• Title/Summary/Keyword: 축대칭모델

Search Result 150, Processing Time 0.038 seconds

Three-dimensional computations of thermal plasmas and shielding gas flow of Argon in air environment

  • Lee, Won-Ho;Seo, Hyeon-Seok;Lee, Jong-Cheol
    • Proceedings of the Korean Vacuum Society Conference
    • /
    • 2015.08a
    • /
    • pp.139.1-139.1
    • /
    • 2015
  • 열플라즈마 토치 및 자유연소아크 시스템 개발이 증가함에 따라 실험을 통해 얻기 어려운 물리적 특성들을 파악하기 위해 전산유체역학을 이용한 해석방법이 널리 이용되어 왔다. 대부분의 경우에 해석의 용이성을 위하여 2차원 축대칭으로 가정하여 계산을 수행하지만, 2차원 해석만으로는 실제 물리적인 현상을 정확하게 반영하기 힘들다. 따라서 보다 실질적인 결과를 얻기 위해서는 기존의 2차원 해석방법을 3차원 해석방법으로 변환할 필요성이 있다. 본 논문에서는 3차원 열플라즈마 해석을 위한 첫 단계로써 상용 CFD 프로그램인 ANSYS CFX를 사용하여 동일한 해석모델에 관하여 2차원 해석과 3차원 해석을 수행하였다. 해석방법 및 결과의 타당성을 평가하기 위하여 Schnick-Fuessel 모델 (SF 모델)과 Haddad-Farmer 모델 (HF 모델)을 선정하여 각각의 모델에 대한 해석결과를 문헌에서 발췌한 실험결과 등과 비교하였다. 이러한 결과 비교를 통해서 본 연구에서 적용한 열플라즈마 해석에 관한 수치해석 방법이 충분히 3차원 해석으로 확장 가능함을 확인할 수 있었다.

  • PDF

A CFD Study of the Supersonic Ejector-Pump Flows (초음속 이젝터 펌프 유동에 관한 수치해석)

  • 이영기;김희동;서태원
    • Journal of the Korean Society of Propulsion Engineers
    • /
    • v.3 no.4
    • /
    • pp.58-66
    • /
    • 1999
  • The flow characteristics of supersonic ejectors is often subject to compressibility, unsteadiness and shock wave systems. The numerical works carried out thus far have been of one-dimensional analyses or some Computational Fluid Dynamics(CFD) which has been applied to only a very simplified configuration. For the design of effective ejector-pump systems the effects of secondary mass flow on the supersonic ejector flow should be fully understood. In the present work the supersonic ejector-pump flows with a secondary mass flow were simulated using CFD. A fully implicit finite volume scheme was applied to axisymmetric compressible Navier-Stokes equations. The standard two-equation turbulence model was employed to predict turbulent stresses. The results obtained showed that the flow characteristics of constant area mixing tube types were nearly independent of the secondary flow rate, but the flow fields of ejector system with the second-throat were strongly dependent on the secondary flow rate due to the effect of the back pressure near the primary nozzle exit.

  • PDF

A Study on Convergence Contact Behavior of Friction Heat and Pad on Disk Brake (디스크 브레이크에서 마찰열과 패드에 작용하는 융합 접촉거동에 관한 연구)

  • Han, Seung-Chul;Lee, Bong-Gu
    • Journal of the Korea Convergence Society
    • /
    • v.9 no.1
    • /
    • pp.283-289
    • /
    • 2018
  • In automotive disc brake systems, frictional heat is not uniformly dispersed for reasons such as heat flux and thermal deformation. The thermoelastic deformation due to the frictional heat affects the contact pressure distribution and the contact load may be concentrated on the contact portion on the the disc brake surface, resulting in thermoelastic instability. In this study, thermal analysis and thermal deformation analysis considering the contact between disk and pad occurred during braking through 3D axial symmetry model with reference to the experimental equation and Kao's analysis method of contact pressure of disk and pad. ANSYS is used to analyze the thermal and elastic instability problems occurring at the contact surface between the disk and the pad, considering both the thermal and mechanical loads. A 3D axisymmetric model with direct contact between the disk and the pad was constructed to more accurately observe the thermal behavior of the disk by observing the frictional surface temperature, thermal deformation and contact thermal stress of the disk.

