• 수산해양기술연구
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• 제37권1호
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• pp.1-8
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• 2001

This study deals with the experimental and numerical investigations to design the high performance otter board. Experiment was carried out to determine the most effective slot size of single-slot cambered otter board in the circulation water channel of BAEK KYUNG IND. Co. LTD. Numerical analysis was done by the commercial CFD code, FLUENT, to provide some valuable physical interpretations and finally to design the otter board section by numerical method. The major results are as follows ; 1. In experiment, the maximum lift and drag coefficients of simple cambered type otterboard were 1.41, 0.55, respectively, at the angle of attack $28^\circ$, while those of slot one with slot size 0.02C (C denotes the chord length) were 1.72, 0.42 at the angle of attack $24^\circ$. 2. The hydrodynamic characteristics depending upon slot size shows the greatest at 0.02C of the slot size. 3. Numerical results well visualized the streamlines, pressure fields, and speed vectors of a simple cambered and slot cambered otter board with slot size 0.02C. The slot cambered one with slot size 0.02C was shown that pressure field was distributed moderately on front and back side of otter board. And, the delay and decrease of separation were favorably achieved by flow through slot. 4. Computed result on the pattern of hydrodynamic field and the values of $C_L$ and $C_D$ by the commercial CFD code, FLUENT, show almost the same as those of the experimental result.

• 한국생산제조학회지
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• 제19권6호
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• pp.883-888
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• 2010

This study have goal with conceptual design for Offshore Structures of high pressure control valve for localization. Ball valve for development accomplished with flow analysis based on provision of ANSI B16.34, ANSI B16.10, ANSI B16.25 In order to localize the Offshore Structures high pressure control valve. Numerical simulation using CFD (Computational Fluid Dynamic) in order to predict a mass flow rate and a flow coefficient form flow dynamic point of view. The working fluid assumed the glycerin (C3H8O3). The valve inlet and outlet setup a pressure boundary condition. The outlet pressure was fixed by atmospheric pressure and calculated until increasing 1bar to 10bar. CFD analysis used STAR-CCM+ which is commercial code and Governing equations were calculated by moving mesh which is rotated 90 degrees when ball valve operated opening and closing in 1 degree interval. The result shows change of mass flow rate according to opening and closing angle of valve, Flow decrease observed open valve that equal percentage flow paten which is general inclination of ball valve. Relation with flow and flow coefficient can not be proportional according to inlet pressure when compare with mass flow rate. Because flow coefficient have influence in flow and pressure difference. Namely, flow can be change even if it has same Cv value. The structural analysis used ANSYS which is a commercial code. Stress analysis result of internal pressure in valve showed lower than yield strength. This is expect to need more detail design and verification for stem and seat structure.

• Nuclear Engineering and Technology
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• 제46권5호
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• pp.633-640
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• 2014

In this research, the surface roughness affecting the pressure drop in a pipe used as the steam generator of a PWR was studied. Based on the CFD (Computational Fluid Dynamics) technique using a commercial code named ANSYS-FLUENT, a straight pipe was modeled to obtain the Darcy frictional coefficient, changed with a range of various surface roughness ratios as well as Reynolds numbers. The result is validated by the comparison with a Moody chart to set the appropriate size of grids at the wall for the correct consideration of surface roughness. The pressure drop in a full-scale U-shaped pipe is measured with the same code, correlated with the surface roughness ratio. In the next stage, we studied a reduced scale model of a U-shaped heat pipe with experiment and analysis of the investigation into fluid-structure interaction (FSI). The material of the pipe was cut from the real heat pipe of a material named Inconel 690 alloy, now used in steam generators. The accelerations at the fixed stations on the outer surface of the pipe model are measured in the series of time history, and Fourier transformed to the frequency domain. The natural frequency of three leading modes were traced from the FFT data, and compared with the result of a numerical analysis for unsteady, incompressible flow. The corresponding mode shapes and maximum displacement are obtained numerically from the FSI simulation with the coupling of the commercial codes, ANSYS-FLUENT and TRANSIENT_STRUCTURAL. The primary frequencies for the model system consist of three parts: structural vibration, BPF(blade pass frequency) of pump, and fluid-structure interaction.

