises depends on the CFD results. The predicted noises in model scale are then transformed to the full-scale values according to the pressure-similarity relation. It is found that propeller inflow is more uniform, and the radiating noise can be decreased.
Ship Seakeeping Performance Analysis
The motion of ships at sea is affected by waves from all directions. This results in complicated and irregular ship movement. The performance analysis of wave resistance can help us understand the movement and performance of a ship under the impact of wind and waves.
The wave resistance and behavior of a ship includes the operational performance of the instruments and equipment, as well as the work efficiency of the crew and job morale, all of which significantly influence proper task performance. Therefore, if an analysis of endurance and performance of a ship can be carried out at the initial design stage, design improvements and an assessment of safety can be made.
SOIC has several suitable tools for calculation and the movement analysis of different types of ship. These can be used to calculate the kinematic performance under various navigation conditions and provide prediction, analysis and recommendations for sea endurance and performance.
Ship Anti-rolling Stabilizer Fin Control System
The Ship Anti-rolling Stabilizer Fin System consists of a pair of active control fins and intelligent control cores mounted on both sides of the hull, which can automatically suppress the rolling moment caused by wind and waves and reduce the rolling motion of the ship in wind and waves, to improve comfort during the voyage.
In addition to the stability of the hardware system, this Control System analyzes the optimum control parameters based on the ship speed and sea conditions automatically by artificial intelligence in the design of core software, and combines the Anti-rolling Stabilizer Fin Control System with high-function and high-rigidity, and be capable of understanding the actual operation performance of stabilizer fin in all types of sea conditions by analyzing the log files of actual ship operations, for further calibration of the system to achieve the best performance.
(This product control system has applied for a patent with the Republic of China)
Analysis of Added Resistance in Waves
In this research, the numerical technique to predict added resistance in waves is developed. The added resistance in waves is considered as nonlinear interaction between hull and waves, and is difficult to be predicted correctly. In practice, to evaluate ship power in real seaway, an additional sea margin is introduced to take all uncertainties into account, such as added resistance in waves and propulsion efficiency in waves. However, to meet demands of ship energy efficiency, the conventional resistance evaluation, which using a rough margin to take over the added resistance prediction, would be challenged.
The main objective of this research is to establish the analysis technology of resistance performance for the ship sailing in waves; however, the added resistance in wind and waves is a highly non-linear problem, therefore, the degree of difficulty is rather high. Since it is highly recommended that the hull form design tool must be fast and reasonable during the early design stage, a hybrid approach is proposed, and validation in various hull types is carried out. The far-field method based on the Lin & Reed’s theory is adopted with velocity potentials obtained from linear two-dimensional strip theory. In addition, Fuji & Kuroda’s empirical formulation is adopted in the estimation of added resistance short waves. The works are done in various benchmarks, including a container vessel, an oil tanker, and a mono-hull fast ship to validate the proposed approach. By comparing with experimental data for various ship types, the accuracy of proposed hybrid approach is identified, and provides confidence to potential user.
Comparison of added resistance calculation and test value for each ship type in waves
Comparison of the peak added resistance for each ship type calculation and test value (average of speed for each ship