• Title/Summary/Keyword: Hydrodynamics code

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Collision Simulation of a Floating Offshore Wind Turbine Considering Ductile Fracture and Hydrodynamics Using Hydrodynamic Plug-in HydroQus

  • Dong Ho Yoon;Joonmo Choung
    • Journal of Ocean Engineering and Technology
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    • v.37 no.3
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    • pp.111-121
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    • 2023
  • This paper intends to introduce the applicability of HydroQus to a problem of a tanker collision against a semi-submersible type floating offshore wind turbine (FOWT). HydroQus is a plug-in based on potential flow theory that generates interactive hydroforces in a commercial Finite element analysis (FEA) code Abaqus/Explicit. Frequency response analyses were conducted for a 10MW capacity FOWT to obtain hydrostatic and hydrodynamic constants. The tanker was modeled with rigid elements, while elastic-plastic elements were used for the FOWT. Mooring chains were modeled to implement station keeping ability of the FOWT. Two types of fracture models were considered: constant failure strain model and combined failure strain model HC-LN model composed of Hosford-Coulomb (HC) model & localized necking (LN) model. The damage extents were evaluated by hydroforces and failure strain models. The largest equivalent plastic strain observed in the cases where both restoring force and radiation force were considered. Stress triaxiality and damage indicator analysis showed that the application of HC-LN model was suitable. It could be stated that applications of suitable failure strain model and hydrodynamics into the collision simulations were of importance.

Computational fluid dynamic simulation with moving meshes

  • Yun, Kiyun;Kim, Juhan;Yoon, Suk-Jin
    • The Bulletin of The Korean Astronomical Society
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    • v.38 no.2
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    • pp.101.2-101.2
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    • 2013
  • We present a new computational fluid dynamic (CFD) simulation code. The code employs the moving and polyhedral unstructured mesh scheme, which is known as a superior approach to the conventional SPH (smoothed particle hydrodynamics) and AMR (adaptive mesh refinement) schemes. The code first generates unstructured meshes by the Voronoi tessellation at every time step, and then solves the Riemann problem for surfaces of every Voronoi cell to update the hydrodynamic states as well as to move former generated meshes. For the second-order accuracy, the MUSCL-Hancock scheme is implemented. To increase efficiency for generating Voronoi tessellation we also develop the incremental expanding method, by which the CPU time is turned out to be just proportional to the number of particles, i.e., O(N). We will discuss the applications of our code in the context of cosmological simulations as well as numerical experiments for galaxy formation.

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Unstructured Moving-Mesh Hydrodynamic Simulation

  • Yun, Kiyun;Kim, Juhan;Yoon, Suk-Jin
    • The Bulletin of The Korean Astronomical Society
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    • v.39 no.2
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    • pp.65.2-65.2
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    • 2014
  • We present a new hydrodynamic simulation code based on the Voronoi tessellation for estimating the density precisely. The code employs both of Lagrangian and Eulerian description by adopting the movable mesh scheme, which is superior to the conventional SPH (smoothed particle hydrodynamics) and AMR (adaptive mesh refinement) schemes. The code first generates unstructured meshes by the Voronoi tessellation at every time step, and then solves the Riemann problem for all surfaces of each Voronoi cell so as to update the hydrodynamic states as well as to move current meshes. Besides, the IEM (incremental expanding method) is devised to compute the Voronoi tessellation to desired degree of speed, thereby the CPU time is turned out to be just proportional to the number of particles, i.e., O(N). We discuss the applications of our code in the context of cosmological simulations as well as numerical experiments for galaxy formation.

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An Implementation of the Adaptive Ray Tracing Method in the Athena Code

  • Kim, Jeong-Gyu;Kim, Woong-Tae;Ostriker, Eve C.
    • The Bulletin of The Korean Astronomical Society
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    • v.41 no.1
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    • pp.50.1-50.1
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    • 2016
  • The incorporation of radiation from massive stars is essential for modeling the dynamics and chemistry of star-forming clouds, yet it is a computationally demanding task for three-dimensional problems. We describe the implementation and tests of radiative transfer module due to point sources on a three-dimensional Cartesian grid in the Eulerian MHD code Athena. To solve the integral form of the radiation transfer equation, we adopt a widely-used long characteristics method with spatially adaptive ray tracing in which rays are split when sampling of cells becomes coarse. We use a completely asynchronous communication pattern between processors to accelerate transport of rays through a computational domain, a major source of performance bottleneck. The results of strong and weak scaling tests show that our code performs well with a large number of processors. We apply our radiation hydrodynamics code to some test problems involving dynamical expansion of HII regions.

