• Journal of Ship and Ocean Technology
• /
• v.8 no.4
• /
• pp.17-25
• /
• 2004

Hull girder stress monitoring system for container ship uses four long-base-strain-gages at mid-ship to monitor the resultant stresses and the applied moment components of horizontal, vertical and torsional moments. The bending moments are estimated by using the conventional strain-moment relations, however, the torsional moment related to the warping strain requires the assumption of the shape of torsional moments over the hull girder. Though this shape could be a sine function with an adequate period, it largely depends upon certain empirical formulas. This paper introduces additional four long-base-strain-gages at mid-ship to derive the longitudinal slope of the warping strain because this slope is directly related to the torsional moment by Bi-moment concept. An open-channel-type cantilever beam has been selected as a simplified model for container ship and the result has proved that the suggested concepts can estimate the torsional component accurately. Finally this method can become reliable technique to derive all external moments in hull girder stress monitoring system for container ships.

• Journal of the Society of Naval Architects of Korea
• /
• v.45 no.3
• /
• pp.337-343
• /
• 2008

There are various hull types on the mid-size superyachts around $30\;{\sim}\;45m$. In any case, it is important to design the proper hull shape in viewpoint of the reduction of wave resistance, because small vessels such as superyachts are running at relatively higher Froude Number than other merchant ships. FLUENT with a VOF option was employed to investigate the flow fields around the superyachts having three-typical hull types: U-, V-types and catamaran. Overall performances including free surface flow were compared to figure out hydrodynamic characteristics of superyachy by numerical simulation.

• Journal of Ocean Engineering and Technology
• /
• v.15 no.1
• /
• pp.1-6
• /
• 2001

This study focuses on the potential flow analysis for a hull with the transom stern. The method is based on a low order panel method. The Kelvin type free-surface boundary condition which is known to better fit experimental data for a high speed is applied. To treat a dry transom stern effect a special treatment for the free-surface boundary condition is adopted at the free-surface region after the transom stern. Trim and sinkage, which are important in high speed ships, are considered by an iterative method. Pressure and momentum approaches are used to calculate the wave resistance. Numerical calculations are performed for Athena hull and these results are compared with the experimental data and also other computational results.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.9 no.2
• /
• pp.92-97
• /
• 2006

Hull forms of a high speed small boat have been developed through numerical studies. A round bilge type hull form has been drived form a using chine hull form with HCAD, a hull form variation software. Wave resistance and the flow fields around the ships have been computed using well-known software, WAVIS. This software employs Rankine source method with non-linear tree surface condition as well as dry transom boundary conditions. The round bilge hull form showed better resistance performance than to the chine hull form for the whole speed range. However, considering the building and labor costs of the small shipyard, the chine hull form has been selected and its wave resistance characteristics has been improved by modifying the bow regions and applying the stem wedge. It is found that the effect of stem wedge is quite satisfactory to improve the resistance characteristics of high speed chine hull form.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.21 no.5
• /
• pp.552-557
• /
• 2015

A numerical simulation studies were performed to investigate a manoeuvring characteristics as function of stern hull form with the mathematical model. In order to consider the effect of the stern hull form and obtain the manoeuvring characteristics, a parameter($C_{wa}$) which is aft. water plane area coefficient is modified. Because modifying $C_{wa}$(${\pm}2%$) means that the stern hull form is modified to V-type or U-type, the numerical simulation was performed with this modified $C_{wa}$. A changing trend for the manoeuvring characteristics not only in deep water but also in shallow water such as directional stability, turning and zig-zag was investigated and presented as the results. Present study showed that the manoeuvrability in shallow water largely changed when the draught and water depth ratio(=d/H) become 0.5, and the stern hull form can affect to the manoeuvrability of a vessel navigating in restricted water depth. In addition, it showed that approaching the stern hull to U-type makes the advance and tactical diameter of turning motion large and the overshoot angle of zig-zag motions small. Otherwise, it showed approaching the stern hull form to V-type makes the advance and tactical diameter of turning motion small and the overshoot angle of zig-zag motions large in the present study.

• Journal of Ocean Engineering and Technology
• /
• v.17 no.2
• /
• pp.67-71
• /
• 2003

Using motions (Maruo) and wave reflection (the author), speed loss due to wind (van Berlekom) and ITTC standard spectrum, and various effects of weather(:such as weather intensity, ship type, ship size and draught) on ship speed performance at sea were investigated. Further, a comparison of the relative effects of weather and hull roughness on speed loss was also studied for a VLCC.

• Journal of the Society of Naval Architects of Korea
• /
• v.34 no.1
• /
• pp.87-92
• /
• 1997

This study was carried out to develop the initial hull form for G/T 89ton class fishing boat cooperatively with Korean Fishing Boat Association. 1be resistance performance of two basic hull forms of hard chine type and displacement type are compared experimentally.

• Structural Engineering and Mechanics
• /
• v.81 no.6
• /
• pp.781-790
• /
• 2022

The present paper describes a general procedure of the structural safety assessment for the independent type C tank of LNG bunkering ship. This strength assessment procedure consists of two main scheme, global Finite Element Analysis (FEA) model primarily for hull structure assessment and detailed LNG Tank structures FEA model including the cylindrical tank itself and saddle-support structures. Two kinds of mechanism are used, fixed and slides constraints in fore and rear of the saddle-support structures that result in a variation of the reaction forces. Finite Element (FE) analyses have been performed and verified by the strength acceptance criteria to evaluate the safety adequacy of yielding and buckling of the hull and supporting structures. The detail of FE model for an LNG type C tank and its saddle supports was made, which includes the structural members such as cylindrical tank shell, ring stiffeners, swash bulkhead, and saddle supports. Subsequently, the FE buckling analysis of the Type C tank has been performed under external pressure following International Gas Containment (IGC) code requirements. Meanwhile, the assessment is also performed for yielding and buckling strength evaluation of the cylindrical LNG tank according to the PD 5500 unfired fusion welded pressure vessels code. Finally, a complete procedure for assessing the structural strength of 500 CBM LNG cargo tank, saddle support and hull structures have been provided.

• Journal of the Society of Naval Architects of Korea
• /
• v.41 no.1
• /
• pp.15-22
• /
• 2004

Twin-skeg type stern shapes are recently adopted for very large commercial ships. However it is difficult to apply a CFD system to a hull form having twin-skeg, since grid topology around a twin-skeg type stern is more complicated than that of a conventional single-screw ship, or of an open-shaft type twin-screw ship with center-skeg. In the present study a surface mesh generator and a multi-block field grid generation program have been developed for twin-skeg type stern. Furthermore, multi-block flow solvers are utilized for potential and viscous flow analysis around a twin-skeg type stern The present computational system is applied to a 15,000TEU container ship with twin-skeg to prove the applicability. Wave profiles and wake distribution are calculated using the developed flow analysis tools and the results are compared with towing tank measurements.

• Journal of Ocean Engineering and Technology
• /
• v.13 no.2 s.32
• /
• pp.168-175
• /
• 1999

In the present paper, a hull form for the turtle boat type incinerating vessel was developed based on the Finite source Distribution Method(FDM) and 1-$C_p$ method. In order to obtain proper hull form within the limited time and budget, a computer program OCL(Optimization of $C_p$ and LCB) was developed adn used. For the confirmation of the theoretical results by OCL, these theoretical results were compared with results of model test in the circulating water channel (CWC)in Chosun University.