This research is targeted to apply the numerical method in the ship’s propeller design and analysis. In this paper, the Quasi Continuous Method developed based on lifting surface theory is applied to predict the performance of propeller in open water condition. This method allows the fast propeller prediction process and low computer cost required. In this research, the VLCC ship model and it propulsion system is preselected. The propeller of the VLCC ship is designed and analyzed using the propeller database system in the numerical software OCARI S-Power. Next, the function of Quasi Continuous Method in the software is applied to predict the open water performance of the designed propeller. Finally, the appropriate propeller model and it dimension is determined in this research. In conclusion, application of numerical software in propeller design is an advance solution where this solution is relatively high efficient compare to the traditional method.
This study compares the performance of a bearing with surface waviness liner to a plain bearing. Both bearings are functioned with palm oil as lubricant so that the potential advantages of the journal bearings could be identified. CFD analysis is developed to predict the numerical data for full film lubrication condition. A bearing of 60 mm in diameter with its ratio of length to diameter is 0.5, a clearance 250µm, and 200µm of wave amplitude is simulated. Semi circular wavy surface produces better results in term of load capacity than the plain journal bearing for a small eccentricity. The load carrying capacity is influenced by the increasing in speed of the shaft and the eccentricity ratio.
This study will highlight the motion characteristics of single body and multiple bodies of offshore structures due to the effect of hydrodynamic interaction by considering the gap distance, the presence of number of neighboring structures and the wave direction headings. In order to analyze the added mass, radiation damping and motion responses that are developed during the interaction between structures, commercial software ANSYS AQWA is used. The analysis are executed by using 100 m diameter of round-shaped FPSO as the reference point for a single body where it is compared with two bodies and three bodies by using 70 m diameter round-shaped FPSO and LNG vessel for gap distance of 25 m and 50 m and wave directions at 00, 450, 900, 1350 and 1800 headings. The results show same trend with previous studies and researches in which the motion responses due to the effect from other structures occur significantly on surge and pitch motions compare to heave motion though there are small interactions. As for overall, the gap distance between structures, the presence of number of neighboring structures and the wave directions affect the motions of multiple bodies of offshore structures due to hydrodynamic interaction.
Investigation about water entry problem is one of the basic methods for simulation of impacts due to “Slamming” on high-speed crafts. Those impacts can be considered as a main source for structural damages on hull, equipments and on top of that for crew and passengers. This subject has more importance for multi-hull crafts because their intermediate structure, which connects the main hulls, should have enough strength under the slamming loads and waves forces. For optimum design of structure and achieving the minimum weight as an important parameter of performance for high-speed crafts, the pressure distribution around this area and the impact velocity should be determined in various loading conditions. In current paper, numerical analysis of a typical section for Trimaran hull had done by ANSYS-CFX software for determination of peak pressures and followed by experimental tests for validation. The results of current research can be used as a way for determination of loads on structure of these types of vessels particularly in a basic design phase beside the guidelines, which has proposed, by the rules of classification societies.
