• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2018.11a
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• pp.241-247
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• 2018

Deep-sea fishing vessel No. 501 Oryong was fully flooded through its openings and sunk to the bottom of the sea due to the very rough sea weather on the way of evasion after a fishing operation in the Bearing Sea. As a result, many crew members died and/or were missing. In this study, a full-scale ship flooding and sinking simulation was conducted, and the sinking process was analyzed for the precise and scientific investigation of the sinking accident using a highly advanced Modeling & Simulation (M&S) system of the Fluid-Structure Interaction (FSI) analysis technique. To objectively secure the weather and sea states during the sinking accident in the Bering Sea, time-based wind and wave simulation at the region of the sinking accident was conducted and analyzed, and the weather and sea states were realized by simulating the irregular strong wave and wind spectrums. Simulation scenarios were developed and full-scale ship and fluid (air & seawater) modeling was performed for the flooding sinking simulation, by investigating the hull form, structural arrangement & weight distribution, and exterior inflow openings and interior flooding paths through its drawings, and by estimating the main tank capacities and their loading status. It was confirmed that the flooding and sinking accident was slightly different from a general capsize and sinking accident according to the simple loss of stability.

• International Journal of Fluid Machinery and Systems
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• v.6 no.2
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• pp.87-93
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• 2013

In order to study the effect of the fluid-structure interaction (FSI) on the simulation results, the external characteristics and internal flow features of a diffuser pump were analyzed with a two-way flow solid coupling method. And the static and dynamic structure analysis of the blade was also caculated with the FEA method. The steady flow field is based on Reynolds Averaged N-S equations with standard $k-{\varepsilon}$ turbulent model, the unsteady flow field is based on the large eddy simulation, and the structure response is based on elastic transient structural dynamic equation. The results showed that the effect of FSI on the head prediction based on CFD really exists. At the same radius, the van mises stress on the nodes closed shroud and hub was larger than other nodes. A large deformation region existed near inlet side at the middle of blades. The strength of impeller satisfied the strength requirement with static stress analysis based on the fourth strength theory. The dynamic stress varied periodically with the impeller rotating. It was also found that the fundamental frequency of the dynamic stress is the rotating frequency and its harmonic frequency. The frequency of maximum stress amplitude at node 1626 was 7 times of the rotating frequency. The frequency of maximum stress amplitude at node 2328 was 14 times of the rotating frequency. No matter strength failure or fatigue failure, the root of blades near shroud is the key region to analyse.

• Journal of the Society of Naval Architects of Korea
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• v.59 no.6
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• pp.393-399
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• 2022

During the ship hull design process, resistance performance estimation is generally calculated by simulation using computational fluid dynamics. Since such hull resistance performance simulation requires a lot of time and computation resources, the time taken for simulation is reduced by CPU clusters having more than tens of cores in order to complete the hull design within the required deadline of the ship owner. In this paper, we propose a method for estimating resistance performance of ship hull by simulation using a graph neural network. This method converts the 3D geometric information of the hull mesh and the physical quantity of the surface into a mathematical graph, and is implemented as a deep learning model that predicts the future simulation state from the input state. The method proposed in the resistance performance experiment of simple hull showed an average error of about 3.5 % throughout the simulation.

• Proceedings of the KSR Conference
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• 1998.11a
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• pp.137-143
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• 1998

Numerical simulation is conducted to clarify the heat transfer and fluid flow characteristics of traction motor for electric car SIMPLE algorithm based on finite volume method is used to make linear algebra equation. The governing equations are solved by TDMA(TriDiagonal Matrix Algorithm) with line-by-line method and block correction. From the results of simulation, the characteristics of cooling pattern is strongly affected by the size of hole in stator core. In the case of high rotational speed of rotor, temperature difference along the axial direction is more decreased than that of low rotational speed.

• Transactions of The Korea Fluid Power Systems Society
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• v.8 no.4
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• pp.24-31
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• 2011

Double-color Injection molding machine is the assembly of many kinds of mechanical, fluid power part and electric electronic control system. From in these, fluid power is a part where becomes the first core of this machine. Fluid power systems of double-color injection molding machine are modelled and analyzed using a commercial program AMESim. Partial system models which is divided according to functional operation are made and its analysis results shows how design parameters work on operational characteristics like pressure, flow rates, displacement at each node and so on. Analysis modeling and compared the data which gets from experiment and the analysis result which has a reliability got data. The results made by analysis will be used design of fluid power circuit for developing a double-color injection molding machine.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.6
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• pp.614-619
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• 2015

In this study, a dynamics model was developed to predict the motion performance of an Autonomous Underwater Vehicle (AUV). The dynamics model includes basic dynamic state variables of the hull and force terms to determine the motion of the AUV. The affecting terms for the forces are hydrostatic force, added mass, hydrodynamic damping, lift and drag forces. The force terms can be calculated using analytical and Computational Fluid Dynamics methods. For the underwater motion simulation, a simple PD controller was used. Also, the AUV was tested in a water tank and near sea for the partial verification of the fluid drag force coefficients and way-point tracking motions.

