http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
보정한 Bleed 모델을 이용한 초음속 흡입구 버즈 제어
곽인근(E. Kwak),이승수(S. Lee) 한국전산유체공학회 2013 한국전산유체공학회지 Vol.18 No.4
Database of a bleed model has been corrected and numerical simulations have been performed to control buzz using the corrected bleed model. The existing bleed model, which was developed as a part of a boundary condition model for porous bleed walls, underestimates bleed flow rate because flow accelerations near the bleed regions are ignored. Also, it overpredicts the sonic flow coefficient when the bleed plenum pressure ratio is high. To correct these problems, and to enhance the performance of the bleed model, the database has been corrected using CFD simulations to compensate for the flow acceleration near the bleed region. Futhermore, the database of the bleed model is extended with the second order extrapolation. The corrected bleed model is validated with numerical simulations of a shock-boundary layer interaction problem over a solid wall with a bleed region. Using the corrected bleed model, numerical simulations of supersonic inlet buzz are performed to find the deterrent effects of bleed on buzz. The results reveal that bleed is effective to prevent buzz and to enhance the inlet performance.
보존형 형태의 S-A 난류 모델 방정식을 이용한 이차원 유동 해석
곽인근(E. Kwak),백지영(J.Y. Baek),이승수(S. Lee) 한국전산유체공학회 2012 한국전산유체공학회 학술대회논문집 Vol.2012 No.5
Numerical simulations of two dimensional flows are performed with a conservative form of S-A turbulence model and the simulation results are compared to those of the standard form and the compressible form. The conservative form is derived, from the standard form, which is in non-conservative form, using the continuity equation. The model constant of the conservative form is corrected to compensate for the differences between the conservative and the non-conservative discretizations. For verification of the conservative form of the equation, flows over a flat plate at various flow conditions are computed and the results are compared to those of the other forms as well as other computational results and theories. For subsonic flows, little difference is observed between the results of three forms. For supersonic and hypersonic flows, however, skin frictions of the compressible form and the conservative form are slightly larger than that of the standard form. Furthermore, numerical simulations of a transonic flow around an airfoil are performed with three forms and usefulness of the conservative form is confirmed by obtaining reasonable results.
축대칭 초음속 흡입구 주위의 저주파수 및 고주파수 버즈(Buzz) 에 대한 수치모사
곽인근(E. Kwak),이승수(S. Lee) 한국전산유체공학회 2012 한국전산유체공학회 학술대회논문집 Vol.2012 No.11
In this paper, numerical simulations of both low- and high-frequency buzz phenomena at the throttle ratio (T.R.) found in Nagashimas experiment are performed. The dominant frequencies of low- and high- frequency buzz in the experiment are about 109 Hz with T.R.=0.97 and 376 Hz with T.R,=0.55, respectively. An axisymmetric solver with the S-A turbulence model and the SST turbulence model is used in the simulations and DFT on pressure histories is conducted for the buzz frequency analysis. In the present simulations, the free-stream Mach number and the Reynolds number bases on the inlet diameter are 2 and 10<SUP>7</SUP>, respectively. Both low- and high-frequency buzz phenomena are simulated successfully without changes in the grid topology. The dominant frequency of the simulation is about 125 Hz with T.R.=0.97, while it is 399 Hz with T.R.=0.55.
다공성 벽면(porous-wall)과 거칠기가 있는 벽면(rough-wall)에 관한 경계조건을 이용한 초음속 흐름의 수치모사
곽인근(E.K. Kwak),유일용(I.Y. Yoo),이승수(S. Lee) 한국전산유체공학회 2009 한국전산유체공학회 학술대회논문집 Vol.2009 No.4
The existing code which solves two-dimensional RANS(Reynolds Averaged Navier-Stokes) equations and 2-equation turbulence model equations was modified to enable numerical simulation of various supersonic flows. For this, various boundary conditions have been implemented to the code. Bleed boundary condition was incorporated into the code for calculating wall mean flow quantities. Furthermore, the boundary conditions for the turbulence quantities along rough surfaces as well as porous walls were applied to the code. The code was verified and validated by comparing the computational results against the experimental data for the supersonic flows over bleed region on a flat plate. Using the newly modified code, numerical simulations were performed and compared with other computational results as well as the experimental data for the supersonic flows over an oblique shock with a bleed region.
