• Journal of the Society of Naval Architects of Korea
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• v.54 no.6
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• pp.470-475
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• 2017

Since the intake air of gas turbine engine of marine purpose contains water particles, inertial separator for separating the air and water particles are provided. Saw type and wave type separator are now used to separate inflow water particle from the gas. In this paper, the design parameters of saw type separator are studied by numerical simulations. Using the commercial CFD program, Star-CCM+, Lagrangian-Eulerian method was used to perform the analysis of two phase flow of the mist in the air. This method solves Reynolds-Averaged Navier-Stokes equations in Eulerian framework for the continuous phase, while solves equation of motion for individual particles in Lagrangian framework. Lagrangian multiphase method was applied to monitor the particles of different sizes and shapes and to verify collision between particles by chasing particles. Water particles were injected through injectors located at the inlet of the separator and escape mode was used which assumes that the particles attached on the surface of inertial separator were removed from the simulation, effectively escaping the solution domain. Through the numerical computations with the inlet condition of constant water particle size in the wetness fraction of 85%, efficiency of eliminating the water particle and the pressure drop between the inlet and outlet were examined.

• Journal of computational fluids engineering
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• v.11 no.1 s.32
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• pp.29-35
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• 2006

A code is developed to analyze a spherically symmetric underwater explosion. The arbitrary Lagrangian-Eulerian(ALE) Godunov scheme for two-phase flow is used to calculate numerical fluxes through moving control surfaces. For detonation gas of TNT and liquid water, the Jones-Wilkins-Lee(JWL) equation of states and the isentropic Tait relation are used respectively. It is suggested to use the Godunov variable to estimate the velocity of a material interface. The code is validated through comparisons with other results on the gas-water shock tube problem. It is shown that the code can handle generation of discontinuity and recovering of continuity in the normal velocity near the material interface during shock waves interact with the material interface. The developed code is applied to analyze a spherically symmetric underwater explosion. Repeated transmissions of shock waves are clearly captured. The calculated period and maximum radius of detonation gas bubble show good agreements with experimental and other numerical results.

• Journal of the Korean Geotechnical Society
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• v.29 no.6
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• pp.77-86
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• 2013

Embankments on soft ground experience significant deformation during time-dependent consolidation settlement, as well as an initial undrained settlement. Since infinitesimal strain theory assumes no configuration change and minute strain during deformation, finite strain analysis is required for better prediction of geotechnical problems involving large strain and geometric change induced by imposed loadings. Updated Lagrangian formulation is developed for time-dependent consolidation combining both force equilibrium and mass conservation of fluid, and mechanical constitutive equation is written in Janumann stress rate. Numerical convergence during Newton's iteration in large deformation analysis is improved by Nagtegaal's approach of considering the effect of rotation in mechanical constitutive relationship. Numerical simulations are conducted to discuss numerical reliability and applicability of developed numerical code: deformation of cantilever beam, two-dimensional consolidation. The numerical results show that developed formulation can efficiently describe large deformation problems. Proposed formulation is expected to facilitate the upgrading of a numerical code based on infinitesimal strain theory to that based on finite strain analysis.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.6
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• pp.663-673
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• 2011

In this study, we analysed the effect of the fire source in the warehouse under the bridge and the height of the bridge using FDS code. To compare accuracy of simulation results, we simulated the experimental result with unit combustibles which is heptane as well as the mock-up test. Using this method, we evaluated the fire safety of the bridge which contains spalling and strength damage of concrete as well as damage of reinforcements according to the fire source and the height of the bridge. Most of the bridges are vulnerable to spalling of concrete. The book combustion has the strongest fire intensity which is expected to damage the bridge less than 30m height in the three types of the fire sources. The bridge over the 30m height can ensure the fire safety in the case of the rubber combustion.

• Journal of Korean Society on Water Environment
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• v.29 no.3
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• pp.383-392
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• 2013

In this research, mixing behavior of the floating pollutant such as oil spill accidents was analyzed by studying the advection-diffusion of GPS floaters at water surface. The LPT (Lagrangian Particle Tracking) model of EFDC (Environmental Fluid Dynamics Computer Code) was used to simulate the motion of the GPS floater tracer. In the field experiment, 35 GPS floaters were injected at the Samun Bridge of Nakdong River. GPS floaters traveled to downstream about 700 m for 90 minutes. The field data by the GPS floater experiments were compared with the simulation in order to calibrate the parameter of LPT model. The turbulent diffusion coefficient of LPT model was determined as $K_H/hu^*$ = 0.17 from the scatter diagram. The arrival time of peak concentration and transverse diffusion from the simulation results were similar with the experiments from the concentration curves. Numerical experiments for anticipation of damage from floating pollutant were conducted in the same reach of the Nakdong River and the results show that the pollutant cloud transported to the left bank where the Hwawon pumping station is located. For this reason, it is suggested that the proper action should be needed to maintain the safety of the water withdrawal at the Hwawon pumping station.

