• 한국전산유체공학회지
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• 제19권1호
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• pp.27-33
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• 2014

A new and efficient implicit scheme is proposed to obtain a steady-state solution in time integration and the comparison of characteristics with the approximation ways for the implicit method to solve the incompressible Navier-Stokes equations is provided. The conservative, finite-volume cell-vertex upwind scheme and artificial compressibility method using dual time stepping for time accuracy is applied in this paper. The numerical results obtained indicate that the direct application of Jacobian matrix to the Lower and upper sweeps of implicit LU-SGS leads to better performance as well as convergence regardless of CFL number and true time step than explicit scheme and approximation of Jacobian matrix. The flow simulation around box in uniform flow with unstructured meshes is demonstrated to check the validity of the current formulation.

• 한국전산유체공학회지
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• 제18권1호
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• pp.13-21
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• 2013

Cavitating flow is usually formed on the surface of a high speed underwater object. When a object moves near a free surface at very high speed, the cavity signature becomes one of the major factors to be overcome by sensors of military satellite. The present work was to study the free surface effect on the ventilated cavitation. The governing equations were Navier-Stokes equations based on a homogeneous mixture model. The multiphase flow solver used an implicit preconditioning method in the curvilinear coordinate system. The cavitation model used here was the one first presented by Merkle et al.(2006) and redeveloped by Park & Ha(2009). Computations considered the free surface effects were carried out with a NACA0012 hydrofoil and the corresponding results were compared with the experimental data to have a good agreement. Calculations were then performed considering the ventilated cavitation, including the effect of non-condensable gas under the free surface effects.

• 한국항공우주학회지
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• 제33권9호
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• pp.34-40
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• 2005

본 연구에서는 비정상 유동해석을 위한 CFD 코드의 개발을 위해 대각화 ADI 기법을 적용한 정상 해석기법과 내재적 이중시간 전진기법을 도입하였다. 정상상태 Navier-Stokes 방정식의 Jacobian 행렬은 비점성항에 대해서만 적용하였고 여기에 내재적 인공점성 연산자를 첨가하여 블록 5대각 행렬을 유도하였다. 시간단축을 위해 스칼라 5대각 행렬로 대체하였다. 가상시간에 대한 정상상태기법에 실시간에 대한 미분항이 포함된 새로운 잔류항을 정의하였다. 가상시간에 대해 수렴된 해로부터 실시간 해를 구하고 시간에 대해 적분을 수행하는 내재적 이중시간 전진기법을 이용한 비정상 Navier-Stokes 코드를 개발하였다. 이에 대한 검증으로 정지한 유체속에 진동하는 평판문제, 원기둥 후방의 주기적인 Karman 와류생성, 이중원호 익형주위의 충격파 진동문제등을 수치해석하여 이론치, 실험치, 타연구자의 계산결과와 비교, 분석하였다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2001년도 춘계 학술대회논문집
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• pp.127-133
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• 2001

In this paper, the preconditioned multistage time stepping methods which are popular multigrid smoothers is studied for the compressible flow calculations. Fourier analysis on the local time stepping and block-Jacobi preconditioned residual operators is performed using the linearized 2-D Navier-Stokes equations. It fumed out that block-Jacobi preconditioner has better performance in eigenvalue clustering. They are implemented in the 2-D compressible Euler and Wavier-Stokes calculations with multigrid methods to verify that the block-Jacobi preconditioned multistage time stepping shows better performance in convergence acceleration.

• 한국전산유체공학회지
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• 제8권4호
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• pp.1-5
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• 2003

A Thin-layer Wavier-Stokes equations are applied for the hypersonic flow over blunt bodies with applications to laminar as well as turbulent flows. The equations are expressed in the forms of flux-vector splitting and explicit algorithm. The upwind schemes of Steger-Warming and Van Leer are investigated to predict accurately the heating loads along the surface of the body. A mixed scheme has been presented for the differencing the convective terms and the mixed scheme is found to be less dissipative producing accurate solutions.

