• 제목/요약/키워드: Hydrodynamics code

검색결과 70건 처리시간 0.027초

Development of a New Cosmological Hydro Simulation Code

  • 김주한;신지혜;김성수;박창범
    • 천문학회보
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    • 제36권2호
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    • pp.52.1-52.1
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    • 2011
  • We have implemented the Smoothed Particle Hydrodynamics (SPH) into the cosmological N-body simulation code. The pre-initial particle distribution is set to follow the glacial conditions and the initial temperature of hydro particles is calculated based on the adiabatic process in the expanding backgrounds. Typical adiabatic SPH equations are adopted and, additionally, non-adiabatic processes such as heating/cooling and supernova explosion are added. We study the effect of star formation criteria on the global star formation rate and compare it with the observations.

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DEVELOPMENT OF AN LES METHODOLOGY FOR COMPLEX GEOMETRIES

  • Merzari, Elia;Ninokata, Hisashi
    • Nuclear Engineering and Technology
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    • 제41권7호
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    • pp.893-906
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    • 2009
  • The present work presents the development of a Large Eddy Simulation (LES) methodology viable for complex geometries and suitable for the simulation of rod-bundles. The use of LES and Direct Numerical Simulation (DNS) allows for a deeper analysis of the flow field and the use of stochastical tools in order to obtain additional insight into rod-bundle hydrodynamics. Moreover, traditional steady-state CFD simulations fail to accurately predict distributions of velocity and temperature in rod-bundles when the pitch (P) to diameter (D) ratio P/D is smaller than 1.1 for triangular lattices of cylindrical pins. This deficiency is considered to be due to the failure to predict large-scale coherent structures in the region of the gap. The main features of the code include multi-block capability and the use of the fractional step algorithm. As a Sub-Grid-Scale (SGS) model, a Dynamic Smagorinsky model has been used. The code has been tested on plane channel flow and the flow in annular ducts. The results are in excellent agreement with experiments and previous calculations.

A Numerical Simulation for Contractive and Dilative Periodic Motion on Axisymmetric Body

  • Kim, Moon-Chan
    • Journal of Ship and Ocean Technology
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    • 제3권1호
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    • pp.1-11
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    • 1999
  • Numerical simulation for the axisymmetric body with contractive and dilative periodic motion is carried out. The present analysis shows that a propulsive force can be obtained in highly viscous fluid by the contractive and dilative motion of axisymmetric body. An axisymmetric code is developed with unstructured grid system for the simulation of complicated motion and geometry. It is validated by comparing with the results of Stokes approximation with the problem of uniform flow past a sphere in low Reynolds number($R_n$ = 1). The validated code is applied to the simulation of contractive and dilative periodic motion of body whose results are quantitatively compared with the two dimensional case. The simulation is extended to the analysis of waving surface with projecting part for finding out the difference of hydrodynamics performance according to variation of waving surface configuration. The present study will be the basic research for the development of the propulsor of an axisymmetric micro-hydro-machine.

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Morphology and Dynamical Properties of Ultra-Relativistic Jets

  • Seo, Jeongbhin;Kang, Hyesung;Ryu, Dongsu
    • 천문학회보
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    • 제45권1호
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    • pp.37.2-37.2
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    • 2020
  • We study the structures and dynamics of flows generated by ultra-relativistic jets on kpc scales through three-dimensional relativistic hydrodynamics (RHD) simulations. We employ a newly developed RHD code, equipped with the WENO-Z reconstruction, the SSPRK time discretization, and an equation of state that closely approximates the single-component perfect gas in relativistic regime. Exploring a set of models with various parameters, we confirm that the well-known Fanaroff-Riley dichotomy is primarily determined by the jet power, whereas the morphology of simulated jets also depends on the secondary parameters such as the momentum injection rate and the ratio of the jet to background pressure. Utilizing high resolution capabilities of the newly developed code, we examine in detail the dynamical properties of complex flows in different parts of jet-produced structures, and present the statistics of nonlinear dynamics such as shock, shear, and turbulence.