• 대한조선학회논문집
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• 제44권6호
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• pp.551-563
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• 2007

Numerical analysis for flow characteristics of a twin skeg container ship was carried out according to skeg vertical angles($0^{\circ}$, $10^{\circ}$, $20^{\circ}$) and skeg distances(16m, 20m, 24m) by using a commercial CFD code, FLUENT. Computed: pressure distributions, wake distributions and resistance coefficients have been compared with experimental and WAVIS results carried out by MOERI. Flow characteristics from numerical analysis such as nominal wake fractions, wake distribution and directions of the transverse vectors give good agreement with WAVIS results, even though there are quantitative discrepancy comparing with experimental measurements at the propeller plane. It is found that the better resistance performance can be obtained with the increase of the skeg vertical angle and the decrease of the skeg distance, which are mainly caused by viscous pressure resistance due to the skeg form and pressure recovery around the skeg. In addition, a vertical angle of the skeg gives more effect to the resistance coefficient comparing with the skeg distance. On the basis of results of the present study, it shows that numerical analysis using the commercial code, FLUENT, is useful and efficient tool for the evaluation of the complex stern hull form with twin-skegs.

• 한국입자에어로졸학회지
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• 제9권2호
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• pp.79-87
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• 2013

In this study, the characteristics of turbulent flow and collection efficiency for an one-stage electrostatic precipitator(ESP) with slit type collecting electrode for urban railway underground tunnels were obtained using computational fluid dynamics(CFD) commercial code FLUENT 6.3 and lab-scale experiments. The electrostatic precipitator was operated under high gas velocity(3~12m/s). Five different designs of collecting electrode, flat plate-type and a slit-type of 3mm, 5mm, 7mm and 10mm slit width and four various gas velocity(3, 6, 9, and 12m/s) were used and applied. A standard k-${\varepsilon}$ model in CFD commercial code FLUENT 6.3 was used for flow simulation. The flow simulation results showed that the turbulent intensity of flat plate-type was higher than slit-type under all gas velocity conditions and also the turbulent intensity of flat plate-type was increased continuously, but in case of slit-type was maintained at constant range. And, the turbulent intensity was decreased according to increasing of slit width. The experimental results showed that the collection efficiency of slit-type was higher than flat plate-type under all gas velocity conditions. And, over 6m/s gas velocity condition, the collection efficiency of 5mm and 7mm was highest, when compared to 3mm and 10mm.

• 해양환경안전학회지
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• 제20권5호
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• pp.552-557
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• 2014

본 연구의 목적은 1인승 보트를 설계 제작하여 시운전 및 전산유체역학(CFD)를 이용하여 속도성능을 분석하는 것이다. 선형설계를 포함한 보트의 전반적인 설계과정을 설명하였고, 설계를 바탕으로 제작된 보트에 대하여 잠잠한 해상에서 시운전을 수행했다. 시운전을 통해 보트의 설계속도에서 제동마력은 1680 W가 계측하였다. 유동해석은 상용 CFD 코드인 STAR-CCM+를 이용하여 자유수면과 동적트림을 고려하여 수행되었다. 유동해석 결과 잉여저항 성분이 마찰저항 성분에 비해 크게 나타나는 것을 확인할 수 있었다. 시운전과 CFD 결과를 바탕으로 보트의 전체효율계수를 추정하였다. 전체효율계수는 전달효율과 준 추진효율로 나누었다. 준 추진효율은 동일 프로펠러를 사용하는 솔라보트의 속도성능 추정 시 사용될 수 있다. 연구결과은 향후 개발될 보트의 선형설계, 성능분석 및 개발에 정보를 제공할 수 있다.

