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Chiu F.-C.,National Taiwan University | Li W.-F.,National Taiwan University | Tiao W.-C.,China Corporation Register of Shipping
OCEANS 2014 - TAIPEI | Year: 2014

Rising fuel prices and regulations to reduce CO2 emission have become a strong driving force to push shipyards and ship owners to build and operate energy saving ships. To meet these increasing demands, many novel designs and devices have been developed for reducing drag or for improving propulsion efficiency of a ship in seaway. Furthermore, several approaches using passive or active oscillating fin to extract wave power to assist ship propulsion have also been explored. The objective of the present study is to investigate the feasibility of a concept using an active pitch-oscillating fin to harness wave power for propulsion enhancement of merchant ships. Experimental data of the NACA 0012 oscillating foil are adopted to validate the present CFD simulation. Dependence of propulsion performance on Reynolds number and submerged depth are investigated. It has been confirmed that thrust of a flapping fin increases but efficiency decreases with larger Reynolds number, and shallower submerged depth of fin has negative effect for propulsion. Through simulations, thrust and propulsion efficiency of a flapping fin equipped at bow in full-scale ship are assessed. An active pitch-oscillating fin together with heave motion driven by ship vertical response to waves may generate significant amount of thrust with relatively high efficiency. As an example shown in the paper, for a VLCC of 321 meter long, a bow fin with projected area to waterline area ratio of 1/143, pitching actively around its pivot axis, may save energy about 3.1%∼9.5% in the ship speed ranges of 12∼16.5 knot. © 2014 IEEE.

Lin T.Y.,National Taiwan University | Kouh J.S.,National Taiwan University | Wang P.W.,China Corporation Register of Shipping
Journal of Taiwan Society of Naval Architects and Marine Engineers | Year: 2013

The purpose of the seakeeping model test is to predict motion response which is important to estimate the safety and comfort indices in real sea operation. Although sea margin and waves and motions are closely related, a rough calculation of the former by empirical formula is typically sufficient. The goal of this paper is to test and demonstrate the capabilities of Reynolds-averaged Navier-Stokes equations (RANS) solver to evaluate added resistance in head waves with forward ship speed. The geometry of a real 1,700 TEU container ship was modeled. The bare hull resistance was first computed and verified with experimental data. To simulate regular waves, boundary conditions were set by the airy wave equation. Then the heave and pitch motions of the hull were simulated by applying the arbitrary Lagrangian-Eulerian (ALE) technique. The mean added resistance coefficients were carried out and applied to whole-year sea state statistics from the Taiwan Strait. Results showed that the motion responses were consistent with experiments while the sea margin of 20% was found to be overestimated than experimental prediction and potential theory but still lies within empirical estimation.

Quemener Y.,China Corporation Register of Shipping | Huang C.H.,China Corporation Register of Shipping
Collision and Grounding of Ships and Offshore Structures - Proceedings of the 6th International Conference on Collision and Grounding of Ships and Offshore Structures, ICCGS 2013 | Year: 2013

This study deals with the ship soft grounding mechanics applied to a Capsize bulk carrier. In this scenario, the ship runs aground by the bow on a smooth seabed. The grounding resistance capacity can be evaluated considering bow damage confined ahead of the collision bulkhead. The grounding capacity is characterized by the critical initial forward speed; if this speed is exceeded, the damage may propagate beyond the collision bulkhead when the ship comes to rest. This study proposes a mathematical model to analyze ship grounding and then validates the mathematical model predictions using a few ship grounding dynamic Finite Element Analyses (FEA). Results show that the predicted critical initial speed is significantly lower than the ship service speed. This study also presents a simplified formulation from the mathematical model to assess the critical initial speed. This formulation was used to evaluate the bow structural strengthening required to increase the ship grounding resistance capacity. © 2013 Taylor & Francis Group.

Quemener Y.,China Corporation Register of Shipping | Huang C.-H.,China Corporation Register of Shipping | Lee C.-F.,China Corporation Register of Shipping
Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE | Year: 2013

This study investigates the fracture failure of longitudinal members including cracks. Specifically, this study employs the failure assessment diagram methodology to assess the conditions of failure at the crack tip. Based on various crack configurations, this study establishes the analytical formulations of the crack-tip condition that are validated using finite element analyses. In addition, the material toughness is expressed in terms of crack-tip opening displacement. This study evaluates the failure stress of representative cracked members as a function of the crack length. This enables determining critical crack lengths corresponding to the maximum stresses derived from extreme loads. Finally, this study uses simplified fatigue crack growth analyses to characterize the critical crack length in terms of fatigue life. For members located in the deck and bottom regions, the critical crack lengths correspond to the end of the assessed fatigue life. Therefore, the fracture resistance of the longitudinal members is satisfactory as it will not cause the premature loss of the component. This study also provides analytical formulations for crack-tip conditions that could be employed in a reliability study linking fatigue crack growth and fracture under extreme loads. Copyright © 2013 by ASME.

Chen C.-C.,China Corporation Register of Shipping | Huang C.-H.,China Corporation Register of Shipping | Chen K.-C.,China Corporation Register of Shipping | Wang P.-W.,China Corporation Register of Shipping
Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE | Year: 2014

The International Association of Classification Societies (IACS) Harmonised Common Structural Rules (CSR-H) have been released and will take effect on July 1, 2015. The local loads under extreme motion conditions, defined in the CSR-H, were investigated for an oil tanker by using computational fluid dynamics (CFD) software, STAR-CCM+, and included bow flare slamming pressure and bottom slamming pressure at the bottom of the bow or stern bottom. The extreme motion defined in the CSR-H was investigated using the potential code HydroSTAR. To benchmark the numerical results, resistance and seakeeping model tests were performed on the oil tanker. The two test results were simulated using the two software packages, respectively, and the numerical results were in good agreement with the test results. Finally, this study demonstrated that the slamming pressures defined by the CSR-H are safe and conservative with regard to the structural design. Copyright © 2014 by ASME.

Quemener Y.,China Corporation Register of Shipping | Huang C.H.,China Corporation Register of Shipping | Chen K.C.,China Corporation Register of Shipping | Jhan Y.T.,China Corporation Register of Shipping
Journal of Taiwan Society of Naval Architects and Marine Engineers | Year: 2011

This study deals with the ship grounding mechanics applied to a bulk carrier. The ship with a forward speed runs aground by the bow on a shoal. In view of the bow crushing damage, a critical situation is met when the collision bulkhead in way of the keel starts being in contact with the seabed. Critical grounding scenarios are determined by a ship grounds on a seabed with a critical initial forward speed till rest while the structural damage does not exceed the critical situation. First, a mathematical model is proposed to analyze the ship grounding and extract the critical initial forward speed. The grounding process can be divided into two phases. The first phase represents the ship change of momentum, and the second phase is the bow sliding over the seabed. During those two phases, the kinetic energy of the ship is dissipated by friction with the seabed, bow structure plastic crushing and trim increase due to the lift of the bow. Then, the mathematical model is modified based on a few time-consuming ship grounding nonlinear FEAs. This modified mathematical model allows fast and versatile analyses of ship grounding. Finally, critical grounding scenarios including ship critical initial forward speed are estimated. The hull girder strength is also reviewed under critical scenarios. The results show that the hull girder strength is sufficient despite the lift of bow and the flooding caused by localized damages.

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