• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2007년도 제28회 춘계학술대회논문집
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• pp.329-334
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• 2007

초음속 제트 마하수 1.07부터 1.2 범위에서 축대칭 제트 스크리치 톤을 해석하였다. 축대칭 모드는 낮은 마하수 축대칭 제트의 지배적인 스크리치 톤 모드이다. 난류 해석을 위해 수정된 Spalart-Allmaras 모델을 RANS (Reynolds-averaged Navier-Stokes) 방정식에 사용하였다. 스크리치 톤 해석에서 중요한 음파의 전파, shock-cell 구조, shock-cell의 비정상 거동 및 거대한 불안정 파를 정확히 계산하기 위해 비반사 특성 경계조건과 연계한 고차정확도의 ENO 기법을 사용하였다. 수치해석결과는 다른 연구자들의 실험 결과와 잘 일치하였으며, 따라서 본 연구에 사용된 수치 기법들이 초음속 제트 유동 구조 및 소음연구에 유용함을 확인하였다.

• 한국전산유체공학회지
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• 제9권4호
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• pp.41-47
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• 2004

The paper presents numerical simulations of laminar vortex-shedding flows past a circular cylinder for Re ≤ 500. The simulations are performed by solving the unsteady 2-D Navier-Stokes equations with a finite volume method using unstructured grid system. The resulting Reynolds number dependence of the Strouhal number and of the drag and lift coefficients is compared with experiments and with previous numerical results, showing good agreement. It is found that, for the truly laminar Reynolds number range the present calculation method described is capable of producing reasonably accurate results for the main practically relevant parameters such as Strouhal number, drag and lift coefficients.

• 한국전산유체공학회지
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• 제10권4호통권31호
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• pp.24-31
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• 2005

A dynamic simulation on the missile staging system is conducted with numerical techniques. Both Euler equations and Navier-Stokes equations are numerically solved respectively. The dynamic simulation of two moving bodies is fully integrated into the computational fluid dynamics solution procedure. The Chimera grid scheme is applied in this simulation for unsteady supersonic flow analysis with dynamic modeling. The objective of the study is to investigate the problem pertaining to possible unstability in missile staging. In addition, the computational comparison between in viscid and viscid flow solvers is also performed in this study.

• The Journal of the Acoustical Society of Korea
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• 제20권4E호
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• pp.17-23
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• 2001

To develop the code of predicting flow-field and aeroacoustic noise by an electrical cable, a combined CFD-Acoustic analogy approach is selected. The two dimensional, unsteady and incompressible Reynolds-averaged Navier-Stokes solver with κ-ω and κ-ω SST turbulence modeling is used to calculate the near flow-field around an electric cable. Near-field results are then coupled with two-dimensional Curle's integral formulation based upon Lighthill's acoustic analogy with the assumption of acoustic compactness. To validate this code, numerical results are compared with experimental data for a circular cylinder. The simulation shows an overprediction on acoustic amplitudes, but overally speaking, the spectrum pattern of sound pressure agrees well with experiment within an acceptable amount of error. In addition, a few cross-sections of the cable were selected and tested with each other in terms of drag and radiated noise

• 대한기계학회논문집B
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• 제24권6호
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• pp.777-784
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• 2000

A Navier-Stokes code based on an unstructured finite volume method is used to simulate the MIT flapping foil experiment. A low Reynolds number ${\kappa}-{\varepsilon}$ turbulence model is used to close the Reynolds averaged Navier-Stokes equations. Computations are carried out for the whole experimental domain involving two flapping foils and a downstream hydrofoil. The computational domain is meshed with unstructured quadrilateral elements, partly structured. Numerical solutions show good agreement with experiment. The first harmonics of the velocity in the boundary layer shows local peak value inside the boundary layer and also local minimum near the edge of boundary layer. It is intensified as it develops along the blade surface. This is shown to be caused as the unsteadiness inside the boundary layer is being convected at a speed less than the free stream value. It is also shown that there is negligible mixing of the unsteadiness between the boundary layer and the free stream.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 1999년도 유체기계 연구개발 발표회 논문집
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• pp.163-169
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• 1999

The numerical procedure has been developed for simulating incompressible viscous flow around a turbine stage with rotor-stator interaction. This study solves 2-D unsteady incompressible Navier-Stokes equations on a non-orthogonal curvilinear coordinate system. The Marker-and-Cell concept is applied to efficiently solve continuity equation. To impose an accurate boundary condition, O-H multiblocked grid system is generated. O-type grid and H-type grid is generated near and outer rotor-stator The cubic-spline interpolation is applied to handle a relative motion of a rotor to the stator. Turbulent flows have been modeled by the Baldwin- Lomax turbulent model. To validate present procedure, the time averaged pressure coefficients around the rotor and stator are compared with experiment and a good agreement obtained.