• 해양환경안전학회지
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• 제25권5호
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• pp.627-633
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• 2019

본 논문의 주 관심사항은 전산유체역학과 기존 모형시험 데이터를 활용하여 주어진 선박의 저항 및 추진성능을 추정하고 그 결과를 이용하여 에너지효율설계지표(Energy Efficiency Design Index, EEDI)를 평가하는 방법을 제시하는 것이다. 대상선박의 모형선 크기에서의 전 저항을 계산하기 위해 점성 유동 해석을 수행하였다. 유동계산은 STAR-CCM+를 사용하였으며 자유표면, 트림과 싱키지를 고려하였다. 점성 유동 해석 결과를 바탕으로 대상선박의 유효동력을 산정하였다. 준 추진효율 계수는 기 보유한 모형시험 데이터베이스를 이용한 추정식 및 유사선박의 시험자료를 활용하여 산정하였다. 최종적으로 EEDI 산정식에 대하여 유체동역학적 결과, 선박의 정보, 사용하는 연료에 대한 $CO_2$의 환산계수, 연료소모량 등을 바탕으로 일반화된 계산 프로그램을 작성하였다.

• 신재생에너지
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• 제2권2호
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• pp.28-36
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• 2006

Numerical analysis of wind turbine scale effect was performed by using commercial CFD code, Fluent. For the numerical analysis of wind turbine, the three dimensional Navier-Stokes solver with various turbulence models was tested. As a turbulence mode, the realizable k-e turbulence model was selected for the simulation of wind turbines. To validate the present method, performance of NREL (National Renewable Energy Laboratory) Phase VI wind turbine model was analyzed and compared with its wind tunnel test and blind test data. Using the present method, numerical simulations for various size of wind tunnel models were carried out and characteristics were analyzed in detail. For wind tunnel test model, the size of nacelle may not be scaled down precisely because of available motor. The effect of nacelle size was also computed and analyzed though CFD simulation. The present results showed the good correlations in pre-stall region but much to be improved in post-stall region. In 2006 and 2007, the performance and the scale effect of standard wind turbine model will be tested in KARI(Korea Aerospace Research Institute) LSWT(Low Speed Wind Tunnel) and the present results will be validated with the wind tunnel data.

• 한국자동차공학회논문집
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• 제21권3호
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• pp.30-42
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• 2013

This study investigates the effects of OSRVM mounting location and its configurations such as stalk height and housing height on the aerodynamic performance of the passenger car. In order to validate the flow solver, FLUENT which is very well known commercial code, the flow field around an Ahmed Body was analyzed numerically and compared with the experimental data. The predicted aerodynamic performance and flow patterns around a car show good agreements with the experimental data. Mounting location and stalk height should be designed while OSRVM is mounted on the car to evaluate the aerodynamic performance precisely. Housing height, however, may be designed independent of the car because the aerodynamic interference between housing height and car configuration is negligible.

• International Journal of Aeronautical and Space Sciences
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• 제1권1호
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• pp.13-20
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• 2000

The applications of CFD in the design process of a transonic civil transport at Korea Aerospace Research Institute (KARI) are outlined. Three Navier-Stokes solvers, developed at KARI with different grid approaches, are used to predict the aerodynamic coefficients and solve the flowfield of various configurations. Multi-block, Chimera, and unstructured grids are the approaches implemented. The accuracy of the codes is verified for the transonic flow about RAE wing/fuselage configuration. The multi-block code is used to provide the detailed data on the flowfield around a wall interference model with different test section sizes which will be used in establishing the wall interference correction method. The subsonic and transonic flowfields about K100-04A, one of the configurations of a 100-seater transport developed by KARI and Korea Commercial Aircraft Development Consortium (KCDC), are computed to predict the aerodynamic coefficients. The results for the subsonic flow are compared with those of wind tunnel test, and the agreement is found to be excellent. The interference effect of nacelle installation on the wing of K100-04A is also investigated using the unstructured grid method, and about 10% reduction in wing lift is observed. The accuracy of the three developed codes is verified, and they are used as an efficient tool in the design process of a transonic transport.