• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.633-640
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• 2007

In this paper, 3-D reciprocating compressor is taken into flow-structure interaction analysis. The full cycle process consisted of cylinder expansion and compression has been modeled without considering flow leakage through cylinder wall. Fully-coupled FSI analysis of this compressor model was iteratively solved and gives sufficient result with the experimental test. The study is emphasized to thoroughly investigate discharge valve motion, opening and closing, in order to determine discharge valve region which is prone to have high effective stress. The cylinder pressure is successfully validated before conducting impact analyses between discharge valve and other susceptible supported structure. Velocity profile has been obtained in FSI analysis is used as initial condition to carry out further impact analyses. Stress result of discharge valve and valve spring gives preliminary estimation of higher stress area due to its impact phenomena.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.542-545
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• 2009

In this study, the effect of turbine geometry on the overall performance of a gas turbine was investigated by computational fluid dynamics. Overall engine performance was predicted through a full engine simulation program which can predict the interactions of the compressor, the combustor and the turbine. The compressor and the turbine analysis code solves 2D and 3D Navier-Stokes equations respectively. The chemical equilibrium code was applied to simulate the combustor. The computations were performed for two different shapes of turbine nozzle. The nozzle shapes adopted a baseline blade and a blade with fillet.

• Journal of computational fluids engineering
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• v.21 no.3
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• pp.48-54
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• 2016

In the present work, numerical simulations were conducted on the scaled model of the BWB type UCAV in the subsonic region using ANSYS FLUENT V15. The prediction method was validated through comparison with experimental results and the effect of the twisted wing was investigated. To consider the transitional flow phenomenon, ${\gamma}$ transition model based on SST model was adopted. The coefficients of lift, drag and pitching moment were compared with experimental results and the pressure distribution and streamlines were investigated. The twisted wing decreases the lift force but increases lift-to-drag ratio through delay of stall and leading edge vortex's movement to the front, also the non-linearity of the pitching moment is decreased.

• Journal of computational fluids engineering
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• v.19 no.2
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• pp.58-65
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• 2014

The adaptive wavelet method is studied for the enhancement of computational efficiency of three-dimensional flows. For implementation of the method for three-dimensional Euler equation, wavelet decomposition process is introduced based on the previous two-dimensional adaptive wavelet method. The order of numerical accuracy of an original solver is preserved by applying modified thresholding value. In order to assess the efficiency of the proposed algorithm, the method is applied to the computation of flow field around ONERA-M6 wing in transonic regime with 4th and 6th order interpolating polynomial respectively. Through the application, it is confirmed that the three-dimensional adaptive wavelet method can reduce the computational time while conserving the numerical accuracy of an original solver.

• Journal of the Korean institute of surface engineering
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• v.41 no.4
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• pp.134-141
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• 2008

We have developed a numerical model for a remote ICP(inductively coupled plasma) system in 2D and 3D with gas distribution configurations and confirmed it by plasma diagnostics. The ICP source has a Cu tube antenna wound along a quartz tube driven by a variable frequency rf power source($1.9{\sim}3.2$ MHz) for fast tuning without resort to motor driven variable capacitors. We investigated what conditions should be met to make the plasma remotely localized within the quartz tube region without charged particles' diffusing down to a substrate which is 300 mm below the source, using the numerical model. OES(optical emission spectroscopy), Langmuir probe measurements, and thermocouple measurement were used to verify it. To maintain ion current density at the substrate less than 0.1 $mA/cm^2$, two requirements were found to be necessary; higher gas pressure than 100 mTorr and smaller rf power than 1 kW for Ar.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.519-522
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• 2010

Flow-induced vibration analyses have been conducted for a 3D compressor blade model. Advanced computational analysis system based on computational fluid dynamics(CFD) and computational structural dynamics has been developed in order to investigate detailed dynamic responses of designed compressor blades. A fully implicit time marching scheme based on the Newmark direct integration method is used for computing the coupled aeroelastic governing equations of the 3D compressor blade for fluid-structure interaction problems. Detailed dynamic responses and instantaneous pressure contours on the blade surfaces considering flow-separation effects are presented to show the multi-physical phenomenon of the rotating compressor blade.

• International Journal of Fluid Machinery and Systems
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• v.3 no.1
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• pp.20-28
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• 2010

This paper deals with the Design and Analysis of a Controlled Diffusion Aerofoil (CDA) Blade Section for an Axial Compressor Stator and Effect of incidence angle and Mach No. on Performance of CDA. CD blade section has been designed at Axial Flow Compressor Research Lab, Propulsion Division of National Aerospace Laboratories (NAL), Bangalore, as per geometric procedure specified in the U.S. patent (4). The CFD analysis has been performed by a 2-D Euler code (Denton's code), which gives surface Mach No. distribution on the profiles. Boundary layer computations were performed by a 2-D boundary layer code (NALSOF0801) available in the SOFFTS library of NAL. The effect of variation of Mach no. was performed using fluent. The surface Mach no. distribution on the CD profile clearly indicates lower peak Mach no. than MCA profile. Further, boundary layer parameters on CD aerofoil at respective incidences have lower values than corresponding MCA blade profile. Total pressure loss on CD aerofoil for the same incidence range is lower than MCA blade profile.