• 한국HCI학회:학술대회논문집
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• 한국HCI학회 2009년도 학술대회
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• pp.463-468
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• 2009

본 논문은 데스크탑 PC 에서만 구현 가능하였던 기존의 유체 시뮬레이션 기술을 모바일 환경으로 확장하는 방법론을 제시한다. 유체 시뮬레이션은 나비어-스토크스 (Navier-Stokes) 방정식의 수치적 해를 구하는 것이며, 기존의 방법론은 수치적 해의 안정성과 [1] 사실성 [2]에 그 초점을 맞추고 있다. 하지만 이는 모바일 기기에서 기대하기 힘든 충분한 연산 자원을 가정한 것이다. 한편, 모바일 환경에서의 물리기반 기술은 현재 강체 시뮬레이션 모듈이 주로 활용되고 있으며 [3], 유체 시뮬레이션은 높이장 (Height field) 기반의 단순한 모델만이 제시되어있다 [4]. 이를 극복하기 위해 본 연구에서는 이러한 한계를 극복한 수정된 비압축유동의 시뮬레이션 기법을 소개하며, 또한 모바일 상에서 유체의 가시화 기술을 제안한다.

• 조명전기설비학회논문지
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• 제22권12호
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• pp.130-141
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• 2008

본 논문에서는 원통형 선형유도전동기를 이용한 순환식 유동시스템에서의 유체특성을 해석하였다. 먼저 유동시스템에 필요한 추력 40[N] 원통형 선형유도전동기를 등가회로법과 유전알고리즘을 이용하여 설계하였다. 이 힘이 유체시스템에 작용하는 경우 유체의 특성은 유체방정식과 전자기 방정식을 결합하여 해석하여야 한다. 본 논문에서는 유체의 속도에 따라 층류해석과 난류해석이 가능한 해석프로그램을 개발하고, 각각에 대한 유충특성 해석을 하였다. 또한 전자기력에 의한 추력이 시스템에 추가되었을 때의 특성을 분석하였다.

• 한국전산유체공학회지
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• 제13권2호
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• pp.20-26
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• 2008

A numerical study is carried out to analyze the steady three-dimensional turbulent flow and convective heat transfer in a staggered pin-fin array with diamond shaped elements at various geometrical configurations. Steady Reynolds-averaged Navier-Stokes equations and energy equation are solved using a finite volume based solver. Shear stress transport (SST) model is used as turbulence closure. The computational domain is composed of one pitch of pin-fin displacement with periodic boundary conditions on the surfaces normal to the streamwise direction and the cross-streamwise direction. The numerical results for Nusselt number and friction factor are validated with experimental results. The effects of pin angle, pin height and pitch on Nusselt number, friction factor and efficiency index are investigated.

• 한국전산유체공학회지
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• 제16권2호
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• pp.11-16
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• 2011

Numerical analyses have been carried out to analyze the three-dimensional turbulent heat transfer by impingement jet on a concave surface with variation of geometric configurations. Three-dimensional Reynolds averaged Navier-stokes equations have been calculated using the shear stress transport turbulent model. The numerical results for heat transfer rate were validated in comparison with the experimental data. The distance between jet nozzles and angle of inclined jet nozzle were selected as the geometric variables. Area-averaged Nusselt numbers on concave surface are evaluated to find the characteristics of heat transfer with the two geometric variables. The heat transfer increases as the distance between jet nozzles increases, and the inclined impinging jets show much better heat transfer performance than the vertical impinging jet.

• 한국유체기계학회 논문집
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• 제15권4호
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• pp.19-26
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• 2012

In this paper, a parametric study on ribs which are installed in an equilateral triangular internal cooling channel is presented. The numerical analysis of the flow structure and heat transfer characteristics is performed using three-dimensional Reynolds-averaged Navier-Stokes equations with the shear stress transport turbulence model. The numerical results are obtained at Reynolds number, 20,000. The parametric study is performed for the parameters, the angle of a rib, rib pitch-to-hydraulic diameter ratio, rib width-to-hydraulic diameter ratio, and rib height-to-hydraulic diameter ratio. The computational results are validated with the experimental data for area-averaged Nusselt number.