• 제목/요약/키워드: Numerical data

검색결과 7,290건 처리시간 0.035초

표류(漂流)를 고려한 선체운동(船體運動) (The Effect of The Drift Velocity on The Ship Motion)

  • 황종흘;김용직
    • 대한조선학회지
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    • 제18권3호
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    • pp.29-38
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    • 1981
  • In general the drift result in ship heeling, thus it seems to be necessary to analyze the ship motion by considering both the drifting and heeling phenomena. In this paper, a drift velocity and a heeling angle are given as prior conditions, and then within the linear potential theory the hydrodynamic coefficients and wave exciting forces and moments are derived for a ship advancing and drifting with constant speeds. And numerical calculations are preformed for a cylindrical body of shiplike cross section at zerp forward velocity. The 2-D hydrodynamic forces and moments of a heeled cylinder are calculated by using the Frank Close-Fit method. These numerical results for the oscillating cylinder without drift velocity have shown better agreements with experimental data than the numerical results of Kobayashi[2]. The motion responses for a drifting cylinder are calculated ignoring the drift velocity effect in the free surface condition. The accuracy of these calculations can not be verified, because the experimental data are not available. Through these numerical calculations to so concluded that drift velocity effects on the body motion are signiffcant.

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전산유체역학을 이용한 풍력터빈 축소효과 수치해석 (Numerical Analysis of Wind Turbine Scale Effect by Using Computational Fluid Dynamics)

  • 박영민;장병희
    • 한국신재생에너지학회:학술대회논문집
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    • 한국신재생에너지학회 2006년도 춘계학술대회
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    • pp.269-272
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    • 2006
  • Numerical analysis of wind turbine scale effect was performed by using computational fluid dynamics. For the numerical analysis of wind turbine. Three dimensional Navier-Stokes solver with various turbulence models was tested and 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 experiment and blind test data. Using the present method, numerical simulations for various size of wind tunnel model were carried out and characteristics were observed in detail. The power loss due to the interference between wind turbine and nacelle was also computed for relatively larger nacelle installation in wind tunnel test. The present results showed good correlations with experimental data and reasonable trends of scale effect of wind turbine.

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An innovative method for determining the diffusion coefficient of product nuclide

  • Chen, Chih-Lung;Wang, Tsing-Hai
    • Nuclear Engineering and Technology
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    • 제49권5호
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    • pp.1019-1030
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    • 2017
  • Diffusion is a crucial mechanism that regulates the migration of radioactive nuclides. In this study, an innovative numerical method was developed to simultaneously calculate the diffusion coefficient of both parent and, afterward, series daughter nuclides in a sequentially reactive through-diffusion model. Two constructed scenarios, a serial reaction (RN_1 ${\rightarrow}$ RN_2 ${\rightarrow}$ RN_3) and a parallel reaction (RN_1 ${\rightarrow}$ RN_2A + RN_2B), were proposed and calculated for verification. First, the accuracy of the proposed three-member reaction equations was validated using several default numerical experiments. Second, by applying the validated numerical experimental concentration variation data, the as-determined diffusion coefficient of the product nuclide was observed to be identical to the default data. The results demonstrate the validity of the proposed method. The significance of the proposed numerical method will be particularly powerful in determining the diffusion coefficients of systems with extremely thin specimens, long periods of diffusion time, and parent nuclides with fast decay constants.

Reliability of numerical computation of pedestrian-level wind environment around a row of tall buildings

  • Lam, K.M.;To, A.P.
    • Wind and Structures
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    • 제9권6호
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    • pp.473-492
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    • 2006
  • This paper presents numerical results of pedestrian-level wind environment around the base of a row of tall buildings by CFD. Four configurations of building arrangement are computed including a single square tall building. Computed results of pedestrian-level wind flow patterns and wind speeds are compared to previous wind tunnel measurement data to enable an assessment of CFD predictions. The CFD model uses the finite-volume method with RNG $k-{\varepsilon}$ model for turbulence closure. It is found that the numerical results can reproduce key features of pedestrian-level wind environment such as corner streams around corners of upwind building, sheltered zones behind buildings and channeled high-speed flow through a building gap. However, there are some differences between CFD results and wind tunnel data in the wind speed distribution and locations of highest wind speeds inside the corner streams. In locations of high ground-level wind speeds, CFD values match wind tunnel data within ${\pm}10%$.

미분 석유코크스연소기에서 스월강도변화가 연소과정에 미치는 영향 (The Effects of Various Swirl Flows on Pulverized Petroleum Coke Combustion)

  • 차천륜;이호연;황상순
    • 한국연소학회:학술대회논문집
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    • 한국연소학회 2014년도 제49회 KOSCO SYMPOSIUM 초록집
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    • pp.297-299
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    • 2014
  • Petroleum coke has high heating value and low price. Due to the steadily increasing demand for heavy oil processing, the production volume of petroleum coke tends to be expanded. The high availability and low price of petroleum coke have been strongly considered as candidate fuel for power generation facilities. However the high carbon content, high sulfur content and nitrogen content of petroleum fuel are known to produce relatively large quantity of CO2, high NOx and SO2 emission. In this work, a series of numerical simulations have been carried out in order to investigate the effects of swirl flow intensity on combustion furnace, which is most important operating condition. Results show that the temperature distribution was spatially uniform at about 1600K but high temperature region are located quite differently depending on swirl number. In addition, numerical temperature data was compared with experimental temperature data and its temperature difference shows less than 10%. On the other hand, discrepancy between numerical and experimental emission data were slightly large with necessities of improved emission model.

