• Journal of the Korean Society of Marine Environment & Safety
• /
• v.22 no.6
• /
• pp.615-624
• /
• 2016

In this study, two rectangular barges in close proximity were simulated to analyze the characteristics of motion responses due to hydrodynamic interactions. Using a numerical solution from DNV-GL SESAM, coupled stiffness matrix terms for these same FEM models were added to the multiple body modes in the surge direction. Potential theory was used to calculate the first order radiation and diffraction effects on the simulated barge models. In the results, the sheltering effect of the barges was not shown at 1.3 rad/s with hull separation of 20 m in transverse waves. The separation effect between the barges was more clear with longitudinal waves and a shallow water depth. However, sway forces were influenced by hull separation with transverse waves. The peaks for sway and heave motion and sway force occurred at higher frequencies as hull separation narrowed with longitudinal and transverse waves. Given a depth of 10 m, the sway motion on the lee side of a coupled barge made a significant difference in the range of 0.2-0.8 rad/s with transverse and oblique waves. Also, the peaks for sway force were situated at lower frequencies, even when incident waves changed.

• Journal of computational fluids engineering
• /
• v.1 no.1
• /
• pp.55-63
• /
• 1996

Numerical computations are carried out to analyze the characteristics of flow fields around Air Supported Ships. The computations are performed in a rectangular grid system based on MAC(Marker And Cell) method. The governing equations are represented in finite difference forms by forward differencing in time and centered differencing in space except for its convection terms. For the certification of this numerical analysis method, the computations of flow fields around a Catamaran, an ACV(Air Cushion Vehicle) modeled with pressure distribution on free surface and two SES(Surface Effect Ship)'s are carried out, The results of the present computations are compared with the previously presented computational and experimental results in the same condition.

• Journal of the Korea Computer Graphics Society
• /
• v.24 no.2
• /
• pp.11-20
• /
• 2018

We propose a new method particle-based method that explicitly preserves thin liquid sheets for animating liquids on CPU-GPU heterogeneous computing framework. Our primary contribution is a particle-based framework that splits at thin points and collapses at dense points to prevent the breakup of liquid on GPU. In contrast to existing surface tracking methods, the our method does not suffer from numerical diffusion or tangles, and robustly handles topology changes on CPU-GPU framework. The thin features are detected by examining stretches of distributions of neighboring particles by performing PCA(Principle component analysis), which is used to reconstruct thin surfaces with anisotropic kernels. The efficiency of the candidate position extraction process to calculate the position of the fluid particle was rapidly improved based on the CPU-GPU heterogeneous computing techniques. Proposed algorithm is intuitively implemented, easy to parallelize and capable of producing quickly detailed thin liquid animations.

• Journal of Navigation and Port Research
• /
• v.31 no.8
• /
• pp.683-687
• /
• 2007

Hydroelastic deformation of pontoon type floating structure in waves is critical in structural design. Therefore, it is necessary to develop additional technology that make to dissipate the wave energy as the submerged horizontal plate. In this study, we investigate the characteristics of hydrodynamic interaction effect by the submerged plate affecting to the radiation forces on a pontoon type floating structure using numerical analysis. We have developed the numerical method based on the composite grid system that consists of moving and fixed grid to compute the radiation forces due to the heaving motion of pontoon type floating structure and submerged plate. The numerical simulations based on the finite difference method are carried out to solve the fully nonlinear free surface involving the breaking waves and compared with the experimental data to confirm the reliability of the numerical method. Then, we discuss the interaction effects on the hydrodynamic forces that could influence on the hydroelastic response of floating structure.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.17 no.5
• /
• pp.1160-1167
• /
• 2013

Web based simulation service is utilized to computationally analyze various phenomena in real world according to the progress of network and computing technology. In this paper, we present an improvement and utilization of e-AIRS (e-Science Aerospace Integrated Research System). e-AIRS, has been utilized to support web based CFD simulation service since 2008. has some problems such as stable system, pre processing, post processing. To solver this problem, we improved e-AIRS such as distributed service processing, personal simulation job assignment control, and faster data loading. After improvement, although users increase from 110 to 606, the priority of user requirements is changed from stable system to pre/post processor. User requirements and statistics about e-AIRS simulation service for each semester is analyzed to support more stable and comfortable service.

