• 한국전산유체공학회:학술대회논문집
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• 2003.08a
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• pp.69-75
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• 2003

본 연구에서는 격자 생성, 초기유동조건 및 경계조건 설정 등 일련의 전처리 과정을 사용자에게 친숙한 그래픽 인터페이스 환경으로 개발하였다. MFC/Visual C++를 이용하여 개발된 전처리 프로그램은 Windows 계열의 OS와 호환이 가능하며, 기하학적 격자생성, 초기값 설정 및 수치해석 코드의 제어변수를 생성할 수 있다. 한편 사용자의 편의를 위해서 전처리 과정을 격자생성(단일격자생성, 다중격자생성), 유체 물성치정의, 경계조건 생성, 초기조건 생성 및 코드제어로 구분하였다. 개발된 전처리 프로그램의 특성으로서 다중 격자 생성 작업을 단일 격자계의 중첩으로 구성될 수 있도록 각 경계면을 "interface"형을 취하는 기능을 제공하도록 하였으며 개발된 전처리 과정을 16도의 경사면을 가지는 Compression ramp 문제 및 축대칭 Bump 문제에 적용하여 개발된 전처리 과정을 검증하였다.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.282-287
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• 2001

The CSCM Upwind method and Material Transport Analysis (MTA) have been used to predict the thermal response and ablation rate for non-charring material to be used as thermal protection material (TPM) in KSR-III test rocket nozzle. The thermal boundary conditions such as cold wall heat-transfer rate and recovery enthalpy for MTA code are obtained from the upwind Navier-Stokes solution procedure. The heat transfer rate and temperature variations at rocket nozzle wall were studied with shape change of the nozzle surface as time goes by. The surface recession was severely occurred at nozzle throat and this affected nozzle performance such as thrust coefficient substantially.

• Journal of the Korea Institute of Military Science and Technology
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• v.5 no.4
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• pp.88-96
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• 2002

The CSCM Upwind method and Material Transport Analysis(MTA) have been used to predict the thermal response and shape changes for charring/non-charring material which can be used as thermal protection material(TPM) on blunt-body nose tip. We performed intensive flight trajectory simulations to compare 1-D MTA results with those of 2-D/Axisymmetric MTA by using MTAs and Navier-Stokes code. Theheat-transfer rate and pressure distribution were predicted at selected altitudes and wall temperature along the flight trajectory and the shape changes of blunt-body nose tip were predicted subsequently by using current procedure.

• 한국전산유체공학회:학술대회논문집
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• 2003.08a
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• pp.76-81
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• 2003

전산유체공학에서 그래픽 인터페이스를 이용한 후처리 기법은 수렴된 해의 물리적 구조 및 특성을 이해하는데 있어 매우 중요하다. 따라서 본 연구에서는 그래픽 환경을 이용하여 압축성 유동 해석 코드인 CSCM 수치해석 코드의 후처리 과정을 개발함으로서 코드전체의 완전성을 높이고자 하였다. Visual C++프로그램을 이용하여 Mesh plot, XY plot, 벡터 plot 및 contour plot이 가능한 후처리 프로그램을 개발하였으며 실시간으로 수치해석의 수렴정도를 파악할 수 있는 잔류항에 대한 그래픽 기능을 제공하게 하였다. 개발된 후처리 과정을 2차원 Compression ramp 및 Bump 문제의 해석결과에 대해 본 연구결과와 현재 유체해석의 후처리 프로그램으로 많은 사용자를 확보하고 있는 AMTEC사의 Tecplot 8.0 버전의 결과를 서로 비교해 본 결과 좋은 일치성을 보여주었다.

• 한국전산유체공학회:학술대회논문집
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• 2004.10a
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• pp.121-125
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• 2004

The preprocessor - solver - postprocessor software for 2D/Axisymmetric CSCM Upwind Flux Difference Splitting Navier-Stokes code has been developed for undergraduate educational purpose. This computational fluid dynamics (CFD) software allows students to setup, solve, visualize and control dynamically server for their own fluid problems via Internet. The preprocessor Is capable of generating geometry and grid, initial solution data and required solver control parameters. The postprocessor shows vector plot and contour plot with different options while residual plot shows root-mean-square (RMS) error history graphically and retrieves the data from solver interactively. Special feature of the preprocessor is grid generation part which is based on MFC/Visual C++ application and FORTRAN single block grid generator process. Many users can access solver via Internet from client computers and solve desired problems using locally installed pre- and postprocessor and remote powerful solver part.

