• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.568-571
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• 2008

The computation of moving interface by the level set method typically requires reinitializations of level set function. An inaccurate estimation of level set function ${\phi}$ results in incorrect free-surface capturing and thus errors such as mass gain/loss. Therefore, accurate and robust reinitialization process is essential to the free-surface flows. In the present paper, we pursue further development of the reinitialization process, which evaluates directly level set function ${\phi}$ using a normal vector in the interface without solving the re-distancing equation of hyperbolic type. The Taylor-Galerkin approximation and P1P1splitting FEM are adopted to discretize advection equation of the level set function and the Navier-Stokes equation, respectively. Advection equation of free surface and re-initialization process are validated with benchmark problems, i.e., a broken dam flow and time-reversed single vortex flow. The simulation results are in good agreement with the existing results.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.10
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• pp.754-760
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• 2008

Computation of moving interface by the level set method typically requires the reinitialization of level set function. An inaccurate estimation of level set function $\phi$ results in incorrect free-surface capturing and thus errors such as mass gain/loss. Therefore, an accurate and robust reinitialization process is essential to the simulation of free-surface flows. In the present paper, we pursue further development of the reinitialization process, which evaluates level set function directly using a normal vector on the interface without solving there-distancing equation of hyperbolic type. The Taylor-Galerkin approximation and P1P1 splitting/SUPG (Streamline Upwind Petrov-Galerkin) FEM are adopted to discretize advection equation of the level set function and the incompressible Navier-Stokes equation, respectively. Advection equation and re-initialization process of free surface capturing are validated with benchmark problems, i.e., a broken dam flow and timereversed single vortex flow. The simulation results are in good agreement with the existing results.

• Journal of Korean Society of Steel Construction
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• v.26 no.5
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• pp.485-498
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• 2014

In this paper, vehicle-bridge interaction analysis under a series of moving vehicles to simulate a lane load was performed to estimate impact factor of the main cable, hanger and girder for the selected suspension bridges with 404m and 1545m main span. Korea Bridge Design Code(Limit State Design) was selected for the live model in which KL-510 truck was modeled 6-d.o.f. vehicle and a lane load was simulated by a series of single-axle vehicles. For the 404m main span bridge, hinge-type and floating-type girders at the tower were considered to examine the impact factor according to the connection and supporting type of the girders. The parameters considered herein are the types of live load-a truck only and a truck plus lane load, eccentricity of moving vehicles, road surface roughness and vehicle speed. The road surface roughness was randomly generated based on ISO 8608 and it was applied to the truck only. The impact factors were also evaluated by using the influence line method that is commonly used in cable-supported bridges and compared with those from vehicle-bridge interaction analysis.

• Journal of Ocean Engineering and Technology
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• v.24 no.5
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• pp.31-38
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• 2010

The Floating storage and re-gasification unit (FSRU), which has large cargo storage tanks, is a floating liquefied natural gas (LNG) import terminal. The sloshing motion in tanks that are partially filled with LNG can cause impact pressure on the containment system and affect the global motion of the FSRU. Therefore, the accurate prediction of sloshing motion has been a significant issue in the offshore gas production industry. In this paper, a particle method based on the moving particle semi-implicit (MPS) method proposed by Koshizuka and Oka (1996) has been modified to predict sloshing motion accurately in a rectangular tank with the filling ratio of water. The simulation results, including the violent sloshing of the fluid, were validated by comparison with the original MPS method.

• Journal of Fashion Business
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• v.17 no.1
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• pp.170-185
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• 2013

The suitability of the pattern manufactured with the development figure was considered by reviewing the development conditions that can be directly connected to the basic pattern in the human body surface development figure with the cast bandage method. The method to prepare the sleeve basic pattern was based on the cylindrical surface development method, and the sleeve basic pattern covering the 45 and 90 degrees momentum of the arm-movement was made by using the cast-type body surface development figure prepared with the horizontal line of the sleeve hem placed horizontally in the plan and by combining the cast-type body surface development figure in the standing position with the figure in the moving position. The test clothing was prepared with the sleeve pattern adding the bodice pattern in the standing position and the momentum and was worn on the FRP replica. The relationship theory of the body surface development figure with the pattern was derived by reviewing the suitability from the wearing state. The sleeve-cap height of the sleeve basic pattern resulted in about 80% in the standing position when the needs for a physical activity are 45 degrees and the about 50% when the needs for a physical activity are 90 degrees. The additional size of the diagonal length of the sleeve-cap could be set as "0" if the sleeve-cap height is low by 50% and as 50% of the additional size in the standing position if the sleeve-cap height is 80%.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.8
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• pp.1142-1149
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• 2003

