• Title, Summary, Keyword: Hydrodynamics

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Numerical Modeling of the Detonation of Explosives Using Hydrodynamics Codes (유체 동역학 코드를 이용한 화약의 폭발과정에 대한 수치 모델링)

  • Park, Dohyun;Choi, Byung-Hee
    • Explosives and Blasting
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    • v.34 no.2
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    • pp.31-38
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    • 2016
  • The hydrodynamics code is a numerical tool developed for modeling high velocity impacts where the materials are assumed to behave like fluids. The hydrodynamics code is widely used for solving impact problems, such as rock blasting using explosives. For a realistic simulation of rock blasting, it is necessary to model explosives numerically so that the interaction problem between rock and explosives can be solved in a fully coupled manner. The equation of state of explosives, which describes the state of the material under given physical conditions, should be established. In this paper, we introduced the hydrodynamics code used for explosion process modeling, the equation of state of explosives, and the determination of associated parameters.

A Study on the technique of impact analysis against concrete target using Lagrangian and Smoothed Particle Hydrodynamics (라그란지안 기법과 입자완화동력학 기법을 이용한 콘크리트 표적 충돌해석 기법 연구)

  • 하동호
    • 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.

Hydrodynamics prediction of a ship in static and dynamic states

  • Du, P.;Ouahsine, A.;Sergent, P.
    • Coupled systems mechanics
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    • v.7 no.2
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    • pp.163-176
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    • 2018
  • The ship hydrodynamics in static and dynamic states were investigated using 3-dimensional numerical simulations. The static case simulated a fixed ship, while the dynamic case considered a ship with free sinkage and trim using the mesh morphing technique. High speed was found to increase the wave elevation around the ship. Compared with the static case, the dynamic case seemed to generate higher waves near the bow and after the stern. The frictional resistance was found be to more dominant. However, the pressure resistance became gradually important with the increase of the ship speed. The trim and sinkage were also analyzed to characterize the ship hydrodynamics in the dynamic state.

Numerical hydrodynamic analysis of an offshore stationary-floating oscillating water column-wave energy converter using CFD

  • Elhanafi, Ahmed;Fleming, Alan;Macfarlane, Gregor;Leong, Zhi
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.9 no.1
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    • pp.77-99
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    • 2017
  • Offshore oscillating water columns (OWC) represent one of the most promising forms of wave energy converters. The hydrodynamic performance of such converters heavily depends on their interactions with ocean waves; therefore, understanding these interactions is essential. In this paper, a fully nonlinear 2D computational fluid dynamics (CFD) model based on RANS equations and VOF surface capturing scheme is implemented to carry out wave energy balance analyses for an offshore OWC. The numerical model is well validated against published physical measurements including; chamber differential air pressure, chamber water level oscillation and vertical velocity, overall wave energy extraction efficiency, reflected and transmitted waves, velocity and vorticity fields (PIV measurements). Following the successful validation work, an extensive campaign of numerical tests is performed to quantify the relevance of three design parameters, namely incoming wavelength, wave height and turbine damping to the device hydrodynamic performance and wave energy conversion process. All of the three investigated parameters show important effects on the wave-pneumatic energy conversion chain. In addition, the flow field around the chamber's front wall indicates areas of energy losses by stronger vortices generation than the rear wall.

High Density Crowd Simulation based on SPH (Smoothed Particle Hydrodynamics 기반 고 밀집 군중 시뮬레이션 기법)

  • Kang, Shin-Jin;Lee, Jung;Kim, Soo-Kyun
    • Journal of Korea Game Society
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    • v.11 no.6
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    • pp.193-199
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    • 2011
  • Producing high density crowd simulation is time-consuming task as increasing the number of individuals in the crowds. In this paper, we propose a new control technique that can create realistic high density crowd simulation by using Smoothed Particle Hydrodynamics (SPH) method from fluid simulation field. Equations in SPH method are modified for evacuation, distance maintenance, and group maintenance forces for individual behaviors in the crowds. Experimental results showed that the proposed system could enable natural high density crowd simulation efficiently.

Molten Metal Flow Analysis of Casting Process Using SPH Method (SPH 기법을 이용한 주조공정 용탕 주입 유동 해석)

  • Park, Byung Lae;Lee, Sang Wook
    • Journal of the Korean Society of Visualization
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    • v.16 no.1
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    • pp.54-60
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    • 2018
  • It is important to develop more efficient and productive casting processes for an automated high precision molten-metal casting system. Detailed analysis of molten-metal flow in the casting process by the numerical approach will help to optimize the control of a ladle. In this study, the smoothed particle hydrodynamics method was applied to analyze casting flow characteristics with different tilting angular speed and initial molten-metal level. The smoothed particle hydrodynamics technique has advantages to easily handle non-linear free surface behavior with the absence of a computational mesh. We found that tilting angular speed has relatively greater effect on the casting flowrate and that the effect of the initial molten-metal level is only minor. Further extensive study will be necessary to find an optimal condition for high efficient casting system.

GENERAL RELATIVISTIC RADIATION HYDRODYNAMICS: FREQUENCY-INTEGRATED RADIATION MOMENT FORMALISM

  • Park, Myeong-Gu
    • Journal of The Korean Astronomical Society
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    • v.45 no.4
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    • pp.101-110
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    • 2012
  • I present here one approach to general relativistic radiation hydrodynamics. It is based on covariant tensor conservation equations and considers only the frequency-integrated total energy and momentum exchange between matter and the radiation field. It is also a mixed-frame formalism in the sense that, the interaction between radiation and matter is described with quantities in the comoving frame in which the interaction is often symmetric in angle while the radiation energy and momentum equations are expressed in the fixed frame quantities in which the derivatives are simpler. Hence, this approach is intuitive enough to be applied straightforwardly to any spacetime or coordinate. A few examples are provided along with caveats in this formalism.

Gas-liquid interface treatment in underwater explosion problem using moving least squares-smoothed particle hydrodynamics

  • Hashimoto, Gaku;Noguchi, Hirohisa
    • Interaction and multiscale mechanics
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    • v.1 no.2
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    • pp.251-278
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    • 2008
  • In this study, we investigate the discontinuous-derivative treatment at the gas-liquid interface in underwater explosion (UNDEX) problems by using the Moving Least Squares-Smoothed Particle Hydrodynamics (MLS-SPH) method, which is known as one of the particle methods suitable for problems where large deformation and inhomogeneity occur in the whole domain. Because the numerical oscillation of pressure arises from derivative discontinuity in the UNDEX analysis using the standard SPH method, the MLS shape function with Discontinuous-derivative Basis Function (DBF) that is able to represent the derivative discontinuity of field function is utilized in the MLS-SPH formulation in order to suppress the nonphysical pressure oscillation. The effectiveness of the MLS-SPH with DBF is demonstrated in comparison with the standard SPH and conventional MLS-SPH though a shock tube problem and benchmark standard problems of UNDEX of a trinitrotoluene (TNT) charge.