• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1999.10a
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• pp.14-14
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• 1999

액체 램제트 엔진의 특성은 흡입구를 통해 들어오는 유입공기의 상태에 따라 많이 달라진다. 흡입구에 들어오는 공기의 유입각이 일정각도를 넘어서면 유입공기의 왜곡이 심하여 정상적인 연소가 불가능 할 수 있다. 따라서 다양한 비행조건에 따른 램제트 엔진의 특성을 파악하기 위하여 외부 유입영역, 흡입구, 연소기, 노즐 및 출구 대기 영역을 함께 계산하여 유동 특성과 연소 특성을 파악하고자 하였다. 흡입구는 마하 2.0을 기준으로 설계하고, 4각 덕트에서 완만하게 원형 덕트로 변화되는 확대관의 형상으로 비행체에 붙어 있는 것으로 격자를 구성하였다. 흡입구에서의 유동 조건은 비행체을 지난 유속이 마하 2.0과 2.2의 경우에 대하여 수치 실험을 수행하였으며, 비반응 유동 해석과 연소가 있는 반응 유동해석 결과를 흡입구를 포함하지 않았던 선행 연구 결과들과 비교하였다. 유입각이 영 일 때의 흡입구를 포함한 계산 결과는 흡입구에서 생성되는 충격파에 의한 손실로 총압력이 흡입구를 포함하지 않았던 선행 연구 결과와 차이가 있었으나 유동 특성에는 큰 차이가 없었다. 그러나 유입각이 증가함에 따라 흡입구로 유입되는 공기의 량이 감소하고 그에 따른 유동의 왜곡이 심하여 연소특성에 변화를 보여 주었다.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.3
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• pp.18-27
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• 2019

The flow mixing characteristics for the heated dual jets were numerically studied by using URANS (unsteady Reynolds-averaged Navier-Stokes). The increased turbulent diffusion was obtained for the compressible flow, and the thermal diffusion of incompressible flow increased more than that of compressible flow. From the results of FFT and phase portraits, periodic and quasi-periodic states were observed as the jet spacing increased. It was observed that linear variations of merging points and combined points were different because unsteady flow determined the flow mixing characteristics for a large jet spacing.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.04a
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• pp.588-593
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• 1997

본 연구에서는 이전의 연구들이 주로 정상상태의 공력만을 이용하여 소음을 예측하였으나 통상 팬은 단독으로 존재하지 않고 열교환기(radiator)와 같은 주의 물체와 함께 있으므로 이에 따르는 상호작용으로 인한 비정상 유동을 고려하여 소음을 예측하였다.

• Proceedings of the Korea Technology Innovation Society Conference
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• 2015.11a
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• pp.814-820
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• 2015

• Journal of the Korean Society of Propulsion Engineers
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• v.6 no.1
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• pp.1-11
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• 2002

The suitable turbulence model is found to be required in the course of establishing a proper analysis methodology for thermal stripping phenomena which are shown in strong temperature variation area such as reactors and propulsion devices. Three different turbulence models of $\kappa$-$\varepsilon$ model, modified $\kappa$-$\varepsilon$ model, and full Reynolds stress(FRS) model, are applied to analyze unsteady turbulent flows with temperature variation. Three test cases are selected for verification. These are vertical jet flows with water and sodium, and parallel jet flow with sodium. Analysis yields the conclusion that 3-D computation with FRS betters others. However, modified modeling is required to improve its heat transfer characteristic analysis. Further analysis is performed to find momentum variation effects on temperature distribution. It is found that the momentum increase results increase of fluid mixing and magnitude of temperature variation.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.877-880
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• 2017

Impeller blades in the centrifugal compressor are subjected to static loads due to the high-speed rotation and steady aerodynamic forces. At the same time, aerodynamic excitations by the interaction between the impeller and the diffuser vanes(DV) periodically excite the impeller blades in resonant conditions, which may lead to high cycle fatigue (HCF) and eventually result in failure of the blades. In order to predict the structural response accurately, the aerodynamic excitation and the major resonant conditions were predicted by performing the unsteady flow analysis and modal analysis using ANSYS. Next, a unidirectional forced vibration analysis was performed by using fluid-structure interaction (FSI) method, and the safety of HCF was evaluated based on the results.

• Proceeding of EDISON Challenge
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• 2012.04a
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• pp.105-108
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• 2012

이차원 단면 Cylinder는 외부유동상태에서 후류에 Vortex를 생성한다. 또한 비정상 유동 상태에서는 후류에 카르만 Vortex열을 생성한다. 이런 이차원 Cylinder는 여러 분야에서 사용 된다. 이때 적절한 설계를 위해 수치적으로 유동을 해석할 필요가 있다. 이에 대한 수치적 해석 값을 얻기 위해 Edison CFD를 이용하여 여러 2차원 형상 Cylinder의 Reynolds number에 따른 Vortex shedding을 해석했다. Edison CFD를 통한 시뮬레이션 결과 값에 대한 검증을 얻기 위해 원형, 사각형의 Vortex shedding과 유동을 타 논문과 비교 검증했다. 형상마다 같은 조건의 Reynolds number라도 후류와 유동 등의 형상이 차이를 보인다. 상황마다 적절한 모형의 Cylinder를 Edison CFD를 통해 예측 할 수 있다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.8 no.3
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• pp.256-267
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• 1996

In estuarine 3-dimensional numerical modeling. it is very important to calculate vertical eddy viscosity accurately. Various turbulence models employing eddy viscosity concept were applied to the steady flow in an open-channel and the tidal flow in long tidal channel and compared. The evaluations include the verification tests against experimental data sets for steady and tidal flows. The simulation results have shown that the compared models are in good agreements with experimental data of steady flow while only $textsc{k}$-$\varepsilon$ model, $textsc{k}$-ι model, and 1-equation model with well-defined mixing length profile give good agreements with experimental data of tidal flow.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.12
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• pp.1153-1161
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• 2010

An efficient solution method for harmonic balance techniques with Fourier transform is presented for periodic unsteady flow problems. The present partially-implicit harmonic balance treats the flux terms implicitly and the harmonic source term is solved explicitly. The convergence of the partially Implicit method is much faster than the explicit Runge-Kutta harmonic balance method. The method does not need to compute the additional flux Jacobian matrix from the implicit harmonic source term. Compared with fully implicit harmonic balance method, this partial approach turns out to have good convergence property. Oscillating flows over NACA0012 airfoil are considered to verify the method and to compare with results of explicit R-K(Runge-Kutta) and dual time stepping methods.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.81.2-81.2
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• 2005