• International Journal of Automotive Technology
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• v.8 no.5
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• pp.659-666
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• 2007

In the present study, a numerical analysis of the three-dimensional heat transfer and fluid flow for a vehicle cooling system was developed. The flow field of the engine room between the grille and radiator was analyzed. The results show that, as the airflow inlet grille angle $\alpha$ is varied from $15^{\circ}$ to $-15^{\circ}$, the air flow rate compared with $\alpha=0^{\circ}$(horizontal) changes from -11.9% to +5.1%; while the heat flux from the radiator changes from -9.2% to +4.4%. When the airflow inlet bumper angle $\beta$ is varied from $-5^{\circ}$ to $+15^{\circ}$, the heat flux from the radiator compared with $\beta=0^{\circ}$(horizontal) increases up to +4.4%. When the airflow inlet grille angle $\alpha=-15^{\circ}$ and the bumper grill angle $\beta=+15^{\circ}$, the airflow rates and heat flux compared with($\alpha=0^{\circ}$, $\beta=0^{\circ}$) can be increased to +9.5% and +7.5%, respectively. The results indicate that the optimal angles for cooling efficiency are used.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.345-349
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• 2016

보본체와 물받이공을 보호하는 바닥보호공(bed protection)은 굴요성 구조(flexible structure)인 돌망태, 블록공, 사석 등으로 설치되어야 하며, 일반적으로 경제성과 시공성이 우수한 사석(riprap)이 많이 이용된다. 이때 사석의 안정성 확보를 위한 설계기준으로 국내의 경우 포설길이에 대해서만 제시하고 있으나, 외국의 경우 수심, 유속 등의 값을 기초로 사석의 크기, 포설두께, 포설길이를 산정할 수 있도록 상세하게 제시하고 있다. 이와 같은 실정으로 국내 하천 실무자들이 바닥보호공을 설계 할 때 하천설계기준을 바탕으로 블라이 공식 또는 국립건설시험소 공식을 적용하여 사석의 포설길이는 산정하지만 사석의 크기, 중량 등의 제원들은 외국 설계기준을 차용하여 산정하거나 생략하는 경우도 있다. 따라서 하천설계기준의 보완 및 최근 국내 주요하천에서 발생하는 바닥보호공 유실, 침하 등의 문제를 해결하기 위한 연구가 필요하다. 본 연구는 전산유체동역학(Computational Fluid Dynamics, CFD) 모형인 FLOW-3D 모형을 이용하여, 바닥보호공 주변 흐름에 대한 수치모의를 수행하였다. 이때 난류 모형은 LES (Large Eddy Simulation) 모형을 적용하였으며, 바닥보호공에 작용하는 비교적 작은 척도의 와(vortex)를 해상할 수 있도록 조밀한 격자를 부여하였다. 초기 수치모형 결과의 적정성은 수리실험 결과와 비교하여 판단하였으며, 수리실험을 잘 재현해내는 격자, 매개변수 등을 적용하여 보의 하류 수위 변화에 따른 유속, 난류강도 등에 대한 분석을 수행하였다. 본 연구 결과는 바닥보호공 설계를 위한 기초자료로 활용될 수 있으며, 향후 수리실험과 병행하여 국내 실정에 맞는 설계식 개발에 대한 연구가 필요한 것으로 보인다.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.308-308
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• 2017

국내 하천에 설치된 횡단구조물은 2009년을 기준으로 약 20,753개로 알려져 있으며 수위 유지, 하상고 유지 등의 목적을 가지고 설치된다. 그러나 낙차를 가진 빠른 유속의 흐름을 형성시켜, 하류 하상에서 국소 세굴을 발생시킨다. 이를 방지하기 위해 횡단구조물 하류에 굴요성 구조(flexible structure)인 돌망태, 블록공, 사석 등으로 이루어진 바닥보호공(bed protection)이 설치되나 유실, 침하 등의 문제가 빈번히 발생되고 있어, 문제를 해결하기 위한 연구가 필요하다. 본 연구는 이러한 피복 대책에서 일어날 수 있는 파괴 기구인 전단파괴, 흡출 파괴, 경계 파괴, 하상 형태 변화에 따른 하부 침식 중 흡출 파괴(winnowing failure)를 유발하는 흐름을 검토하기 위한 수치모의를 수행하였다. 이때 흡출 파괴는 바닥보호공의 공극으로 미세한 하상 재료가 난류와 침투류의 작용에 의해 침식되어 바닥보호공이 침하되는 것을 말한다. 수치모의는 전산유체동역학(Computational Fluid Dynamics, CFD) 모형인 FLOW-3D 모형을 이용하였으며, 난류 모형으로 LES 모형을 적용하고 조밀한 격자를 부여하여 바닥보호공의 공극에서 발생되는 비교적 작은 척도의 와(vortex)를 해상할 수 있도록 하였다. 수치모의에 적용된 횡단구조물은 보, 물받이공, 바닥보호공으로 구성하였으며 특히, 바닥보호공의 형상은 구체(sphere)로 가정하여 다층으로 배치하였다. 바닥보호공의 공극 또는 구체 사이에서 발생되는 유속, 압력 등의 흐름특성을 분석한 결과, 바닥보호공 두께가 두꺼울수록 흡출 파괴에 대해 안정적인 것으로 나타났다. 이는 바닥보호공 설계를 위한 기초자료로 활용될 수 있으며, 향후 입자영상유속계(Particle Image Velocimeter, PIV)와 같이 공극에서 흐름을 측정할 수 있는 방법과 병행한 연구를 수행할 수 있을 것이다.