• 한국소음진동공학회논문집
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• 제21권7호
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• pp.643-649
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• 2011

This work presents an active vibration control of a stiffened hull structure using a flexible macro fiber composite(MFC) actuator. As first step, the governing equation of the hull structure is derived in a matrix form and its dynamic characteristics such as natural frequency are obtained via a finite element analysis(FEA). The natural frequencies obtained from the FEA are compared with those determined from experimental measurement. After formulating the control model in a state space representation, an optimal controller is designed in order to attenuate the vibration of the stiffened hull structure. The controller is then empirically realized through dSPACE and control responses are evaluated in time domain.

• 대한조선학회논문집
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• 제42권5호
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• pp.506-515
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• 2005

Novel ships are commonly required iterative hull form modifications until she get reputation for new marine environment. Small FRP boats are manufactured in a identical shape with a mould. It implies that every modification step requires great time and expense which makes it difficult to improve the hull form promptly. Domestic hull form of small fishing boat of force has been evolved from the traditional hull form of developable shape. Utilizing this typical developable characteristics of small boats, ,New mouldless production method for FRP boat has been suggested and it is confirmed that the method is recommendable for a petty order of hull in evolving period of hull form development.

• International Journal of Naval Architecture and Ocean Engineering
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• 제12권1호
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• pp.723-732
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• 2020

A theoretical calculation model for ship stern bearings with large hull deformation is established and validated theoretically and experimentally. A hull simulation model is established to calculate hull deformations corresponding to the reaction force of stern bearings under multi-factor and multi-operating conditions. The results show that in the condition of wave load, hull deformation shows randomness; the aft stern tube bearing load obeys the Gaussian distribution and its value increases significantly compared with the load under static, and the probability of aft stern tube bearing load greater than 1 is 65.7%. The influence laws and levels between hull deformation and bearing reaction force are revealed, and suggestions for ship stern bearing specifications are proffered accordingly.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문초록집
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• pp.348.1-348
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• 2002

This paper deals with the vibration reduction of the hull mount system of ship structures brought by ER smart structures. The hull mount is used to isolate the vibration form the immersed structures. Utilizing the tunable characteristics of ER fluids, ER insert are made In the hull mountint structure. Different types of ER inserts are proposed and the vibration characteristics are investigated. (omitted)

• 한국항해학회지
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• 제12권3호
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• pp.23-37
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• 1988

This paper deals with the method of determining the drag of hull surface which has any quality of roughness. The method consists mainly of the theoretical point of view, then the theory enables the drag coefficient to be calculated at full scale. The hydrodynamical roughness function of hull surface ${\triangle}U_+$, affected by the hull roughness are considered as to two cases, smooth surface and rough surface case separately. The inadequacy of a single parameter to define hull roughness is discussed and thus an as additional texture parameter is proposed.

• 한국항해학회지
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• 제21권2호
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• pp.41-46
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• 1997

In this paper, important parameters of fast catamaran hull form are investigated. Praticularly, length-displacement ratio, demihull spacing, trim and hull form on resistance performance are analyzed. Also, the usefulness of SHIPFLOW program for hull form development is studied. The computed results by using SHIPFLOW program are compared with experimental results in model test.

• 대한조선학회지
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• 제22권2호
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• pp.35-48
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• 1985