Evaluation on Applicability of Finite Element Analysis in Model Test of Pile Pullout (말뚝 인발모형실험에 대한 유한요소해석의 적용성 평가)

  • You, Seung-Kyong;Shin, Heesoo;Lee, Kwang-Wu;Park, Jeong-Jun;Choi, Choong-Lak;Hong, Gigwon
    • Journal of the Korean Geosynthetics Society
    • /
    • v.18 no.2
    • /
    • pp.11-21
    • /
    • 2019
  • This paper describes the applicability of FEA(Finite Element Analysis) to the simulation of pile pullout behavior under various soil conditions (relative density and fines content), in order to evaluate reasonably the pullout resistance of pile. That is, the results of previous research (You et al., 2018) were analyzed by FEA under the same conditions. The FEA results showed that axisymmetric analysis using virtual ground was able to evaluate the skin friction of the pile. Also, axisymmetric analysis, which can apply the shear resistance characteristics of the pile-soil interface in various soil conditions, could be used as an analytical method that can simulate a reasonable pile pullout behavior. Therefore, the analytical model proposed in this study was able to simulate appropriately the pullout behavior based on the stress-strain relationship of the pile-soil interface.

Numerical Simulation for Deposition Rate Distribution of AI Film by MOCVD Process (MOCVD법에 의한 AI 박막의 증착속도 분포에 대한 수치모사)

  • Jeong, Won-Yeong;Kim, Do-Hyeon
    • Korean Journal of Materials Research
    • /
    • v.6 no.1
    • /
    • pp.99-105
    • /
    • 1996
  • 본 연구에서는 TIMA를 전구체로 하는 수직형 MOCVD 반응기를 대상으로 수학적 모델을 세우고 컴퓨터에 의한 수치모사를 수행하여 반응기 설계 변수 및 공정조건이 AI의 증착속도와 증착두께 분포에 미치는 영향을 알아보았다. 수학적 모델은 수직형 반응기를 축대칭으로 보아 2차원으로 수립하였으며 반응기내의 운동량전달, 열전달, 물질전달을 포함한다. 이 수학적 모델의 지배 방정식들에 대하여 Galerkin 유한요소법을 적용하여 수치적으로 반응기 내의 유체 흐름 구조, 온도분포와 반응물의 농도 분포를 구하였다. 수치모사 결과 AI의 증착속도는 반응기 압력이 0.47torr, 기판온도가 25$0^{\circ}C$, 유량이 7.5sccm일 경우, 190-230$\AA$/min로 나타났다.

  • PDF

The Numerical Analysis on In-cylinder Flow Fields of an Axisymmetric Engine Using $K-{\varepsilon}-{\tau}$ Turbulence Model ($K-{\varepsilon}-{\tau}$ 난류모델을 이용한 축대칭 엔진 실린더내 유동장의 수치해석)

  • 최재성
    • Journal of Advanced Marine Engineering and Technology
    • /
    • v.23 no.5
    • /
    • pp.711-718
    • /
    • 1999
  • Current turbulence models including modified $K-{\varepsilon}-{\tau}$ turbulence model do not predict compression effect on turbulence accurately in an internal combustion engine. The $K-{\varepsilon}-{\tau}$ turbulence model was suggested to improve the predictability of compression effect by We et al. In this paper a numeri-cal study was performed to clarify the applicability of the $K-{\varepsilon}-{\tau}$ turbulenc model to the calculation of the in-cylinder flow of an axisymmetric engine. THe results using $K-{\varepsilon}-{\tau}$ turbulence model are compared to those from the modified $K-{\varepsilon}-{\tau}$ turbulence model and experimental data. The mean veloc-ity and rms velocity profiles using $K-{\varepsilon}-{\tau}$ turbulence model showed a better agreement with an experimental data than those of modifid $K-{\varepsilon}-e$ turbulence model.

  • PDF

A Numerical Study of Diffusion Flames in Supersonic Flow (초음속 유동장 내의 확산 화염에 관한 수치 연구)