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Damage identification of masonry arch bridge under blast loading using smoothed particle hydrodynamics (SPH) method

  • Amin Bagherzadeh Azar;Ali Sari
    • Structural Engineering and Mechanics
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    • 제91권1호
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    • pp.103-121
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    • 2024
  • The smoothed particle hydrodynamics (SPH) method is a numerical technique used in dynamic analysis to simulate the fluid-like behavior of materials under extreme conditions, such as those encountered in explosions or high velocity impacts. In SPH, fluid or solid materials are discretized into particles. These particles interact with each other based on certain smoothing kernels, allowing the simulation of fluid flows and predict the response of solid materials to shock waves, like deformation, cracking or failure. One of the main advantages of SPH is its ability to simulate these phenomena without a fixed grid, making it particularly suitable for analyzing complex geometries. In this study, the structural damage to a masonry arch bridge subjected to blast loading was investigated. A high-fidelity micro-model was created and the explosives were modeled using the SPH approach. The Johnson-Holmquist II damage model and the Mohr-Coulomb material model were considered to evaluate the masonry and backfill properties. Consistent with the principles of the JH-II model, the authors developed a VUMAT code. The explosive charges (50 kg, 168 kg, 425 kg and 1000 kg) were placed in close proximity to the deck and pier of a bridge. The results showed that the 50 kg charges, which could have been placed near the pier by a terrorist, had only a limited effect on the piers. Instead, this charge caused a vertical displacement of the deck due to the confinement effect. Conversely, a 1000 kg TNT charge placed 100 cm above the deck caused significant damage to the bridge.

섬진강 하구역 Mobile MGIS 구축 연구 (Mobile MGIS Study for the Seomjin River Estuary)

  • 박상우;김정현;김종규
    • 수산해양교육연구
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    • 제28권1호
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    • pp.172-179
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    • 2016
  • The study of Mobile MGIS (Marine Geographic Information System) based on the Android Mobile Platform is mainly performed on effective methodologies which transform real world data to computing world data. Mobile GUI system has its own target on reliable data service by acquisition of geometric information using EFDC (Environmental Fluid Dynamics Code) Model, accurate measurement and graphical visualization. Even simple visualizations can aid in the interpretation of complex hydrodynamic relationships that are frequently encountered in the marine environment. The Mobile MGIS provides an easy way for hydrodynamics geoscientists to construct complex visualizations that can be viewed with free software. This study proposes a Mobile GUI MGIS using EFDC Model result of Seomjin River estuary. Finally, we design a Seomjin River estuarine Coastal Waters Mobile MGIS integrating above data models. It must adds more ecological information and the various service item for approach more easily in order to user.

Numerical Study of AGN Jet Propagation with Two Dimensional Relativistic Hydrodynamic Code

  • MIZUTA AKIRA;YAMADA SHOICHI;TAKABE HIDEAKI
    • 천문학회지
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    • 제34권4호
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    • pp.329-331
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    • 2001
  • We investigate the morphology of Active Galactic Nuclei(AGN) jets. AGN jets propagate over kpc $\~$ Mpc and their beam velocities are close to the speed of light. The reason why many jets propagate over so long a distance and sustain a very collimated structure is not well understood. It is argued that some dimensionless parameters, the density and the pressure ratio of the jet beam and the ambient gas, the Mach number of the beam, and relative speed of the beam compared to the speed of light, are very useful to understand the morphology of jets namely, bow shocks, cocoons, nodes etc. The role of each parameters has been studied by numerical simulations. But more research is necessary to understand it systematically. We have developed 2D relativistic hydrodynamic code to analyze relativistic jets. We pay attention to the propagation velocity which is derived from 1D momentum balance in the frame of the working surface. We show some of our models and discuss the dependence of the morphology of jets on the parameter.