The present work develops a method of evaluating thrust deduction and wake for different loads of the propeller using the concerted application of the theoretical tools and experimental techniques. It also shows the applicability of the new method to the design of optimum hull form. Firstly, the problem of hull-propeller interaction was analyzed in terms of inviscid as well as viscous components of the thrust deduction and wake. The wavemaking resistance of a hull and propeller were mathematically represented by sources on the hull surface and sink on the propeller plane, respectively. The strength of sink was determined by utilizing the radial distributions of propeller load and nominal wake. The resistance increment due to a propeller and the axial perturbation flow induced by the hull in the propeller plane were calculated. Especially, the inviscid component of the thrust deduction was calculated by subtraction the wavemaking resistance of a bare hull, the wavemaking resistance of a free-running propeller and the augmentation of propeller resistance due to hull action from the wavemaking resistance of the hull with a propeller. The viscous components of the thrust deduction and wake were estimated as functions of propeller load which were established by the propeller load varying test after deduction the calculated inviscid components. Secondly, an analysis method of powering performance was developed based on the potential theory and the propeller load varying test. The hybrid method estimates the thrust deduction, wake and propeller open-water efficiency for different propeller load. This method can be utilized in the analysis of powering performance for the propeller load variation such as the added resistance due to hull surface roughness, the added resistance due to wind, etc. Finally, the hybrid method was applied to the optimum design of hull form. A series of afterbody shapes was obtained by systematically varying the waterplane and section shapes of a parent afterbody without changing the principal dimensions, block coefficient and prismatic coefficient. From the comparison of the predicted results such as wavemaking resistance, thrust deduction, wake and delivered power, an optimum hull form was obtained. The delivered power of the optimized hull form was reduced by 5.7% which was confirmed by model tests. Also the predicted delivered power by the hybrid method shows fairly good agreement with the test result. It is therefore considered that the new analysis method of powering performance can be utilized as a practical tool for the design of optimum hull form as for the analysis of powering performance for the propeller load variation in the preliminary design stage.

• Journal of Biosystems Engineering
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• 제20권3호
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• pp.250-261
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• 1995

This study has been performed to develop an agricultural waste incinerator to combust the rice hull originated from RPC with the typical disposal treatment capacity of 30kg/h and to test performance of the developed incinerator. Experimental results are summarized as following. 1. The optimum feed rate of rice hull of the incinerator is 30kg/h with air ratio of 1.5. 2. The contents of $SO_2$ in flue gas is maximum 18ppm(when rice hull feed rate was 20kg/h and air ratio of 1.5), minimum 7ppm(when rice hull feed rate was 30kg/h and air ratio of 1.5) and average 11ppm. So there is no environmental pollution problem for the incinerating treatment of rice hull of the RPC. 3. The temperature of water of heat exchanger are $53^{circ} C$ and $62^{circ} C$ with water flow rate $3{ell}/min$ and $1.5{ell}/min$ at the optimum combustion condition, respectively. 4. According to theoretical energy calculation, the energy from rice hull combustion may be amounted as much as 80%~190% of energy supplied by kerosene required by RPC.

• International Journal of Naval Architecture and Ocean Engineering
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• 제5권4호
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• pp.502-512
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• 2013

Simulations of cavitation flow and hull pressure fluctuation for a marine propeller operating behind a hull using the unsteady Reynolds-Averaged Navier-Stokes equations (RANS) are presented. A full hull body submerged under the free surface is modeled in the computational domain to simulate directly the wake field of the ship at the propeller plane. Simulations are performed in design and ballast draught conditions to study the effect of cavitation number. And two propellers with slightly different geometry are simulated to validate the detectability of the numerical simulation. All simulations are performed using a commercial CFD software FLUENT. Cavitation patterns of the simulations show good agreement with the experimental results carried out in Samsung CAvitation Tunnel (SCAT). The simulation results for the hull pressure fluctuation induced by a propeller are also compared with the experimental results showing good agreement in the tendency and amplitude, especially, for the first blade frequency.

• 대한조선학회논문집
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• 제50권3호
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• pp.129-137
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• 2013

Each owner or operator of offshore products uses a maintenance management system like CMMS(Computerized Maintenance Management System) in order to manage their assets effectively and efficiently for a long time. But most of maintenance management systems have been focused on machinery items, not on 'Hull' until now. On the other hand, classifications like ABS, DNV, GL are having a sale on hull inspection and maintenance system for ships and an interest in hull maintenance system is increasing because of the application of EDD(Extended Dry Docking). This paper discusses the concept, inspection process and the practical application of Hull maintenance for Semi-submersible drilling rig to extend the service life and run a stable operation.