  • 김지호;윤영빈;정인석
    • Proceedings of the Korean Society of Propulsion Engineers Conference
    • /
    • 1997.11a
    • /
    • pp.17-17
    • /
    • 1997
  • 극초음속 여객기와 군사용 항공기에 대한 수요가 증가함에 따라서 새로운 개념의 다양한 추진기관이 연구가 진행되고 개발되어 왔다. 초음속 항공기의 속도 영역은 마하 10-20 정도가 되는데 이 속도 한계를 극복하기 위하여 초음속 연소 램제트 엔진(SCRamjet; Supersonic Combustion Ramjet)이 제안되었다. 스크램 제트를 개발하기 위해서는 연료와 산화제의 혼합 효율 문제, 화염의 안정화 문제, 벽면의 냉각에 관한 문제 등 몇 가지 기본적인 문제들을 해결해야 한다. Univ of Michigan에서 실험한 연소기를 모델로 본 연구에서는 연료와 공기의 혼합에 관한 수치 연구를 수행하였다. 다원 혼합기체에 관한 축대칭 Navier-Stokes 방정식을 지배 방정식을 이용하였고 비평형 화학반응식을 고려하였다. 공간 차분에는 유한 체적법을 이용하였다. 대류 플럭스 항은 Roe의 Upwind FDS 기법을 사용하여 차분하였고 점성항에는 중심 차분법을 이용하였다. 시간 적분법으로는 근사 자코비안과 LU분할 기법을 이용한 완전 내재적 방법이 쓰였다. 난류 모델로는 Mentor에 의해 제안된 2 방정식 k-$\varepsilon$/k-$\omega$ 혼합모델을 사용하였다. 유동장이 실험에서의 찍은 사진과 유사한 모습의 충격파 간섭을 수치 모사하였고 수소가 확산되는 모습과 함께 노즐 lip 주위의 재순환 영역에 대해서 살펴볼 수 있었다.

  • PDF

Analytic Solution to Mild Slope Equation for Transformation of Waves Propagating over an Axi-symmetric Pit (축대칭 함몰지형 위를 진행하는 파의 변형에 관한 완경사 방정식의 해석 해)

  • Jung, Tae-Hwa;Suh, Kyung-Duck
    • Journal of Korean Society of Coastal and Ocean Engineers
    • /
    • v.18 no.4
    • /
    • pp.308-320
    • /
    • 2006
  • An analytic solution to the mild-slope equation is derived for waves propagating over an axi-symmetric pit. The water depth inside the pit varies in proportion to a power of radial distance from the pit center. The governing equation is transformed into ordinary differential equations by using separation of variables, and the coefficients of the equations are transformed into explicit forms by using Hunt's (1979) approximate solution. Finally, by using the Frobenius series, the analytic solution is derived. Due to the feature of Hunt's equation, the present analytic solution is accurate in shallow and deep waters, while it is less accurate in intermediate depth water. The validity of the analytic solution is demonstrated by comparison with numerical solutions. The analytic solution is also used to examine the effects of pit geometry and relative depth on wave transformation.

A Study on Subcritical Instability of Axisymmetric Supersonic inlet (축대칭 초음속 흡입구의 아임계 불안정성 연구)

  • Shin, Phil-Kwon;Park, Jong-Ho
    • Journal of the Korean Society for Aeronautical & Space Sciences
    • /
    • v.32 no.8
    • /
    • pp.29-36
    • /
    • 2004
  • Supersonic inlet buzz can be defined as unstable subcritical operation associated with fluctuating internal pressures and a shock pattern oscillating about the inlet entrance. The flow pulsations could result in flameout in the combustor or even structural damage to the engine. An experimental study was conducted to investigate the phenomenon of supersonic inlet buzz on axisymmetric, external-compression inlet. An inlet model with a cowl lip diameter of 30mm was tested at a free stream Mach number of 2.0. Subcritical instability was investigated by considering the frequency of pressure pulsation and shock wave structure at the inlet entrance. The results obtained show that total pressure recovery ratios were varied from 0.42 to 0.78, and capture area ratio from 0.34 to 0.98. The frequency of the subcritical flow increased with decrease in capture area ratios. Frequency was measured at $224{\sim}240Hz$.

EFFECTS OF THE RING CURRENT ON ULF WAVES IN THE MAGNETOSPHERE (지구자기구의 극초저주파수 파에 대한 RING CURRENT의 효과)

  • 김관혁;이동훈
    • Journal of Astronomy and Space Sciences
    • /
    • v.11 no.1
    • /
    • pp.93-106
    • /
    • 1994
  • A three-dimensional box model has been developed to study the MHD wave coupling in the magnetosphere. In this model, the effects of the ring current are included by assuming the pressure gradients in the MHD equations. It is found that the axisymmetric ring current may play an important role in producing spectral noises in compressional waves, while field line resonances have no such disturbances. These results may explain the current observational characteristics that compressional cavity modes hardly appear in the satellite experiment, while field line resonances often occur. Our numerical resluts also suggest that any discrete spectral peaks such as the global cavity modes can hardly occur where the pressure distribution of the ring current becomes important. The continuous band of transverse waves is found to be unperturbed until the ring current becomes significantly asymmetric with respect to the dipole axis. In addition, our results in the absence of the pressure gradient are found to be consistent with the previous results from the box-like and dipole models.

  • PDF