곽인근(E. Kwak),공효준(H. Kong),이승수(S. Lee) 한국전산유체공학회 2011 한국전산유체공학회 학술대회논문집 Vol.2011 No.11
Database of a bleed model, which was developed as a part of a boundary condition model for porous bleed wall, has been corrected using CFD simulations to enhance the performance of the bleed model. The existing bleed model underestimates bleed flow rate because flow acceleration near bleed regions is ignored. Also, it overpredicts sonic flow coefficient when the bleed plenum pressure ratio is high. To correct these problems, and to enhance the performance of the bleed model, the database has been corrected using CFD simulations to compensate the flow acceleration near the bleed region. Furthermore, the database of the bleed model is extended with second order extrapolation. Numerical simulations of a shock-boundary layer interaction problem over a solid wall with a bleed region reveal that the modified database gives more accurate results than the existing database.
축대칭 초음속 흡입구 주위의 저주파수 및 고주파수 버즈(Buzz)에 대한 수치모사
곽인근(E. Kwak),이남훈(N. Lee),공효준(H. Gong),이승수(S. Lee) 한국전산유체공학회 2013 한국전산유체공학회지 Vol.18 No.2
In this paper, numerical simulations of both low- and high-frequency buzz phenomena at the throttle ratios (T.R.) in Nagashimas experiment are performed. The dominant frequencies of the low-and high-frequency buzz in the experiment are about 109 Hz with T.R.=0.97 and 376 Hz with T.R.=0.55, respectively. An axisymmetric solver with the S-A turbulence model is used for the simulations, and DFT(Discrete Fourier Transform) on pressure histories is conducted for the buzz frequency analysis. In the present simulations, the free-stream Mach number and the Reynolds number based on the inlet diameter are 2 and 107, respectively. Both the low- and high-frequency buzz phenomena are accomplished without the changes in the grid topology. The dominant frequency of the simulation is about 125 Hz with T.R.=0.97, while it is 399 Hz with T.R.=0.55.
다공성 벽면(porous-wall)과 거칠기가 있는 벽면(rough-wall)에 관한 경계조건을 이용한 초음속 흐름의 수치모사
곽인근(E.K. Kwak),유일용(I.Y. Yoo),이동훈(D.H. Lee),이승수(S. Lee) 한국전산유체공학회 2009 한국전산유체공학회지 Vol.14 No.4
The existing code which solves two-dimensional RANS(Reynolds Averaged Navier-Stokes) equations and 2-equation turbulence model equations was modified to enable numerical simulation of various supersonic flows. For this, various boundary conditions have been implemented to the code. Bleed boundary condition was incorporated into the code for calculating wall mean flow quantities. Furthermore, boundary conditions for the turbulence quantities along rough surfaces as well as porous walls were applied to the code. The code was verified and validated by comparing the computational results against the experimental data for the supersonic flows over bleed region on a flat plate. Furthermore, numerical simulations for supersonic shock boundary layer interaction with a bleed region were performed and their results were compared with the existing computational results.
보정한 Bleed 모델을 이용한 초음속 흡입구 버즈 제어
곽인근(E. Kwak),이승수(S. Lee) 한국전산유체공학회 2013 한국전산유체공학회지 Vol.18 No.4
Database of a bleed model has been corrected and numerical simulations have been performed to control buzz using the corrected bleed model. The existing bleed model, which was developed as a part of a boundary condition model for porous bleed walls, underestimates bleed flow rate because flow accelerations near the bleed regions are ignored. Also, it overpredicts the sonic flow coefficient when the bleed plenum pressure ratio is high. To correct these problems, and to enhance the performance of the bleed model, the database has been corrected using CFD simulations to compensate for the flow acceleration near the bleed region. Futhermore, the database of the bleed model is extended with the second order extrapolation. The corrected bleed model is validated with numerical simulations of a shock-boundary layer interaction problem over a solid wall with a bleed region. Using the corrected bleed model, numerical simulations of supersonic inlet buzz are performed to find the deterrent effects of bleed on buzz. The results reveal that bleed is effective to prevent buzz and to enhance the inlet performance.
가상 압축성 기법을 이용한 이차원 비압축성 유동의 수치모사
이형로(H.R. Lee),유일용(I.Y. Yoo),곽인근(E.K. Kwak),이승수(S. Lee) 한국전산유체공학회 2010 한국전산유체공학회 학술대회논문집 Vol.2010 No.5
In this paper, a new computational code was developed using Chorins artificial compressibility method to solve the two-dimensional incompressible Navier-Stokes equations. In spatial derivatives, Roes flux difference splitting was used for the inviscid flux, while central differencing was used for the viscous flux. Furthermore, AF-ADI with dual time stepping method was implemented for accurate unsteady computations. Two-equation turbulence models, Menters k-ω SST model and Coakleys q-ω model, have been adopted to solve high-Reynolds number flows. A number of numerical simulations were carried out for steady laminar and turbulent flow problems as well as unsteady flow problem. The code was verified and validated by comparing the results with other computational results and experimental results. The results of numerical simulations showed that the present developed code with the artificial compressibility method can be applied to solve steady and unsteady incompressible flows.