• International Journal of Naval Architecture and Ocean Engineering
• /
• v.11 no.2
• /
• pp.736-749
• /
• 2019

This paper employs computational tools to investigate the diffraction effects in regular head waves on the added resistance and wake on the propeller plane. The objective ships are a 66,000 DWT bulk carrier and a 3,600 TEU container ship. Fixed and free to heave and pitch conditions at design speed have been taken into account. Two-phase unsteady Reynolds averaged Navier-Stokes equations have been solved using the finite volume method; and a realizable k-ε model has been applied for the turbulent closure. The free surface is obtained by solving a VOF equation. The computations are carried out at the same scale of the model tests. Grid and numerical wave damping zones are applied to remove unwanted wave reflection at the boundaries. The computational results are analyzed using the Fourier series. The added resistances in waves at the free condition are higher than those at the fixed condition, which are nearly constant for all wavelengths. The wake velocity in waves is higher than that in calm water, and is accelerated where the wave crest locates on the propeller plane. When the vertical motion at the stern goes upward, the wake velocity also accelerated.

• Journal of Sasang Constitutional Medicine
• /
• v.21 no.1
• /
• pp.44-52
• /
• 2009

1. Objectives Jeong-Jo's death has many mistery. So we understand rightly Jeong-Jo's death. we inspect closely medical records of 20 days before death(in The Annals of the Choson Dynasty(朝鮮王朝實錄), Hong Je Jun Se(弘齋全書)， GukSoBoGam(國朝寶鑑). We understand medical treatment before death. It is based on Jeong-Jo's Constitution. So we trace the cause of a Jeong-Jo's death rightly. 2. Methods According to The Annals of the Choson Dynasty(朝鮮王朝實錄), Hong Je Jun Se(弘齋全書) GukSoBoGam(國朝寶鑑). We found out Jeoung-Jo's Sasang constitutional elemet. We point on Jeoung-Jo's nature and emotion, temperament and talent, features and way of speaking, physical appearance, healthy state, ordinary symptom, pathological syndromes and pharmacology. so documentary records was worthy of notice. 3. Results and conclusions 1. Jeong-Jo has prominent cheekbones,flat face. It belong to Tae-eum. 2. Jeong-Jo's physical appearance is mild,around,large. It belong ro Tae-eum. 3. Jeong-Jo's favorite food and herb were belong to Tae-eum interior febrile disease herb. which is Exhale Dispersing Qi 4. So even though Jeoung-Jo is Tae-eum, He had a weak body. It main cause that Smoking, insomnia, heave work, Hwa disease. 5. Jeong-Jo's is Interior febrile disease induced form the liver affected by heat in Tae-eumin

• Journal of Ocean Engineering and Technology
• /
• v.26 no.6
• /
• pp.53-58
• /
• 2012

An experimental study on the hydrodynamic performance of a backward bent duct buoy (BBDB) was performed in a 2D wave tank. The BBDB is one of the promising oscillating water column (OWC) types of floating wave energy converters. Two different corner-shaped BBDBs (sharp-corner and round-corner) were used to measure the maximum chamber surface elevations and body motions for various incident wave conditions, and their hydrodynamic characteristics were compared. In order to investigate the effect of the pneumatic pressure inside the chamber, the heave and pitch angle interacted with elevations were compared for both open chamber and partially open chamber BBDBs. From the comparison study, the deviation in the chamber surface elevations between the two shapes of BBDBs was found to be significant near the resonance period, which may be explained by viscous energy loss. It was also found that the pneumatic pressure noticeably affected the chamber surface elevation and body motions.

• Journal of Navigation and Port Research
• /
• v.42 no.2
• /
• pp.127-136
• /
• 2018

The motion response of floating structures is of significant concern in marine engineering. Floating structures can be disturbed by waves, winds, and currents that create undesirable motions of the vessel, therefore causing challenges to its operation. For a floating structure, mooring lines are provided in order to maintain its position; these should also produce a restoring force when the vessel is displaced. Therefore, it is important to investigate the tension of mooring lines and the motion responses of a twin barge when moored to guarantee the safety of the barge during its operation. It is essential to precisely identify the characteristics of the motion responses of a moored barge under different loading conditions. In this study, the motion responses of a moored twin barge were measured in regular waves of seven different wave directions. The experiment was performed with regular waves with different wavelengths and wave directions in order to estimate the twin-barge motions and the tension of the mooring line. In addition, the motion components of roll, pitch, and heave are completely free. In contrast, the surge, sway, and yaw components are fixed. In the succeeding step, a time-domain analysis is carried out in order to obtain the responses of the structure when moored. As a result, the Response Amplitude Operator (RAO) motion value was estimated for different wave directions. The results of the experiment show that the motion components of the twin barge have a significant effect on the tension of the mooring lines.

• Journal of the Korean Institute of Gas
• /
• v.20 no.4
• /
• pp.1-6
• /
• 2016

A fuel supply system of heavy-duty CNG engine is composed as a module structure which is integrated by about 6 injectors. There are only one input and output passage for gas fuel supply in this injector module. The response performance for transient operation of an CNG engine is very poor because only one output fuel supply line is connected to the intake pipe after a throttle valve. In this study, a new guideline and internal flow design for the CNG injector module is suggested for the improvement of response performance by fluid dynamic simulations. As a result, the response performance of gas fuel supply can be improved by decreasing the total volume of internal flow passages and a same distance design from each injector to the exit of module shows good response performance and acquirement of linearity of fuel supply. But the injection order has little influence to injection performances.

