• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.7
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• pp.867-876
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• 2003

The Lagrangian dispersion of fluid particles in inhomogeneous turbulence is investigated by a direct numerical simulation of turbulent channel flow. Four points Hermite interpolation in the homogeneous direction and Chebyshev polynomials in the inhomogeneous direction is adopted to simulate the fluid particle dispersion. An inhomogeneity of Lagrangian statistics in turbulent boundary layer is investigated by releasing many particles at several different wall-normal locations and tracking those particles. The fluid particle dispersions and Lagrangian structure functions of velocity are scaled by the Kolmogorov similarity. The auto-correlations of velocity and acceleration are shown at the different releasing locations. Effect of initial particle location on the dispersion is analyzed by the probability density function at the several downstreams and time instants.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2000.04a
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• pp.167-168
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• 2000

복잡한 구조를 갖고 시간에 따라서 변하는 바람장내에서 공장굴뚝과 같은 점오염원에서 배출되는 오염물질의 확산을 계산하기 위해서 라그란지안 입자확산모텔(Lagrangian Particle Dispersion Model, LPDM)을 사용하는 것이 최근의 연구 동향이다. 구윤서(1999a, 1999b)는 중립 및 안정한 대기조건에서 바람장 계산시 비평형 2.5 난류모델을 이용한 LPDM을 개발하여 복잡한 대기흐름내 확산현상을 보다 정확히 모사할 수 있는 LPDM을 제시하였다. (중략)

• Journal of the Korea Institute of Military Science and Technology
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• v.5 no.2
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• pp.207-216
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• 2002

In this paper, the study on the behavior of the deformation of brittle material, such as concrete, ceramic, was peformed by comparison of Lagrangian technique and Smoothed Particle Hydrodynamics using commercial nonlinear hydrodynamic numerical program, Autodyn_2D. The effect of SPH technique was proved by investigating the behavior of material deformation, velocity profile and pressure profile.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 1996.04a
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• pp.151-155
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• 1996

• Proceedings of the Korea Air Pollution Research Association Conference
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• 1998.10a
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• pp.266-267
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• 1998

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.899-904
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• 2003

A new model for dense gas dispersion is formulated within the Lagrangian framework. In several accidental released situations, denser-than-air vapour clouds are formed which exhibit dispersion behavior markedly different from that observed for passive atmospheric pollutants. For relevant prediction of dense gas dispersion, the gravity and entrainment effects need to implemented. The model deals with negative buoyancy which is affected by gravity. Also, the model is subjected to entrainment. The mean downward motion of each particle was accounted for by considering the Langevin equation with buoyancy correction term.

• Journal of Ocean Engineering and Technology
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• v.14 no.1
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• pp.1-5
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• 2000

A numerical analysis for wave motion in the shallow water is presented. The method is based on potential theory. The fully nonlinear free surface boundary condition is assumed in an inner domain and this solution is matched along an assumed common boundary to a linear solution in outer domain. In two-dimensional problem Cauchy's integral theorem is applied to calculate the complex potential and its time derivative along boundary.

• Journal of Ocean Engineering and Technology
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• v.8 no.2
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• pp.151-156
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• 1994

The equations of motion of a submarine pipeline with the internal flowing fluid and subject to hydrodynamic loadings are derived by using Hamilton's principle. Coupling between the bending and the longitudinal extension due to axial load and thermal expansion are considered. Coupling between the twisting and extension are not considered. The equations of motion are well agreed with the results which are derived by the vector method.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1995.09a
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• pp.300-324
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• 1995

This research investigates the automatic identification of typical embedded structures in the Integer Programming(IP) models and automatic transformation of the problem to an adequate Lagrangian problem which can provide tight bounds within the acceptable run time. For this purpose, the structural distinctiveness of variables, constants, blocks of terms, and constraint chunks is identified to describe the structure of the IP model. To assist the identification of the structural distinctiveness, the representation by the knowledge based IP model formulator UNIK-IP is adopted. For the reasoning for the structural identification, the bottom-up, top-down, and case-based approaches are proposed. A prototype system UNIK-RELAX is developed to implement the approaches proposed in this research.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.7
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• pp.859-866
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• 2003

The Lagrangian dispserion of fluid particles in inhomogeneous turbulence is investigated by a direct numerical simulation of turbulent channel flow. Fluid particle velocity and acceleration along a particle trajectory are computed by employing several interpolation schemes such as linear interpolation, high-order Lagrange polynomial interpolation and the Hermite interpolation schemes. The performances of the schemes are evaluated through comparison of errors in computed particle positions, velocities and accelerations against spectral interpolation. Adopting the four-point Hermite interpolation in the homogeneous directions and Chebyshev polynomials in the wall-normal direction appears to produce most reliable Lagrangian statistics including acceleration correlations with a reasonable amount of computational overhead.