• 한국전산유체공학회:학술대회논문집
• /
• 2001.05a
• /
• pp.85-92
• /
• 2001

중력이 작용하는 압축성유체를 고려함에 있어, 밀도성층 뿐만 아니라 엔트로피 성층의 고려도 중요하다. 본 연구에서 압축성격자볼츠만 유체모델을 이용한 차분계산법을 이용하여 2차원 채널에서 성층류의 전형적인 형상인 선택취수현상을 시뮬레이션 하였으며, 본 모델의 유효성을 확인하였다. 또한 비점성, 비압축성유체의 선택취수흐름과의 차이에 관해서 압축성의 관점에서 고찰하였다.

• Journal of the Society of Naval Architects of Korea
• /
• v.28 no.2
• /
• pp.118-131
• /
• 1991

The effects of free surface on vortex shedding phenomena around a bluff body were studied by both numerical simulation and flow visualization experiments. A vortex method, which approximates the vorticity field as the sum of discrete vortices; was used for the numerical simulation. Flow visualization experiments were performed in the KRISO cavitation tunnel. Hydrogen bubble was used as illumination material. Free surface elevation was also measured during experiments. The hydrodynamic drag and lift were predicted by numerical simulation. The predicted period of vortex shedding was compared with the results of experiments.

• Journal of Navigation and Port Research
• /
• v.32 no.8
• /
• pp.603-609
• /
• 2008

Manta-type Unmanned Undersea Test Vehicle(MUUTV) is based on the same design concept as Unmanned Undersea Vehicle called Manta Test Vehicle(MTV), which was originally built and operated by the Naval Undersea Warfare Center(Lisiewicz et al., 2000, Sirmalis et al. 2001). The authors carried out the sensitivity analysis of the response of manoeuvring motion of MUUTV to changes in hydrodynamic derivatives, In order to calculate the sensitivity indices of hydrodynamic derivatives on MUUTV, the method by Sen(2000) was adopted Basically the dynamic mathematical model with six degrees of freedom by Feldman(1979) is used but a little revised, refered to Sohn et al.(2006) and some experiment in circulating water channel. Through the present research, some hydrodynamic derivatives of significance are found out, and also the numerical simulation using simplified mathematical model based on result of sensitivity analysis is ascertained to be enough for prediction of manoeuvring characteristics of MUUTV.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.34 no.2
• /
• pp.129-136
• /
• 2010

Axial piston pumps have been widely used as power sources for hydraulic systems, but studies on the fluid flow within the pump have been usually performed using 1-D analysis because of the difficulties in considering the fluid compressibility, high-speed revolution, variation of the flow rate, and complicated geometry. The goal of this study was to understand the hydraulic fluid flow within axial piston pumps by using the 3-D numerical method and the process of generating discharge pressure ripples. To improve the convergence and robustness of the simulation model, a grid system was constructed with hexahedron-type grids around the valve plate. Furthermore, we employed an empirical formula to describe the relationship between the oil density and pressure. The CFD (computational fluid dynamics) results compared well with the experimental data.

• Journal of Korea Society of Industrial Information Systems
• /
• v.29 no.1
• /
• pp.117-123
• /
• 2024

Bubbles generated in water receive an upward buoyant force due to the density and pressure difference of the surrounding fluid. Additionally, the behavior, shape, and heat exchange process of bubbles vary depending on the viscosity, surface tension, rising speed, and size difference with the surrounding fluid. In this study, we modeled speed, and heat transfer of a high-temperature single bubble rising in a cylindrical water tank. For this purpose, velocity, and temperature of the bubbles were calculated using theoretical equations, to be compared with numerical simulation results. The numerical analysis was performed using a commercial software, and the stability of the numerical analysis with mesh size was confirmed through calculation of the grid convergence index. The numerical analysis of the rising speed and temperature of a single bubble showed the values to converge when the minimum cell size was 1/160 of the bubble diameter, and the temperature decrease was confirmed to be the same as that of the surrounding fluid within 0.05 seconds.