• 대한조선학회논문집
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• 제40권5호
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• pp.36-42
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• 2003

A CFD simulation technique has been developed to handle the unsteady body motion with large amplitude by use of overlapping multi-block grid system. The three-dimensional, viscous and incompressible flow around body is investigated by solving the Navier-Stokes equations, and the motion of body is represented by moving effect of the grid system. Composite grid system is employed in order to deal with both the body motion with large amplitude and the condition of numerical wave maker in convenience at the same time. The governing equations, Navier-Stokes (N-S) and continuity equations, are discretized by a finite volume method, in the framework of an O-H type boundary-fitted grid system (inner grid system including test model) and a rectangular grid system (outer grid system including simulation equipments for generation of wave environments). If this study, several flow configurations, such as an oscillating cylinder with large KC number, are studied in order to predict and evaluate the hydrodynamic forces. Furthermore, the motion simulation of a Series 60 model advancing in a uniform flow under the condition of enforced roll motion of angle 20$^{\circ}$ is performed in the developed numerical wave tank.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2001년도 춘계 학술대회논문집
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• pp.121-126
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• 2001

An accelerating flow field through a compressor cascade is studied numerically by unsteady computational simulation. The two-dimensional Navier-Stokes equations for compressible flow is used for the study of unsteady high incidence angle flow, with preconditioning scheme to cover the wide range of Mach number and $\kappa-\omega$ model for the turbulent viscous flow analysis. A DCA(double circular arc) compressor blade is accelerated artificially in this study to understand the unsteady effect by comparing the present results with the existing steady-state experimental and computational results. Also, the accelerating flow field during the starting phase of gas turbine is studied with actual experimental data for the understanding of flow field and performance characteristics at off-design condition.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.415-421
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• 2006

The unsteady flow calculation around the proprotor of Smart UAV was conducted. Using the flight scenario of SUAV which composed of hover, transition, and airplane mode, the aerodynamic analysis of proprotor were performed for the variation of collective pitch, rpm, forward speed, and tilt angle. The unsteady compressible Navier-Stokes equations were used for the calculation and the dynamic overset grid technique was applied for the rotating proprotor. The aerodynamic performance of proprotor calculated in this way were validated by comparing with the performance data obtained from the blade element momentum method.

• 한국화재소방학회논문지
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• 제29권5호
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• pp.42-50
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• 2015

도심지역을 단순 모델링한 실규모 공간에서 누출된 프로판 확산과정에 대해 대와동모사(Large Eddy Simulation: LES), 분리와동모사(Detached Eddy Simulation: DES) 및 비정상 레이놀즈평균기법(Reynolds Averaged Navier-Stokes: RANS)을 이용한 3가지 전산해석을 수행하였다. 전산해석은 FLUENT 14를 이용하였고 격자계는 ICEM-CFD를 이용하여 구성하였다. 그 결과 건물 주변의 프로판 농도분포는 주변 와구조와 밀접한 관련이 있어 이러한 와구조를 합리적으로 예측하는 정도에 따라 농도분포가 크게 차이날 수 있음을 알았다. LES와 DES는 비교적 유사한 와구조와 프로판 농도분포를 보이지만 RANS는 너무 부드러운 농도분포를 보여 복잡한 비정상적인(Unstedy) 난류 유동장을 재현하는데 한계가 있어 가스연료 누출 초기의 농도분포 전개과정을 예측하는 데에는 어려움이 있을 것으로 판단된다. 해석결과와 계산시간까지 고려한다면 DES 방법이 실규모에서의 가스연료 누출 확산과정에 대한 CFD 해석방법으로 적합할 것으로 판단된다.