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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Society of Naval Architects of Korea
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The Society of Naval Architects of Korea
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Volume & Issues
Volume 53, Issue 4 - Aug 2016
Volume 53, Issue 3 - Jun 2016
Volume 53, Issue 2 - Apr 2016
Volume 53, Issue 1 - Feb 2016
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Numerical Simulation of Flow around a Fixed Semi-submersible Offshore Structure Using the Modified Marker-density Method
Ha, Yoon-Jin ; Lee, Young-Gill ; Jeong, Kwang-Leol ; Yang, In-Jun ;
Journal of the Society of Naval Architects of Korea, volume 53, issue 1, 2016, Pages 1~9
DOI : 10.3744/SNAK.2016.53.1.1
It is important to research and understand the physical phenomenon around a semi-submersible offshore structure on waves and currents because the wave run-up and load occurs owing to the waves and currents. In this study, the numerical simulations are performed about flow around a fixed semi-submersible offshore structure. The Modified Marker-density method is adopted in the present computation procedure, this method is one of the various methods to define the free-surface. The present computation results are compared with existing experimental and numerical simulation(VOF method) results. And, the computation results are relatively coincident with the existing results of model test and numerical simulation by VOF method.
Modeling and Simulation of the 6 DOF Motion of a High Speed Planing Hull Running in Calm Sea
Yoon, Hyeon Kyu ; Kang, Namseon ;
Journal of the Society of Naval Architects of Korea, volume 53, issue 1, 2016, Pages 10~17
DOI : 10.3744/SNAK.2016.53.1.10
When a planing hull straightly runs and turns, its floating position and pitch angle are changed depending on its speed, and large transient motion happens. In this paper, six degrees of freedom(6 DOF) equations of motion, which could simulate the motion of a planing hull, are established. Static and dynamic forces in vertical plane are modeled using pre-calculated displacements and metacentric heights depending on various draft, lift under bottom, and vertical damping coefficients which are used to tune the final motion. Hydrodynamic coefficients in horizontal plane at various equilibrium state are calculated by using Lewandowski's empirical formula and the speed-dependent equilibrium state are calculated beforehand by Savitsky's formula. The speed effects are considered by curve-fitting the coefficients at various speed to the polynomials. Accelerating, decelerating and backing, turning, and zig-zag are simulated and compared with the sea trial results, and it is confirmed that the speed reduction, roll, and pitch during such maneuvers of sea trial and simulation are well consistent.
An Approach for Construction of Shipyard Simulation Environment based on Neutral File Format
Woo, Jong Hun ; Hwang, Yoon-Suk ; Nam, Jong-Ho ;
Journal of the Society of Naval Architects of Korea, volume 53, issue 1, 2016, Pages 18~28
DOI : 10.3744/SNAK.2016.53.1.18
In shipbuilding, the scheduling system is susceptible to sudden changes and thus it turns to be difficult to predict the differences between schedule and production records in advance. A computer-based simulation is commonly utilized to overcome the discrepancies occurred in estimating workloads and resulting processing times. The main drawback of this simulation-based solution is its limited applicability because, in most cases, each shipyard requires specific and customized simulation environment. By standardizing the planning data of the midterm scheduling system, as proposed in this paper, the efficiency of the current simulation model can be enhanced. To present an alternative approach, this paper begins with the analysis of the complex planning data structure of several shipyards and then proceeds to construct a standard data structure based on the neutral format. An interface application is developed for the data transaction and simulation in on-line environment. As a result, a simulation-based production management of shipyards can be achieved by the efficient prediction of planning and scheduling.