• 한국전산유체공학회:학술대회논문집
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• 1999.11a
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• pp.17-22
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• 1999

Convergence characteristics and efficiency of three implicit approximate factorization schemes(ADI, DDADI and MAF) are examined using 2-Dimensional compressible upwind Navier-Stokes code. Second-order CSCM(Conservative Supra Characteristic Method) upwind flux difference splitting method with Fromm scheme is used for the right-hand side residual evaluation, while generally first-order upwind differencing is used for the implicit operator on the left-hand side. Convergence studies are performed using an example of the flow past a NACA0012 airfoil at steady transonic flow condition, i. e. Mach number 0.8 at $1.25^{\circ}$ angle of attack. The results were compared with other computational results in order to validate the current numerical analysis. The results from the implicit AF algorithms were compared well in low surface with the other computational results; however, not well in upper surface. It might be due to lack of the grid around the shock position. Because the algorithm minimizes the errors of the approximate decomposition, the improved convergence rate with MAF were observed.

• Journal of Mechanical Science and Technology
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• v.18 no.1
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• pp.153-166
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• 2004

This paper presents a comparative study of a fully coupled, upwind, compressible Navier-Stokes code with three two-equation models and the Baldwin-Lomax algebraic model in predicting transonic/supersonic flow. The k-$\varepsilon$ turbulence model of Abe performed well in predicting the pressure distributions and the velocity profiles near the flow separation over the axisymmetric bump, even though there were some discrepancies with the experimental data in the shear-stress distributions. Additionally, it is noted that this model has y$\^$*/ in damping functions instead of y$\^$＋/. The turbulence model of Abe and Wilcox showed better agreements in skin friction coefficient distribution with the experimental data than the other models did for a supersonic compression ramp problem. Wilcox's model seems to be more reliable than the other models in terms of numerical stability. The two-equation models revealed that the redevelopment of the boundary layer was somewhat slow downstream of the reattachment portion.

• 유체기계공업학회:학술대회논문집
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• 1999.12a
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• pp.134-140
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• 1999

A three-dimensional CSCM upwind flux difference splitting Navier-stokes code with two-equation turbulence models was developed to predict the transonic flows in centrifugal compressor diffuser. The k-$\epsilon$ model of Abe et al. performed well in predicting the pressure distribution in the shock wave/turbulent boundary-layer interaction. Three turbulence models predicted the similar distribution of static pressure through the diffuser and showed a good agreement with the experimental results. The secondary flows in the corner were predicted well by these turbulence models. The pressure increase before the throat of the diffuser vane is important for the overall pressure recovery. As the mass flow rate increased the blockage decreased at the throat. The pressure coefficient distribution through the diffuser depended on the throat blockage not on the rotational speed of the impeller.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.5
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• pp.333-340
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• 2019

Tests using a middle velocity propulsion impact machine (MVPIM) were performed to verify the impact resistance capability of sandwich concrete panels (SCP) in a modular liquefied natural gas (LNG) outer tank, and numerical models were constructed and analyzed. $2{\times}2m$ specimens with plain sectional characteristics and specimens including a joint section were used. A 51 kg missile was accelerated above 45 m/s and impacted to have the design code kinetic energy. Impact tests were performed twice according to the design code and once for the doubled impact speed. The numerical models for simulating impact behaviors were created by LS-DYNA. The external steel plate and filled concrete of the panel were modeled as solid elements, the studs as beam elements, and the steel plates as elasto-plastic material with fractures; the CSCM material model was used for concrete. The front plate deformations demonstrated good agreement with those of other tests. However the rear plate deformations were less. In the doubled speed test for the plain section specimen, the missile punctured both plates; however, the front plate was only fractured in the numerical analysis. The impact energy of the missile was transferred to the filled concrete in the numerical analysis.