• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2010.10a
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• pp.46-47
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• 2010

추진기와 타가 놓여있는 선미부에서의 난류 유동에 의한 저항을 증가시키는 요인이 집중되어 있다. 트랜섬 선미를 가지고 있는 선박의 경우 선미선형에 의한 저항의 형태가 달라진다. $Re=2.8{\times}10^5$의 균일흐름에서, 선저와 트랜섬이 이루는 각도를 각각 $45^{\circ}$, $90^{\circ}$, $135^{\circ}$로 변형하여 선미선형을 선정하였으며, 자유 수면에서 모델의 하부까지의 깊이는 동일하게 적용하였다. 선저가 끝단에서 트랜섬 선미형상에 의해 급격한 각도를 이루는 지점에서 상하로 맥동하는 유동특성이 나타나며, 각도가 증가 할수록 와의 형태가 작아져 난류의 발생이 감소하였다.

• Journal of Navigation and Port Research
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• v.30 no.8 s.114
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• pp.631-636
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• 2006

In this paper, the wave pattern around the hull with the transom stern advancing on the free surface with a constant speed was taken into consideration. To solve the problem the numerical analysis program was developed using Rankine source panel method based on potential flow analysis technique. The non-linearity of the free surface boundary conditions was fully satisfied. To verify the validity of the developed program the numerical calculations for Athena hull and KCS(KRISO container ship) hull was performed. The results of the numerical computation was compared with the ones of the model test experiment.

• Journal of the Korean Society of Marine Environment & Safety
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• v.18 no.4
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• pp.352-359
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• 2012

An experiment was carried out to figure out the turbulence flow characteristics in the wake of the transom stern's 2-dimensional section by 2-frame grey level cross correlation PIV method at Re= $3.5{\times}10^3$, Re= $7.0{\times}10^3$. The angles of transom stern are $45^{\circ}$(Model "A"), $90^{\circ}$(Model "B") and $135^{\circ}$(Model "C") respectively. The depth of wetted surface is 40mm from free surface. Strong turbulence intensity appears at the interaction between the flow separation of the bottom of a model and the free surface. This study provides statistic flow information such as turbulence intensity, Reynolds stress and turbulence kinetic energy. Model C type (Raked transom) has low Reynolds stress and turbulence kinetic energy.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.29 no.1
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• pp.41-46
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• 2005

In this paper, the flow phenomena and free surface wave pattern around the hull with a transom stern advancing on the free surface in steady state had been studied and the numerical analysis program had been developed using Rankine source panel method based on potential flow analysis in which the non-linearities of the free surface boundary conditions had been fully satisfied. To verify the validity of the developed program the numerical calculations for Athena hull and KCS(KRISO container ship) hull had been performed and the results of the numerical computation had been compared with the ones of the model test experiment.

• Journal of Navigation and Port Research
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• v.35 no.10
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• pp.805-810
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• 2011

An experiment was carried out to figure out the instantaneous flow characteristics in the wake of the transom stern's 2-dimensional section by 2-frame grey level cross correlation PIV method at $Re=3.5{\times}103$, $Re=7.0{\times}103$. The stern angles of models were learning at $45^{\circ}$(Model "A"), $90^{\circ}$(Model "B") and $135^{\circ}$(Model "C") respectively based on the survey results of real ships. The depth of wetted surface is 40mm from free surface. As Reynolds number increases, vortices increase in volume and move their way to the downstream. Flow separation appeared at the end of model's bottom.

• Journal of Ocean Engineering and Technology
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• v.15 no.1
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• pp.1-6
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• 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 Ocean Engineering and Technology
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• v.20 no.3 s.70
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• pp.88-95
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• 2006

The resistance characteristics of a trimaran are studied, varying the bottom profile and transom stern of the main hull. The bottom profile is varied in three cases (convex, flat, concave). Using the experimental and numerical methods, the resistance performance of each hull form is compared. The experiments are carried out in ship model basin, and the numerical simulations are performed by a finite-difference method, based on the Marker and Cell scheme. Euler and continuity equationsare used for the governing equations of the flaw field around a trimaran with transom stern. The agreement of both results is good. The optimal bottom profiles for transom stern are presented for law-speed and high-speed regions, respectively.

• Journal of the Society of Naval Architects of Korea
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• v.42 no.4 s.142
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• pp.322-329
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• 2005

Viscous flows behind transom stern are analyzed based on CFD simulation results. Stern wave pattern is often complicated due to the abrupt change of stern surface curvature and flow separation at transom. When a ship advances at high speed, whole transom stern is exposed out of water, resulting in the so-called 'dry transom'. However, in the moderate speed regime, stern wave development in conjunction of flow separation makes unstable wavy surface partially covering transom surface, i.e., the so-called 'wetted transom'. Transom wave formation is usually affecting the resistance characteristics of a ship, since the pressure contribution on transom surface as well as the wave-making resistance is changed. Flow modeling for 'wetted transom' is difficult, while the 'dry transom modeling' is often applied for the high-speed vessels. In the present study CFD results from the RANS equation solver using a finite volume method with level-set treatment are utilized to assess the topology of transom flow pattern for a destroyer model (DTMB5415) and a container ship (KCS). It is found that transom flow patterns are quite different for the two ships, in conformity to the shape of submerged transom. Furthermore, the existence of free surface seems to after the flow topology in case of KCS.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.7
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• pp.1106-1115
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• 2021

In this study, a fin that controls ship stern flow was attached on stern hull of a 80k bulk carrier to improve resistance performance. The rectangular cross-sectional fin was attached at several locations on the hull, and angle to streamline was changed with constant length, breadth, and thickness. The resistance performance and wake on propeller plane of the hull with and without the fin were analyzed using model-scale computational fluid dynamics simulation. The analysis results were extrapolated to full-scale to compare the performance and wake of the full-scale ship. First, the fin changed path of bilge vortex that flowed into the propeller along the stern hull without the fin to transom stern. This change increased pressure of the stern hull and upper region of the propeller, so pressure resistance and total resistance of the hull were reduced - the nearer the fin location to after perpendicular (AP) and base line of the hull, the larger the reduction of the resistances. Second, nominal wake fraction of the hull with the fin was lower than that without the fin. This dif erence was in proportion to the angle of the fin, but the total resistance reduction was in proportion until a certain angle at which the reduction was maximum. The largest total resistance reduction was approximately 2.1% at 12.5% of length between perpendiculars from the AP, 10% of draft from the base line, and 14° with respect to the streamline.

• Journal of the Society of Naval Architects of Korea
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• v.45 no.1
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• pp.54-62
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• 2008

A new solution method was developed to solve the free surface flow around a hull and named as 'Variable Free Surface Panel Method'. In the method the non-linearity of the free surface boundary conditions was fully taken into account and the raised panel method was employed to effectively solve the problem. The transom stern flow was also considered and the panel on the hull was generated using the panel cutting method. Numerical calculations were performed for KCS(KRISO Container Ship) hull form and compared with the experimental data to confirm the validity of the method. The comparison with the conventional free surface panel method was also accomplished. It is confirmed that new method gives more reliable results than the conventional method.