• Journal of Korea Foundry Society
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• v.35 no.2
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• pp.29-35
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• 2015

In this study, potential defects of ring-type cast products during the mold-filling stage of the casting process were investigated using computer simulation. The main focus was on the effects of runner extension and ingates. During the mold filling the molten metal flowed from the bottom to the top of the mold in two curved paths along the ring-type cavity. The fluid fronts in the two paths did not show the identical velocity during the mold filling stage. This difference in the filling speeds may cause defects such as voids and local contractions. The present model contained virtual fluid detectors at various positions inside the mold. When the molten metal passed those points, the volume of fluid jumped up from zero to one. The moments were measured to compare the speeds of the fluid fronts. We attempted various combinations of runner extensions and ingates to stabilize the flow and then to optimize the casting mold design.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.99-102
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• 2002

The present study describes a numerical analysis for simulation of the sloshing of flows with free-surface which contained in a rectangular tank The SOLA-VOF (Volume of fluid) method uses a fixed mesh for calculating the motion of flow and the free-surface. This Eulerian approach enables the VOF method to use only a small amount of computer memory for simulating sloshing problems with complicated free-surface contours. The VOF function, representing the volume fraction of a cell occupied by the fluid, is calculated for each cells, which gives the locating of the free-surface filling any some fraction of cells with fluid. Using SOLA-VOF method, the study describes visualization about simulation of the sloshing of flows and damping effect by baffle. Translation and pitching motion of the forms have been investigated The time-dependent changes of free-surface height are used for visualization subject to several conditions such as fluid height horizontal acceleration, sinusoidal motion, and viscosity. The free-surface heights were used for comparing wall-force, which is caused by sloshing of flows. Baffle was Installed to reduce the force on the wall by sloshing of flows. Damping effects was extensively expressed under the conditions such as baffle shape and position.

• International Journal of Fluid Machinery and Systems
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• v.7 no.3
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• pp.110-124
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• 2014

Surge phenomena in the zone of reduced speeds in a system of a nine-stage axial flow compressor coupled with ducts were studied analytically by use of a surge transient simulation code. Main results are as follows. (1) Expansion of apparently stable, non-surge working area of the pressure vs. flow field beyond the initial stage-stall line was predicted by the code in the lower speed region. The area proved analytically to be caused by significantly mismatched stage-working conditions, particularly with the front stages deep in the rotating stall branch of the characteristics, as was already known in situ and in steady-state calculations also. (2) Surge frequencies were found to increase for decreasing compressor speeds as far as the particular compressor system was concerned. (3) The tendency was found to be explained by a newly introduced volume-modified reduced surge frequency. It suggests that the surge frequency is related intimately with the process of emptying and filling of air into the delivery volume. (4) The upstream range of movement of the fluid mass having once passed through the compressor in surge was found to reduce toward the lower speeds, which could have caused additionally the increase in surge frequency. (5) The concept of the volume-modified reduced surge frequency was able to explain, though qualitatively at present, the behaviors of the area-pressure ratio parameter for the stall stagnation boundary proposed earlier by the author.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.10a
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• pp.313-320
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• 2002

A new semi-active control strategy for seismic response reduction using a neuro-controller and a magnetorheological (MR) fluid damper is proposed. The proposed control system consists of the improved neuro-controller and the bang-bang-type controller. The improved neuro-controller, which was developed by employing the training algorithm based on a cost function and the sensitivity evaluation algorithm replacing an emulator neural network, produces the desired active control force, and then the bang-bang-type controller causes the MR fluid damper to generate the desired control force, so long as this force is dissipative. In numerical simulation, a three-story building structure is semi-actively controlled by the trained neural network under the historical earthquake records. The simulation results show that the proposed semi-active neuro-control algorithm is quite effective to reduce seismic responses. In addition, the semi-active control system using MR fluid dampers has many attractive features, such as the bounded-input, bounded-output stability and small energy requirements. The results of this investigation, therefore, indicate that the proposed semi-active neuro-control strategy using MR fluid dampers could be effectively used for control of seismically excited structures.