• Journal of Navigation and Port Research
• /
• v.31 no.10
• /
• pp.813-818
• /
• 2007

There are the C.W.C and Towing Tank to the model-test equipments of the boat. A model testing of the high speed boat have a difficult in the performance verification because of very a small the scale-ratio of the ship-model and restricted by flow-velocity of the C.W.C and X-carriage velocity of the T.T. In general, the stepped hull boat is a high of fuel-efficiency because of the resistance reduction by a small wetted surface-area in correspond without stepped-hull boat. But It have a tendency to be bad the rolling performance by reduced stern wetted-area In this paper, the high speed stepped planning-boats with & without attached a stern body were performed to compare the effect of resistance and rolling performance by using sea model-test method.

• Journal of Navigation and Port Research
• /
• v.32 no.8
• /
• pp.583-588
• /
• 2008

The planing craft is designed specifically to achieve comparatively high speed on the surface of the water. In general, the stepped hull craft has effect improvement in speed and fuel-efficiency because of the reduction of total resistance by a small wetted surface area without corresponding stepped hull craft. In this paper, the high speed stepped hull crafts with respect to the number of bottom steps were performed to compare the effect of resistance performance using at-sea model-test method. In conclusion, the stepped hull craft with twin-step was proved to be effective to reduce the total resistance.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.4 no.2
• /
• pp.162-171
• /
• 2012

A method of hydrodynamic discrete sources is applied for two-dimensional modeling of stepped planing surfaces. The water surface deformations, wetted hull lengths, and pressure distribution are calculated at given hull attitude and Froude number. Pressurized air cavities that improve hydrodynamic performance can also be modeled with the current method. Presented results include validation examples, parametric calculations of a single-step hull, effect of trim tabs, and performance of an infinite series of periodic stepped surfaces. It is shown that transverse steps can lead to higher lift-drag ratio, although at reduced lift capability, in comparison with a stepless hull. Performance of a multi-step configuration is sensitive to the wave pattern between hulls, which depends on Froude number and relative hull spacing.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2007.12a
• /
• pp.37-39
• /
• 2007

고속 활주형선의 선형시험 ${\cdot}$ 검증을 위하여 설 해상모형시험기법을 정립하였으며, 본 시험법을 이용하여 선미 보조동체 장착 유무에 따른 고속 Stepped Hull 선형의 횡동요 및 저항특성을 비교, 분석하였다.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.7 no.3
• /
• pp.500-508
• /
• 2015

High-speed heavy loaded monohull ships can benefit from application of drag-reducing air cavities under stepped hull bottoms. The subject of this paper is the steady hydrodynamic modeling of semi-planing air-cavity hulls. The current method is based on a linearized potential-flow theory for surface flows. The mathematical model description and parametric calculation results for a selected configuration with pressurized and open air cavities are presented.

• Journal of the Society of Naval Architects of Korea
• /
• v.42 no.4 s.142
• /
• pp.341-349
• /
• 2005

With increasing demands of high speed transportation, recently a lot of high speed marine vehicles, such as SWATH, semi-planing craft, planing craft, hydrofoil craft, SES and so on, have been paid attention especially in high speed region over the Froude number 0.5. The resistance characteristics of the vehicles should be experimentally evaluated in the towing tank. At the Seoul National University, a light-weight cantilever type towing carriage was devised and installed in the towing tank. Wireless measurement devices were also provided for appropriate data acquisition during high-speed towing tests. With the new carriage system, a series of model tests were performed to investigate the hydrodynamic characteristics of a stepped planning hull in the towing tank and the resistance performances of the hull are introduced in this report.

• Journal of Ocean Engineering and Technology
• /
• v.22 no.4
• /
• pp.84-89
• /
• 2008

It is hard to find experimental data for a model test of small high-speed planning boats. It is difficult to verify the performance seen in a model test for a high-speed boat because the ship-model scale-ratio is very small and the flow velocity of the circulating water channel and the X-carriage speed of the towing tank are restricted. Therefore most hull-form designs for high-speed small boats depend on the sea-trial test result for similar boats or evaluation through numerical calculations. This study investigated the anti-rolling effect of the stern sub-body in a 50-knot doss planning boat. To carry out this work, new model test procedures were set up in the actual sea. Using this method, the anti-rolling effect of the stern sub-body was investigated. A stern sub-body attached to a planning boat was proved to be effective in reducing the roll and pitch angle.

• Journal of Hydrospace Technology
• /
• v.2 no.2
• /
• pp.44-56
• /
• 1996

The effects of the air on the reductions in resistance when supplied under the bottom of a semi-planing ship with a step are investigated in the present study. A 1.275m long FRP model is constructed and the pressure and viscous tangential stresses over the planing surface of the hull with and without air supply are measured through measuring holes carefully selected at the towing tank of Seoul National University. Locations of holes most suitable for air injection are surveyed in front of the planing surface of the model with careful examinations of the limiting streamlines and pressure distributions measured without air supply. At those locations, found to be just front of the step, air has been supplied into a wake region to form an air filled cavity of fixed type. Flow rates and pressure of the supplied air as well as the local pressure and shear stress distributions on the hull surface are measured to understand the physics involved as well as to determine the conditions most effective in resistance reduction at the design speed. It has been found that total resistance of the stepped semi-planing hull can be considerably reduced if an air cavity generated by an adequate air injection at the bottom of the hull near the step. After the cavity optimized at the given speed, air bubbles also have been generated right behind the point where dividing streamlines re-attach to further reduce the frictional resistance but found to be not so effective as the air cavity in resistance reductions.