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Finite Element Analysis for Wavelike Flow Marks in Injection Molding

  • Kang, Sung-Yong;Lee, Woo-Il
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 2003년도 The Korea-Japan Plastics Processing Joint Seminar
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    • pp.27-32
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    • 2003
  • The wavelike flow mark phenomenon is one of the surface defects that can arise during the injection stage of the injection molding process. We have performed a numerical analysis using a finite element method for the injection molding to verify the validity of 'Go-over' hypothesis. Also, we have compared the results of numerical analysis with available experimental data. Numerical analysis results of the flow marks are qualitatively in good agreement with experimental data of reference, but are quantitatively deviated from experimental data in a consistent manner. A parametric study has been performed to examine the correlative effects of various injection molding processing parameters and material properties on the flow mark size.

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배수방식에 따른 온수 방류의 3차원 수치모의 (A Three-Dimensional Numerical Model of Thermal Discharge for Different Type of Effluent)

  • 이진우;이승오;김창완;조용식
    • 한국방재학회:학술대회논문집
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    • 한국방재학회 2007년도 정기총회 및 학술발표대회
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    • pp.387-390
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    • 2007
  • The mixing characteristics of heated water discharged from different types of effluents are simulated using a commercial software, Flow-3D model. In order to verify the model, the comparison of numerical results with the experimental data are conducted for each type of effluent, the submerged and surface overfall. It is observed that the numerical results show a reasonable agreement with the experimental data. Based on this study the application to the heated water discharge problem in the field can be expected as a further study and it can be the fundamental data when determining the type of effluent in a powerplant.

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스윕을 가진 냉각탑용 축류홴의 성능 특성에 관한 수치해석적 연구 (Numerical Investigation of Performance Characteristics for Cooling Tower Axial Fans with Sweep)

  • 오건제
    • 동력기계공학회지
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    • 제13권4호
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    • pp.31-37
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    • 2009
  • The purpose of this numerical study was to investigate performance characteristics for cooling tower axial fans with sweep. Performance data for the fans with various sweep angles were obtained in terms of the setting angle at a constant flow rate. Viscous flow calculations were carried out to obtain Performance data of the total pressure rise and hydraulic efficiency. A solution of the Ffowcs Williams-Hawkings equations was used to calculate the sound pressure level at three times fan diameter away from the fan. The calculated performance data well represented performance characteristics of the cooling tower axial fan. The total pressure rise and hydraulic efficiency at the same setting angle decreased with sweep angle. Sound pressure level slightly decreased for the fan with a sweep angle of 10 degree. No significant effect of the sweep geometry was found on the sound pressure level.

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Aerodynamic Noise Prediction of Subsonic Rotors

  • Lee, Jeong-Han;Lee, Soo-Gab
    • The Journal of the Acoustical Society of Korea
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    • 제16권1E호
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    • pp.29-34
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    • 1997
  • Numerical prediction of aerodynamic noise radiated by subsonic rotors are carried out. A computer program has been developed which incorporates both the discrete frequency noise as well as the broadband noise arising from the ingestion of turbulence. Acoustic analogy is used in conjunction with Homicz's formulation of turbulence ingestion noise. Formulation 1A of Farassat is used to enhance the numerical analysis performance of Ffowcs-Williams Hawkings equation by eliminating the numericla time differentiation. Homicz's trubulence ingestion noise prediction technique is used to understand the characteristics of broadband noise radiated by isotropic trubulence in gestion. Numerical predictions are carried out for a number of rotor configurations and compared with experimental data. Monopole consideration of transonic rotor agrees well with both the experimental data and the linear theory. Noise radiation characteristics of rotor at lifting hover are investigated utilizing simple blade loading obtained by thin wing section theory. By incorporating discrete noise prediction of steady loading with broadband spectrum, much better agreement with experimental data is obtained in the low frequency region. The contributions from different noise mechanisms can also be analyzed through this method.

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An Application of a Sunshine Duration Model Based on GIS Data to Suitability of Measurement Site around the Seonleung Park

  • Kim, Eun-Ryoung;Kim, Jae-Jin
    • 대한원격탐사학회지
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    • 제31권4호
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    • pp.331-336
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    • 2015
  • In this study, a numerical model developed for sunshine duration based on GIS data was used. This model considers blocking caused by topography and buildings and it is properly applicable to evaluation of sunshine duration environment in urban areas. The model reasonably well predicted the solar altitude and azimuth angels, compared to those provided by Korea Astronomy and Space Science Institute (KASI). The developed model was applied to evaluation of sunshine duration environment around the Seonleung Park located near a building-congested area in Seoul. The model well reproduced shadow caused by buildings and/or topography in the numerical domain at 09:00 on August 1, 2015. In addition, the model was applied to finding a suitable measurement sites for pyrheliometer around the Seonleung Park. The model was also usefully applied to finding a suitable site for pyrheliometer in an urban area.