• Steel and Composite Structures
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• v.28 no.4
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• pp.439-447
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• 2018

The structural behaviors of cylindrical barns as a specific engineering structure have been considered as a complicated computing process. The structure design against the earthquake load, to protect by using the code, is an urgency avoiding unexpected damages. The situation has been subjected to the applied design method if there would be no failure across the construction procedures. The purpose of the current study is to clarify the behaviors of cylindrical reinforced concrete barns through the analytic methods across the mass and Lagrangian approaches through the whole outcomes comparison indicating that the isoparametric element obtained from the Lagrangian approach has been successfully applied in the barns earthquake analysis when the slosh effects have been discarded. The form of stress distributions is equal with $s_z$ closed distributions to one another.

• 한국전산유체공학회:학술대회논문집
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• 2009.11a
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• pp.164-169
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• 2009

Study on swimming of microorganisms like, sperm motility, cilia beating, bacterial flagellar propulsion has found immense significance in the field of biological fluiddynamics. Because of the complexity involved, it is challenging for the researchers to model such problems. Immersed boundary method has proved its efficacy in the field of biological fluiddynamics, The present work aims at performing a numerical study on the microorganism locomotion using the immersed boundary method proposed by Peskin[1]. A two-dimensional model of the microorganism is modeled as thin elastic filament described as a sine wave. The neutrally buoyant organism undergoing deformations is immersed in a viscous and incompressible fluid. The fluid quantities are described using Eulerian coordinates and the immersed body is represented by Lagrangian coordinates. The Eulerian and Lagrangian variables are connected by the Dirac delta function. The Navier-Stokes equations governing the fluid flow are solved using the fractional step method on a staggered Cartesian grid system. The developed numerical code in FORTRAN will be validated by comparing the numerical results with the available results.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.11
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• pp.1538-1551
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• 1997

Kinetic energy conservation for fixed and moving grids is examined in time-accurate finite element computation of fully unsteady inviscid flows. As numerical algorithms, fractional step method (FSM) and modified SIMPLE are used. To simulate the flow in moving grid system, arbitrary Lagrangian-Eulerian (ALE) method is adopted. In the present study, the energy conserving time integration rule for finite element algorithm is proposed and discussed schematically. It is shown that the discretization by Crank-Nicolson in time and Galerkin (central difference) in space must be used to ensure energy conservation. The developed code has been tested for a standing vortex in fixed or moving grid system, sloshing in a tank and propagation of a solitary wave, and has been shown to be a completely energy conserving algorithm.

• Journal of the Society of Naval Architects of Korea
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• v.30 no.1
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• pp.145-156
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• 1993

An improved analysis model for material nonlinearity induced by elasto-plastic deformation and damage including large strain response was proposed. The elasto-plastic-damage constitutive model based on the continuum damage mechanics approach was adopted to overcome limitations of the conventional plastic theory, which can manage the anisotropic tonsorial damages evolved during time-independent plastic deformation process of materials. Updated Lagrangian finite element formulation for elasto-plastic damage coupling problem including large deformation, large rotation and large strain problems was completed to develop a numerical model which can predict all kinds of structural nonlinearities and damage rationally. Finally, a finite element analysis code for the 2-dimensional plane problem was developed and the applicability and validity of the numerical model was investigated through some numerial examples. Calculations showed reasonable results in both geometrical nonlinear problem due to large deformation and material nonlinearity including the damage effect.

• Journal of ILASS-Korea
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• v.9 no.4
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• pp.38-45
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• 2004

This study describes the analysis results of unsteady cavitating flows behavior inside nozzle of the prototype piezo-driven injector. This piezo-driven injector has been recognised as one of the next generation diesel injector due to a higher driven efficiency than the conventional solenoid-driven injector. The three dimensional geometry model along the central cross-section regarding of one injection hole has been used to simulate the cavitating flows for injection time by at fully transient simulation with cavitation model. The cavitation model incorporates many of the fundamental physical processes assumed to take place in cavitating flows. The simulations performed were both fully transient and 'pseudo' steady state, even if under steady state boundary conditions. We could analyze the effect the pressure drop to the sudden acceleration of fuel, which is due to the fastest response of needle, on the degree of cavitation existed in piezo-driven injector nozzle