The present study describes a numerical analysis for simulation of the sloshing of flows with free-surface which contained in a rectangular tank moving in harmonic or pitching motion. The VOF function, representing the volume fraction of a cell occupied by the fluid, is calculated for each cells, which gives the location of the free-surface filling any some fraction of cells with fluid. 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. Damping effects by baffles were extensively investigated for various conditions in terms of baffle shape and position.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.10 s.241
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• pp.1336-1343
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• 2005

The detection mechanism of the flaw for the nondestructive testing using eddy current is related to the interaction of the induced eddy currents in the test specimen with flaws and the coupling of these interaction effects with the moving test probe. In this study, the two-dimensional electromagnetic finite element analysis(FEM) fur the eddy current signals of the aluminum plate with different depth of surface cracks is described and the comparison is also made between experimental and predicted signals analyzed by FEM. In addition, the characteristics of attenuation of the eddy current density due to the variation of the depth of a conductor are evaluated. The effective parameters for the application of eddy current technique to evaluate surface cracks are discussed by analyzing the characteristics of the eddy current signals due to the variation of crack depths.

• Journal of the Society of Naval Architects of Korea
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• v.29 no.4
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• pp.66-74
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• 1992

A panel method in the spirit of Hess & Smith(1962), and also of Dawson(1977) was developed to compute the wave resistance of a submerged, or a surface piercing, body moving in the water of finite depth. As a boundary condition on the free surface what is called the Poisson equation is used, while Yasukawa(1989) chose the Dawson equation for which the double-body flow is regarded as the basic one. In order to satisfy the boundary condition on the bottom surface automatically, the sum of a Rankine source and its image with respect to the bottom surface is chosen as the Green function, and hence the singularity is distributed only on the body and on the free surface thereby decreasing the required number of panels dramatically, compared to that of Yasukawa, without the consequential loss of accuracy. Calculations were done for a submerged sphere and for the Wigley hull, and the results are compared with other existing analytical and numerical data.

• Journal of the Korea Institute of Military Science and Technology
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• v.12 no.1
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• pp.8-17
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• 2009

This paper proposes robust ship wake search method in the target evasion environment. Moving surface ships generate a long trailing wake in the rear of a surface ship. Wake homing torpedo sensing this wake can detect the surface target and engage it automatically. In wake homing torpedo, wake search method is important element to maximize effectiveness of wake homing torpedo. This paper proposes one-side, two-side and centering mode according to passing wake boundary scenarios. Also, wake deflection angle is deduced by using the principle of deflection angle of acoustic torpedo. The representative experimental results using monte-carlo simulation demonstrate that the searching method using one-side mode is superior to two-side and centering mode in the target evasion environment.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.5
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• pp.543-551
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• 2011

The paper deals with the comparative study of design optimization based on various approximation techniques in strength design of riser support structure installed on floating production storage and offloading unit(FPSO) using offshore operation loading conditions. The design optimization problem is formulated such that structural member sizing variables are determined by minimizing the weight of riser support structure subject to the constraints of structural strength in terms of loading conditions. The approximation techniques used in the comparative study are response surface method based sequential approximate optimization(RBSAO), Kriging based sequential approximate optimization(KBSAO), and the enhanced moving least squares method(MLSM) based approximate optimization such as CF(constraint feasible)-MLSM and Post-MLSM. Commercial process integration and design optimization(PIDO) tools are employed for the applications of RBSAO and KBSAO. The enhanced MLSM based approximate optimization techniques are newly developed to ensure the constraint feasibility. In the context of numerical performances such as design solution and computational cost, the solution results from approximate techniques based design optimization are compared to actual non-approximate design optimization.