16:00
Ship hydromechanics resistance VI
Chair: Jianqiang Wang
16:00
30 mins
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NUMERICAL STUDY OF TWO DIFFERENT TYPES OF SEMI-SUBMERSIBLE PLATFORMS WITH MOORING SYSTEMS IN THE SEA
Yao Peng, Decheng Wan
Abstract: With the increasing demand of floating structures in ocean, various types of platforms and mooring systems are designed to meet the need. And there is important significance for us to further understand how the platforms work with their mooring systems in different sea conditions. In this paper, motion responses of two different types of semi-submersible platforms with corresponding mooring systems are studied numerically by a viscous flow solver named naoe-FOAM-SJTU, which is developed from the open source toolbox OpenFOAM. A group of professors in our university have already conducted a series of model tests for our research objects, and the results of the presented numerical simulation are expected to compare with the model tests. Our studies are covered for different shapes, working conditions and mooring systems for each platform. We pay close attention to the motion responses of platforms and the forces in corresponding mooring lines. Several important conclusions are drawn.
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16:30
30 mins
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EXPERIMENTAL STUDY OF THE EFFECT OF SPRAY RAILS FOR AXE-BOW HIGH SPEED HULLS
Daehyuk Kim, Kye-pyo Rhee, Nakwan Kim, Jin-Hyung Ahn
Abstract: This paper presents experimental study of spray rails for axe-bow high speed hulls. Spray rails are generally used for the total resistance reduction. Spray rails are appended to most of high speed vessels to reduce spray generation. Some model tests for the investigation of spray rail effectiveness are conducted by Clement (1964a, 1964b) and Muller-Graf (1991). But used hull forms are planing hull and semi-displacement hull respectively, so the effectiveness of spray rails for other hull forms cannot be guaranteed. Hull form used in this paper is high speed axe-bow hull which are defined by Keuning (2001). In calm water tests, the resistance and running attitude (trim angle, rise of C.G.) are measured and spray generation change is evaluated from video capture. In motion in wave tests, pitch and heave motions are measured in head sea condition. Model tests are conducted by using high speed towing carriage and measurement system at Seoul National University. From the test results, is can be known that spray rails are very effective appendage to reduce the spray generation. The resistance and running attitude can be changed by the appended location of spray rails. Spray rails can change the running attitude, so pitch and heave motions in waves are also changed.
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17:00
30 mins
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MULTI-OBJECTIVE OPTIMIZATION FOR A SURFACE COMBATANT USING NEUMANN-MICHELL THEORY AND APPROXIMATION MODEL
Xiaoyi Liu, Jianwei Wu, Decheng Wan
Abstract: Hydrodynamic optimization of hull forms has drawn attention of both academia and industry during the development of shipbuilding industry and shipping business. An efficient potential flow theory based design optimization tool OPTShip-SJTU for ship hull form is presented in this paper, which is composed of three function modules: hull form deformation module, hydrodynamic performance prediction module and optimization module. Free-Form Deformation (FFD) method and Radial Basis Function (RBF) method are employed to modify the ship hull in global and local respectively. In order to reduce the cost of the optimization, which is always a challenging problem, a new hydrodynamic prediction tool based on Neumann-Michell (NM) theory and the approximation model is adopted. The high efficiency is illustrated by the application of OPTShip-SJTU to a surface combatant DTMB 5415. Wave resistance coefficients at three design speeds are minimized and a Pareto front of solutions is obtained. The optimal hulls are verified and analyzed by NM theory and a RANS-based CFD solver naoe-FOAM-SJTU. Numerical results confirm the availability and reliability of the OPTShip-SJTU.
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