A Study of Piping Leadtime Forecast in Offshore Plant’s Outfittings Procurement Management
Ham, Dong Kyun ; Back, Myung Gi ; Park, Jung Goo ; Woo, Jong Hun ;
Journal of the Society of Naval Architects of Korea, volume 53, issue 1, 2016, Pages 29~36
DOI : 10.3744/SNAK.2016.53.1.29
In shipbuilding and offshore plant construction, pipe-stools of various types are installed. Moreover, these are many quantities but they must be installed in a successive manner. Due to these characteristics the pipe-stool installation processes easily tends to cause the schedule delays in the overall production processes. In order to reduce delay, the goal of this study is to predicts production’s lead time before manufacturing. Through this predictions it’s expected to reduce total production’s lead time by improving it's process. First of all, we made MLR(Multiple Linear Regression) and PLSR(Partial Least Square Regression) model to predict pipe-spool's lead time and then compared predictability of MLR and PLSR model. If a explanatory variable is added, it will be possible to predict results precisely.
Design of Asymmetric Pre-swirl Stator for LNG Carrier according to Variation of Stator Shapes
Lee, Choel-Min ; Shin, Yong-Jin ; Kim, Moon-Chan ; Choi, Jung-Eun ; Chun, Ho-Hwan ;
Journal of the Society of Naval Architects of Korea, volume 53, issue 1, 2016, Pages 37~44
DOI : 10.3744/SNAK.2016.53.1.37
Recently researchers are conducting a lot of research related to EEDI in order to satisfy IMO resolution MEPC. Especially they are interested in design of energy saving device. This paper is to design the asymmetric pre-swirl stator for 160K LNG carrier in order to reduce energy. Two types of the asymmetric pre-swirl stator are taken into account; constant and variable pitch angle stators. “constant” and “variable” mean state that the pitch of stators change by radius. The dimensions of the stators are initially determined using potential-flow code. The propulsion performances of the stators are predicted using viscous-flow code. The model test is carried out in towing tank in PNU. Prediction of ship performance generally follow ITTC recommended. Ship wake prediction was done by two method, ITTC 1978 and ITTC 1999. Therefore propulsion performances were compared ITTC 1978 with ITTC 1999 methods. Comparison components are delivered power and thrust deduction coefficient of the model. Final pre-swirl stator is selected by comparing experiment and CFD.
Numerical Investigation of the Impact Pressure Acting on Arbitrary Ship Sections Falling into the Water Surface
Boujnah, Salah ; Jung, Rho-Taek ;
Journal of the Society of Naval Architects of Korea, volume 53, issue 1, 2016, Pages 45~53
DOI : 10.3744/SNAK.2016.53.1.45
The interaction between the hull of ship and free surface of water generates important loads during slamming motion. In the present study, the slamming load applied on the sectional surface of two-dimensional arbitrary bodies has been investigated under several falling velocities. This simulation has been done with the commercial CFD software ANSYS FLUENT
. Through the conventional MARINTEK experiments for the benchmark of the simulation, we verified the impact pressure values between the experiments and simulation results. Two arbitrary ship bow section models, Panamax-like(with small convex bulb and flare) and Post panamax-like(with large convex bulb and flare) are also investigated. Simulation results show that a maximum impact pressure on the Post panama-like shape is higher than the Panamax-like shape. According to both a lump of water generated by arbitrary shape and various dead-rise angles of the shape, the pressure picks were enhanced in the simulation.
A Study on Design Constraints of a Supercavitating Underwater Vehicle
Kim, Seonhong ; Kim, Nakwan ;
Journal of the Society of Naval Architects of Korea, volume 53, issue 1, 2016, Pages 54~61
DOI : 10.3744/SNAK.2016.53.1.54
This paper defines the design constraint in consideration of the dynamic characteristics and stability in the longitudinal direction of a supercavitating vehicle. Available range of the design variables is calculated by numerical simulation and the cavity modeling of vehicle dynamics is performed first. Configuration parameters of the supercavitating vehicle to determine the vehicle dynamics and characteristics of the cavity are defined as design variables. Design constraints are supercavitation, trim velocity, stability and vehicle dynamics in transition phase. Numerical results show that in accordance with the change of the design variables, the proposed design constraints reflect the physical characteristics of the supercavitating vehicle. This research finds the design region where the constraints of supercavity and the trim velocity are satisfied, and the stability analysis refines the design results by excluding the region where the stability is not guaranteed. The stability analysis is particularly important for a vehicle with the short fin span.