• Ocean Systems Engineering
• /
• v.7 no.2
• /
• pp.121-141
• /
• 2017

The purpose of this paper is to understand and model the slow current (~2 m/s) effects on the global response of a floating offshore platform in waves. A time-domain numerical simulation of full wave-current-body interaction by a quadratic boundary element method (QBEM) is applied to compute the hydrodynamic loads and motions of a floating body under the combined influence of waves and current. The study is performed in the context of linearized potential flow theory that is sufficient in understanding the leading-order current effect on the body motion. The numerical simulations are validated by quantitative comparisons of the hydrodynamic coefficients with the WAMIT prediction for a truncated vertical circular cylinder in the absence of current. It is found from the simulation results that the presence of current leads to a loss of symmetry in flow dynamics for a tension-leg platform (TLP) with symmetric geometry, resulting in the coupling of the heave motion with the surge and pitch motions. Moreover, the presence of current largely affects the wave excitation force and moment as well as the motion of the platform while it has a negligible influence on the added mass and damping coefficients. It is also found that the current effect is strongly correlated with the wavelength but not frequency of the wave field. The global motion of a floating body in the presence of a slow current at relatively small encounter wave frequencies can be satisfactorily approximated by the response of the body in the absence of current at the intrinsic frequency corresponding to the same wavelength as in the presence of current. This finding has a significant implication in the model test of global motions of offshore structures in ocean waves and currents.

• Journal of the Korean Society for Railway
• /
• v.17 no.4
• /
• pp.233-244
• /
• 2014

In this study, an analysis method for maglev train-guideway interaction is verified using field measurement data. The cabin and bogies of the maglev train are modeled as rigid bodies that are allowed to have heave and pitch motions. Levitation forces from the electromagnetic suspensions on the bogies are controlled using an active control algorithm. The guideway is represented using the Euler-Bernoulli beam. Considering rigorously the changes in air-gaps and material points at which the levitation forces are applied due to the pitch motions of the bogies, dynamic analysis of maglev train-guideway interaction is performed. Using field measurement data, obtained from the Incheon Airport Maglev Railway, the analysis method is verified. Accuracy of the analysis method is investigated. It is determined that the structures in the railway are designed and constructed safely according to the design code for maglev railways.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.5 no.1
• /
• pp.161-177
• /
• 2013

High-speed vessels require good resistance and seakeeping performance for safe operations in rough seas. The resistance and seakeeping performance of high-speed vessels varies significantly depending on their hull forms. In this study, three planing hulls that have almost the same displacement and principal dimension are designed and the hydrodynamic characteristics of those hulls are estimated by high-speed model tests. All model ships are deep-V type planing hulls. The bows of no.2 and no.3 model ships are designed to be advantageous for wave-piercing in rough water. No.2 and no.3 model ships have concave and straight forebody cross-sections, respectively. And length-to-beam ratios of no.2 and no.3 models are larger than that of no.1 model. In calm water tests, running attitude and resistance of model ships are measured at various speeds. And motion tests in regular waves are performed to measure the heave and pitch motion responses of the model ships. The required power of no.1 (VPS) model is smallest, but its vertical motion amplitudes in waves are the largest. No.2 (VWC) model shows the smallest motion amplitudes in waves, but needs the greatest power at high speed. The resistance and seakeeping performance of no.3 (VWS) model ship are the middle of three model ships, respectively. And in regular waves, no.1 model ship experiences 'fly over' phenomena around its resonant frequency. Vertical accelerations at specific locations such as F.P., center of gravity of model ships are measured at their resonant frequency. It is necessary to measure accelerations by accelerometers or other devices in model tests for the accurate prediction of vertical accelerations in real ships.

• Journal of the Society of Naval Architects of Korea
• /
• v.55 no.3
• /
• pp.187-195
• /
• 2018

Ship's bottom slamming has been studied by many researchers for a very long time. But still some ships suffer structure damages caused by the bottom slamming impacts. This paper presents a practical computation method of the design impact pressure due to ship's bow bottom slamming. Large heave and pitch motions of a rigid hull ship are simulated by the nonlinear strip method in time domain and the relative colliding velocity between the bow bottom and the water surface is calculated using the simulated ship motions. The bottom slamming impact pressure is calculated as a product of the relative colliding velocity squared and the bottom slamming pressure coefficient that is obtained by modification of the SNAME pressure coefficients based on Ochi's slamming experiments. Not only the bottom slamming pressures but also the required bottom plate thicknesses are calculated and compared with those of the classification society rules. The comparisons show good agreements and it is confirmed that the present method is practically very useful for the bottom structure design against ship's bow bottom slamming impacts.

• Journal of the Korean GEO-environmental Society
• /
• v.11 no.12
• /
• pp.5-11
• /
• 2010

If the groundwater in rock joint is changed into ice, it induces the stress increment by volume increase. Also, if the ice is changed into groundwater again, the stress in joint decreases by volume decrease. The accumulated displacement and fatigues of joints are increased by the stress-hysterisis, induced from the continuous frost-thawing. Also the shear strength is decreased by them continuously. The stress-hysterisis is affected by the atmospheric temperature changes, whose behavior is visco-elasticity, usually. Therefore, Kelvin model could be used to analyze the frost-thawing behavior in winter. The measured data of total 5 points are examined, which are composed of 3 points of shallow joints and 2 points of deep joints. Because shallow weathered rocks have many joints, a lot of Kelvin model are connected and the behaviors are complicated. In case of deep joints, simple Kelvin model is applied and the behaviors are also simple.