• International Journal of Naval Architecture and Ocean Engineering
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• v.2 no.2
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• pp.57-67
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• 2010

Experimental investigations were carried out on an Axi-symmetric Body Model fitted with Pump-jet Propulsor (PJP) in the Cavitation Tunnel at Naval Science and Technological Laboratory (NSTL). The tests were intended for evaluating the propulsion characteristics of the body and propulsor. The self propulsion point of the model for two configurations was determined after finding the corrections for tunnel blockage effects and differences in model length at zero trim. The results were found to match closely with the towing tank results. The rotor and stator torques also matched closely over full range of experiment. Further experiments were carried out on the body at $4.5^{\circ}$ angle of trim to investigate the propulsive performance and assess the operational difficulties in the sea. The results indicated an increase in resistance and decrease in rotor thrust; but the balance of torques between the rotor and stator was undisturbed, causing no concern to vehicle roll.

• The Journal of Korea Robotics Society
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• v.1 no.2
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• pp.203-211
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• 2006

In this research, a comprehensive study is performed upon the design of a quadruped walking robot. In advance, the walking posture and skeletal configuration of the vertebrate are analyzed to understand quadrupedal locomotion, and the roles of limbs during walking are investigated. From these, it is known that the forelimbs just play the role of supporting their body and help vault forward, while most of the propulsive force is generated by hind limbs. In addition, with the study of the stances on walking and energy efficiency, design criteria and control method for a quadruped walking robot are derived. The proposed controller, though it is simple, provides a useful framework for controlling a quadruped walking robot. In particular, introduciton of a new rhythmic pattern generator relieves the heavy computational burden because it does not need any computation on kinematics. Finally, the proposed method is validated via dynamic simulations and implementing in a quadruped walking robot, called AiDIN(Artificial Digitigrade for Natural Environment).

• Journal of the Society of Naval Architects of Korea
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• v.41 no.2
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• pp.90-97
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• 2004

Flow mechanism of contractive and dilative motion is numerically investigated to obtain a propulsive force in highly viscous fluid. An axisymmetric code is developed with unstructured grid system based on cell-centered scheme. It is validated by comparing with the results of Stokes approximation for the problem of uniform flow past a sphere in low Reynolds number(R$_{n}$=1). The validated code is applied to the simulation of contractive and dilative periodic motion of body whose results are quantitatively compared with the two dimensional case. In order to investigate the grid dependency, two different grids are applied to the present computations. The present study provides key information for the development of an axisymmetric Micro-hydro-robot.t.

• Journal of Ship and Ocean Technology
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• v.3 no.1
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• pp.1-11
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• 1999

Numerical simulation for the axisymmetric body with contractive and dilative periodic motion is carried out. The present analysis shows that a propulsive force can be obtained in highly viscous fluid by the contractive and dilative motion of axisymmetric body. An axisymmetric code is developed with unstructured grid system for the simulation of complicated motion and geometry. It is validated by comparing with the results of Stokes approximation with the problem of uniform flow past a sphere in low Reynolds number($R_n$ = 1). The validated code is applied to the simulation of contractive and dilative periodic motion of body whose results are quantitatively compared with the two dimensional case. The simulation is extended to the analysis of waving surface with projecting part for finding out the difference of hydrodynamics performance according to variation of waving surface configuration. The present study will be the basic research for the development of the propulsor of an axisymmetric micro-hydro-machine.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.105-110
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• 2010

Supersonic ejectors are simple mechanical components, which generally perform mixing and recompression of two fluid streams. Ejectors have found many applications in engineering. In aerospace engineering, they are used for high altitude testing (HAT) of a propulsion system by reducing the pressure of a test chamber. It is composed of three major sections: a vacuum test chamber, a propulsive nozzle, and a supersonic exhaust diffuser (SED). This paper aims at the improvement in HAT facility by focusing attention on the vertical firing rocket test stand with shock generators. Shock generators are mounted inside the SED for improving the pressure recovery. The results clearly showed that the performance of the ejector-diffuser system was improved with the addition of shock generators. The improvement comes in the form of reduction of the starting pressure ratio and the vertical height of test stand. It is also shown that shock generators are useful in reducing the total pressure loss in the SED.

• Bulletin of the Society of Naval Architects of Korea
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• v.25 no.1
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• pp.3-10
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• 1988

This paper presents some experimental investigations on the effectiveness of the Stern-End-Bulb(SEB) and the design procedure of the optimum one. Experimental method was discussed to search the optimum SEB and the resistance reduction rate was investigated from the resistance test results of the SEB series for a passenger boat and a container ship. The contribution of SEB on the propulsive coefficients was discussed from the self-propulsion test results for a container ship. It would be expected that the power saving rate is about 5.8 percents for a passenger boat and 3.6 percents for a container ship by optimum SEB, respectively.

• Journal of the Society of Naval Architects of Korea
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• v.40 no.2
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• pp.1-10
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• 2003

It is important to understand the flow characteristics such as wave and wake development around a ship for the design of the hull forms with better resistance and propulsive performance. The experimental results explicating the local flow characteristics are also invaluable for validation of the physical and numerical modeling of CFD codes, which are recently gaining acknowledgements as efficient tools for hull form evaluation This paper describes velocity and wave profiles measured in the towing tank for the KRISO 138K LNG Carrier (KLNG) model with propeller and rudder. The results contained in this paper can provide the valuable information on the effect of propeller and rudder on stern flow characteristics of the modern commercial hull form, furthermore, the present experimental data will provide important database for CFO validation.

• International Journal of Naval Architecture and Ocean Engineering
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• v.7 no.2
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• pp.390-398
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• 2015

Energy-saving devices for 317K VLCC have been developed from a propulsion standpoint. Two ESD candidates were designed via computational tools. The first device WAFon composes of flow-control fins adapted for the ship wake to reduce the loss of rotational energy. The other is WAFon-D, which is a WAFon with a duct to obtain additional thrust and to distribute the inflow velocity on the propeller plane uniform. After selecting the candidates from the computed results, the speed performances were validated with model-tests. The hydrodynamic characteristics of the ESDs may be found in improved hull and propulsive efficiencies through increased wake fraction.

• Bulletin of the Society of Naval Architects of Korea
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• v.19 no.4
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• pp.61-70
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• 1982

The hydrodynamic effects on resistance and propulsive performance were studied by using the data from model test and full scale speed trials. A series of model tests on 3 geosims for a 60,000 DWT Bulk Carrier was conducted at KIMM's Ship Experimental Towing Tank and the results analyzed by 1978 ITTC Performance Prediction Method show the correlation between 3 geosim models. Also powering data of full scale speed trials were analyzed by the newly developed computer program and the correlation analysis between ship and model was studied.

• Proceedings of the KIEE Conference
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• summer
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• pp.1343-1345
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• 2004

The inherent pulsating force generation makes the control of switched-reluctance motor quite complicate. So in this paper, an orthogonal scheme that can be applied to the control of LSRM will be presented. By using this scheme, the motor reluctance forces, which are magnetically decoupled and position dependent, can be projected onto sets of stationary axes that are aligned with the motor fixed secondary poles. Hence the electromagnetic forces can be controlled not only for driving the LSRM at its propulsive direction but also for alleviating the load at its normal direction. Simulation results will be provided to show the validity of the proposed scheme.