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Effect of Solid Mass Inventory on Hydrodynamics Characteristics in a Circulating Fluidized Bed (순환유동층에서 유동매체량에 따른 수력학적 특성 연구)

  • Kim, E.K.;Shin, D.;Lee, J.;Kim, J.;Hwang, J.
    • Journal of the Korean Society of Combustion
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    • v.7 no.4
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    • pp.10-20
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    • 2002
  • This paper discusses effect of solid mass inventory on the hydrodynamic characteristics of circulating fluidized bed(CFB). Operating parameters of solid mass inventory and air flow rates were varied to understand their effects on fludization pattern. Experimental measurements were made in a CFB of which height and diameter are 3m and 0.05m respectively. Black SiC particles ranging from $100{\mu}m\;to\;500{\mu}m$ were employed as the bed material. Superficial gas velocity of riser and J-valve fluidizing velocity were in the ranges of $1.39{\sim}3.24m/s\;and\;0.139{\sim}0.232m/s$, respectively. The axial solid fraction and solid circulation rate of CFB were calculated based on the experimental data and compared with modellings through IEA-CFBC Model and commercial CFD code.

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Smoothed Particle Hydrodynamics Code Basics

  • MONAGHAN J. J.
    • Journal of The Korean Astronomical Society
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    • v.34 no.4
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    • pp.203-207
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    • 2001
  • SPH is the shorthand for Smoothed Particle Hydrodynamics. This method is a Lagrangian method which means that it involves following the motion of elements of fluid. These elements have the characteristics of particles and the method is called a particle method. A useful review of SPH (Monaghan 1992) gives the basic technique and how it can be applied to numerous problems relevant to astrophysics. You can get some basic SPH programs from http) /www.maths.monash.edu.au/jjm/sphlect In the present lecture I will assume that the student has studied this review and therefore understands the basic principles. In today's lecture I plan to approach the equations from a different perspective by using a variational principle.

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A study of sub-galactic scale structure formation with a cosmological hydro code

  • Shin, Ji-Hye;Kim, Ju-Han;Kim, Sung-Soo S.;Yoon, Suk-Jin
    • The Bulletin of The Korean Astronomical Society
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    • v.36 no.2
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    • pp.57.2-57.2
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    • 2011
  • To study the formation and evolution of sub-galactic scale structures, we have added SPH (Smoothed Particle Hydrodynamics) method into an existing cosmological PMTree code, GOTPM. To follow the evolution of gas particles, we consider heating/cooling processes, star formation, and energy & metal feedback by supernova explosion. We have performed various tests for the new code and found that the results reproduce observed quantities or follow the known analytic solutions. We present a test simulation of isolated disk galaxy with a focus on whether the star formation reproduces the observed features.

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Effects of large-scale structures on cosmological hydrodynamic simulations

  • Shin, Jihye;Park, Changbom;Kim, Juhan
    • The Bulletin of The Korean Astronomical Society
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    • v.42 no.2
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    • pp.56.2-56.2
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    • 2017
  • We in the Korea Institute for Advanced Study are preparing the fifth Horizon Run in a series of large-scale cosmological simulations. For the first time we will include full hydrodynamics and astrophysical processes using a RAMSES code. I will discuss the impact of large-scale structures on smaller scale properties in cosmological hydrodynamic simulation to justify our choice of simulation boxsize, whose one side length is up to 1 Gpc.

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Hydrodynamic Characteristics of Vaned-Diffuser and Return-Channel for a Multistage Centrifugal Pump (원심다단펌프용 디퓨저-리턴채널의 유동특성)

  • Oh, Hyoung-Woo
    • The KSFM Journal of Fluid Machinery
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    • v.14 no.6
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    • pp.54-60
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    • 2011
  • This paper presents the steady-state performance analysis of the first stage of a multistage centrifugal pump, composed of a shrouded-impeller, a vaned-diffuser and a return-channel, using the commercially available computational fluid dynamics (CFD) code, ANSYS CFX. The detailed flow fields in the vaned-diffuser with outlet in its side wall and the return-channel are investigated by the CFD code adopted in the present study. The effect of the vaned-diffuser with a downstream crossover bend and the corresponding return-channel on the overall hydrodynamic performance of the first stage pump has also been demonstrated over the normal operating conditions. The predicted hydrodynamics for the diffusing components herein could provide useful information to match the inlet blade angle of the next stage impeller for improving the multistage pump performances.

Diffusive Shock Acceleration with Self-Consistent Injection

  • KANG HYESUNG
    • Journal of The Korean Astronomical Society
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    • v.34 no.4
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    • pp.293-295
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    • 2001
  • A numerical scheme that incorporates a self-consistent cosmic-ray (CR, hereafter) injection model into the combined gas dynamics and CR diffusion-convection code has been developed. The hydro/CR code can follow in a very cos-effective way the evolution of CR modified shocks by adopting subzone shock-tracking and multi-level Adaptive Mesh Refinement techniques. The injection model is based on interactions of the suprathermal particles with self-generated MHD waves in quasi-parallel shocks. The particle injection is followed numerically by filtering the diffusive flux of suprathermal particles across the shock to upstream region according to a velocity-dependent transparency function, which represents the fraction of leaking suprathermal particles. In the strong shock limit of Mach numbers $\ge$20, significant physical processes such as the injection and acceleration seem to become independent of M, while they are sensitively dependent on M for M < 10. Although some particles injected early in the evolution continue to be accelerated to higher energies, the postshock CR pressure reaches a time asymptotic value due to balance between acceleration and diffusion of the CR particles.

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