A Study on Estimation of Added Resistance in Waves Using Modified Radiated Energy Method and Short Wave Correction Method
Oh, Seunghoon ; Yang, Jinho ;
Journal of the Society of Naval Architects of Korea, volume 53, issue 1, 2016, Pages 62~68
DOI : 10.3744/SNAK.2016.53.1.62
A simple calculation tool for added resistance in waves is developed to utilize for initial design or embedded module for navigation support system. In order to select an appropriate calculation method for added resistance in waves, three methods (drift method, integrated pressure method, radiated energy method) based on strip method are applied to Wigley I and KVLCC2. The methods for added resistance in waves give the underestimated results because it is difficult to consider nonlinear effects due to reflected wave. We apply asymptotic (Faltinsen's method) and empirical formula (NMRI's method) to improve the accuracy for short wave length region. In comparison with experimental results, the combination of radiated energy method and short wave correction method of NMRI is the most reasonable. However, a simple sum of results calculated by two methods gives rise to the overestimation of added resistance for short wave length region because added resistance of radiated energy method exits in total reflection region. To overcome this problem, modified radiated energy method is proposed using correction coefficient defined by reflection coefficient of NMRI's method. Finally, added resistance in regular waves is composed of added resistance of modified radiated energy method and that of short wave correction method of NMRI. Estimated added resistance in regular waves is validated by comparison with experimental results of other research groups.
Curved Hull Plate Forming based on SOAP Internet Services
Kim, Chan Suk ; Son, Seung Hyeok ; Shin, Jong Gye ; Lee, Philippe ;
Journal of the Society of Naval Architects of Korea, volume 53, issue 1, 2016, Pages 69~75
DOI : 10.3744/SNAK.2016.53.1.69
Fabrication of the hull plate demands a lot of man-hour and a high degree of technology. In recent years, commercial shipping orders have been fallen because of intensifying competition with low price of order and labor cost. In order to solve this problem, a countermeasure such as a cost reduction is required. In this study, we are dealing with the method of supplying the forming information of the hull to the production site. We reviewed studies of hull forming that have been proposed so far to develop a method for providing hull forming information. On the basis of given production plans from the production site of shipyard, we discuss how to convert shell plate to production plan. Then, we will discuss the efficiency of the distribution method through the network about the method of hull forming. Thus, we have modified the distribution method which was proposed before. Finally, we will introduce the enhanced method for providing fabrication information of the hull plate to the small and medium-sized shipyards.
A Study on the Maneuvering Hydrodynamic Derivatives Estimation Applied the Stern Shape of a Vessel
Yoon, Seung-Bae ; Kim, Dong-Young ; Kim, Sang-Hyun ;
Journal of the Society of Naval Architects of Korea, volume 53, issue 1, 2016, Pages 76~83
DOI : 10.3744/SNAK.2016.53.1.76
The various model tests are carried out to estimate and verify a ship performance in the design stage. But in view of the cost, the model test should be applied to every project vessel is very inefficient. Therefore, other methods of predicting the maneuverability with confined data are required at the initial design stage. The purpose of this study is to estimate the hydrodynamic derivatives by using the multiple regression analysis and PMM test data. The characteristics of the stern shape which has an important effect on the maneuverability are applied to the regression analysis in this study. The correlation analysis is performed to select the proper hull form coefficients and stern shape factors used as the variables in the regression analysis. The comparative analysis of estimate results and model test results is conducted on two ships to investigate the effectiveness of the maneuvering hydrodynamic derivatives estimation applied the stern shape. Through the present study, it is verified that the estimation using the stern shape factors as the variables are valid when the stern shape factors are located in the center of the database.