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

• Proceedings of the KSR Conference
• /
• 1999.05a
• /
• pp.60-66
• /
• 1999

Generally, bogie frame for EMU consists of side frame, crossbeam and transom. Among the main frame structure which has been produced in our company, crossbeam and transom have been made of circular shaped tube. In this un, welding process between circular crossbeam and circular transom is complicated and takes much time. To improve this problem, new rectangular tube shaped transom is adopted. In this paper, the processes and results of finite element analysis are described, which was carried out to evaluate the strength of new bogie frame according to UIC, JIS, KS code. FEA results show that the new bogie frame has sufficient static and fatigue strength. Comparing the FEA results with load test results should follow and further study for evaluating the fatigue strength will be pursued in future.

• 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 Ship and Ocean Technology
• /
• v.8 no.3
• /
• pp.8-17
• /
• 2004

A numerical method is developed for computing the free surface flows around a transom stern of a ship at a high Froude number. At high speed, the flow may be detached from the flat transom stern. In the limit of the high Froude number, the problem becomes a planning problem. In the present study, we make the finite-element computations for a transom stern flows around a wedge-shaped floating ship. The numerical method is based on the Hamilton's principle. The problem is formulated as an initial value problem with nonlinear free surface conditions. In the numerical procedures, the domain was discretized into a set of finite elements and the numerical quadrature was used for the functional equation. The time integrations of the nonlinear free surface condition are made iteratively at each time step. A set of large algebraic equations is solved by GMRES(Generalized Minimal RESidual, Saad and Schultz 1986) method which is proven very efficient. The computed results are compared with previous numerical results obtained by others.

• Journal of Ocean Engineering and Technology
• /
• v.20 no.3 s.70
• /
• pp.88-95
• /
• 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.

• Special Issue of the Society of Naval Architects of Korea
• /
• 2007.09a
• /
• pp.32-42
• /
• 2007

Container vessels are required to have a large KMT to load many containers which requires a wide transom stern form. The wide transom stern generates large stern waves particularly at the scantling draft. This means that reducing the stern wave leads to resistance reduction. Numerical analyses and Model tests for duck-tail of the stern part have been performed to reduce the resistance of the container vessel having the wide transom on the scantling draft and optimize the form of duck-tail with the change of the design parameter i.e. length and edge height. The optimized duck-tail increases the speed by 0.8 % at scantling draft.

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

• Bulletin of the Society of Naval Architects of Korea
• /
• v.8 no.1
• /
• pp.17-28
• /
• 1971

The coefficients of equations of heave, pitch and coupled motion are evaluated for the small typical fishing boat(KIST-MARK Fishing Boat) with transom stern in regular head sea. And the results of computations based on eight models of strip theory are compared one another for the forward speed Froude number 0.30. There are some distinctive differences among those theories for the hydrodynamic and coupling coefficients. The former seems to be caused by the effects of the transom stern and the latter of the foward speed.

• Journal of Navigation and Port Research
• /
• v.37 no.2
• /
• pp.137-142
• /
• 2013

The displacement Deep-V catamaran concept was developed in Newcastle University(UNEW) through development of the systematic Deep-V catamaran series. One of the most important Deep-V catamaran launched to date is Newcastle University's own multi-purpose research vessel, The Princess Royal. The vessel was launched in 2011 and enhanced the Deep-V catamaran concept further with the successful adoption of a novel anti-slamming bulbous bow and tunnel stern for improved efficiency. It was however identified that the vessel has substantial amount of dynamic trim that limited the visibility of the captain. The dynamic trim also increased the wave-making resistance thereby preventing the vessel from attaining its maximum speed in certain sea states. This paper therefore presents the application of devices such as Trim Tabs, Interceptors, Transom Wedges and Integrated Transom Wedges-Tabs to control the dynamic trim and improvement of fuel efficiency of the vessel. All of these energy saving devices were fitted into a model for tests in Newcastle University's Towing Tank. Model test verification confirmed that the optimum appendage was the interceptors, they produced a 5% power saving and 1.2 degree trim reduction at 15 knots, and investigations of full scale trials will be scheduled with and without application of device to compare the improvement of performance.

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