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COSMIC RAY ACCELERATION AT COSMOLOGICAL SHOCKS: NUMERICAL SIMULATIONS OF CR MODIFIED PLANE-PARALLEL SHOCKS

  • KANG HYESUNG
    • 천문학회지
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    • 제36권3호
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    • pp.111-121
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    • 2003
  • In order to explore the cosmic ray acceleration at the cosmological shocks, we have performed numerical simulations of one-dimensional, plane-parallel, cosmic ray (CR) modified shocks with the newly developed CRASH (Cosmic Ray Amr SHock) numerical code. Based on the hypothesis that strong Alfven waves are self-generated by streaming CRs, the Bohm diffusion model for CRs is adopted. The code includes a plasma-physics-based 'injection' model that transfers a small proportion of the thermal proton flux through the shock into low energy CRs for acceleration there. We found that, for strong accretion shocks with Mach numbers greater than 10, CRs can absorb most of shock kinetic energy and the accretion shock speed is reduced up to $20\%$, compared to pure gas dynamic shocks. Although the amount of kinetic energy passed through accretion shocks is small, since they propagate into the low density intergalactic medium, they might possibly provide acceleration sites for ultra-high energy cosmic rays of $E\ll10^{18}eV$. For internal/merger shocks with Mach numbers less than 3, however, the energy transfer to CRs is only about $10-20\%$ and so nonlinear feedback due to the CR pressure is insignificant. Considering that intracluster medium (ICM) can be shocked repeatedly, however, the CRs generated by these weak shocks could be sufficient to explain the observed non-thermal signatures from clusters of galaxies.

Direct strength evaluation of the structural strength of a 500 cbm LNG bunkering ship

  • Muttaqie, Teguh;Jung, DongHo;Cho, Sang-Rai;Sohn, Jung Min
    • Structural Engineering and Mechanics
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    • 제81권6호
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    • pp.781-790
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    • 2022
  • The present paper describes a general procedure of the structural safety assessment for the independent type C tank of LNG bunkering ship. This strength assessment procedure consists of two main scheme, global Finite Element Analysis (FEA) model primarily for hull structure assessment and detailed LNG Tank structures FEA model including the cylindrical tank itself and saddle-support structures. Two kinds of mechanism are used, fixed and slides constraints in fore and rear of the saddle-support structures that result in a variation of the reaction forces. Finite Element (FE) analyses have been performed and verified by the strength acceptance criteria to evaluate the safety adequacy of yielding and buckling of the hull and supporting structures. The detail of FE model for an LNG type C tank and its saddle supports was made, which includes the structural members such as cylindrical tank shell, ring stiffeners, swash bulkhead, and saddle supports. Subsequently, the FE buckling analysis of the Type C tank has been performed under external pressure following International Gas Containment (IGC) code requirements. Meanwhile, the assessment is also performed for yielding and buckling strength evaluation of the cylindrical LNG tank according to the PD 5500 unfired fusion welded pressure vessels code. Finally, a complete procedure for assessing the structural strength of 500 CBM LNG cargo tank, saddle support and hull structures have been provided.

Star Formation of Merging Disk Galaxies with AGN Feedback Effects

  • Park, Jongwon;Smith, Rory;Yi, Sukyoung K.
    • 천문학회보
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    • 제42권1호
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    • pp.28.2-28.2
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    • 2017
  • Using numerical hydrodynamics code RAMSES, we perform idealized galaxy merger simulations and study the star formation of merging disk galaxies. In our simulations, we consider the active galactic nucleus (AGN) feedback effect. In order to investigate the star formation influenced by AGN, we run ~60 simulations with various initial conditions. We confirm that star formation is more efficiently suppressed in merging galaxies than in isolated galaxies. In the mergers, AGN effect is more significant when the masses of two galaxies are similar. Furthermore, we find that bulge fraction does not affect the star formation when the AGN effect is considered. We discuss the implications on semi-analytic galaxy formation models and the limitation of the current AGN prescriptions.

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