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변분다중스케일법을 이용한 $Re_{\tau}=180$ 채널 난류 유동의 대와류모사
장경식,이보현,윤범상,이주성,노명일,Chang, K.,Lee, B.H.,Yoon, B.S.,Lee, J.S.,Roh, M.I. 한국전산유체공학회 2010 한국전산유체공학회지 Vol.15 No.2
In the present work, LES with new variational multiscale method is conducted on the fully developed channel flow with Reynolds number, 180 based on the friction velocity and the channel half width. Incompressible Navier-Stokes equations are integrated using finite element method with the basis function of NURBS. To solve space-time equations, Newton's method with two stage predictor multicorrector algorithm is employed. The code is parallelized using MPI. The computational domain is a rectangular box of size $2{\pi}{\times}2{\times}4/3{\pi}$ in the streamwise, wall normal and spanwise direction. Mean velocity profiles and velocity fluctuations are compared with the data of DNS. The results agree well with those of DNS and other traditional LES.
Hybrid RANS/LES 방법을 이용한 아음속 공동 유동의 수치적 모사
장경식(K. S. Chang),박승오(S. O. Park),최석기(S. K. Choi) 한국전산유체공학회 2004 한국전산유체공학회지 Vol.9 No.2
A numerical simulation of an incompressible cavity flow is conducted using the hybrid turbulence model. The model adopted is a modified type of DES using k-ε two-equation model. Cavity geometry and flow condition are based on Cattafesta's experiment. Computational results are compared with the results of Cattafesta's experiment. The simulation successfully predicts the oscillatory features and the Strouhal number of the oscillation compares very favorably with that of the dominant mode of experimental data. Vorticity contours obtained from the simulation data are consistent with the smoke visualization of the Cattafesta's experiment. The coherent structures of cavity flow are also investigated using Q criterion.
BWB UCAV 형상 주변의 유동해석에 대한 천이모델의 예측능력 연구
조영희(Y.H. Jo),장경식(K.S. Chang),신동진(D.J. Sheen) 한국전산유체공학회 2014 한국전산유체공학회 학술대회논문집 Vol.2014 No.11
A computational simulation for a nonslender BWB UCAV configuration with rounded leading edge and span of 1.0m was performed to analyze its aerodynamic characteristics at low A.o.A.s. Reynolds number based on the mean chord length is 1.25 million. γ-Re<SUB>θ</SUB> transition model and k-ω SST model was used to assess effect of transition for flow behavior. Also γ transition model that accounts for crossflow instability effects was employed to investigate crossflow instability effects in three-dimensional boundary layer on the UCAV aerodynamic surfaces. After assessing aerodynamic coefficients and lift to drag, it was found that crossflow effects plays an important roles at given flow condition.
변분다중스케일법을 이용한 Re<SUB>T</SUB>=180 채널 난류 유동의 대와류모사
장경식(K. Chang),이보현(B.H. Lee),윤범상(B.S. Yoon),이주성(J.S. Lee),노명일(M.I. Roh) 한국전산유체공학회 2010 한국전산유체공학회지 Vol.15 No.2
In the present work, LES with new variational multiscale method is conducted on the fully developed channel flow with Reynolds number, 180 based on the friction velocity and the channel half width. Incompressible Navier-Stokes equations are integrated using finite element method with the basis function of NURBS. To solve space-time equations, Newton's method with two stage predictor multicorrector algorithm is employed. The code is parallelized using MPI. The computational domain is a rectangular box of size 2π×2×4/3π in the streamwise, wall normal and spanwise direction. Mean velocity profiles and velocity fluctuations are compared with the data of DNS. The results agree well with those of DNS and other traditional LES.
변분다중스케일법을 이용한 Re<SUB>τ</SUB>=180 채널 난류 유동의 대와류모사
장경식(K. Chang),이보현(B.H. Lee),윤범상(B.S. Yoon),이주성(J.S. Lee),노명일(M.I. Roh) 한국전산유체공학회 2009 한국전산유체공학회 학술대회논문집 Vol.2009 No.11
In the present work, LES with new variational multiscale method is conducted on the fully developed channel flow with Reynolds number is 180 based on the friction velocity and the channel half width. Incompressible Navier-Stokes equations are integrated using finite element method with the basis function of NURBS. To solve space-time equations, Newton's method with two stage predictor multicorretor algorithm is employed. The code is parallelized using MPI. The computational domain is a rectangular box of size 2π×2×4/3π in the stream wise, wall normal and span wise direction. Mean velocity profiles and velocity fluctuations are compared with the data of DNS. The results agree well with those of DNS and other traditional LES.
DES 방법을 이용한 비압축성 열린 공동 유동의 수치적 모사
장경식(K.S. Chang),박승오(S.O. Park),권오준(O.J. Kwon),G. Constantinescu 한국전산유체공학회 2005 한국전산유체공학회지 Vol.10 No.3
Three-dimensional incompressible flow past an open cavity in a channel is investigated using Detached Eddy Simulation(DES). The length to depth ratio of the cavity is 2 and the Reynolds number defined with the cavity depth is 3,360. The DES methods are based on the Menter's SST model. In the present work, two types of inflow conditions are used; one is RANS profile, the other is LES inflow from another Large Eddy Simulation(LES) of fully developed channel flow. The results are compared with experimental data and LES results in terms of the mean statistics, temporal physics and scalar transport phenomenon of the flow.
대와류모사 기법을 이용한 다공성 실린더 주위의 유동 해석
장경식(K.S. Chang) 한국전산유체공학회 2012 한국전산유체공학회 학술대회논문집 Vol.2012 No.5
The presence of a layer of vegetation which is relevant in river engineering or coastal engineering can modify the overall flow resistance, turbulent characteristics of flow. The patch of vegetation can be modelled and studied in a simple porous cylinder by previous researchers. Fully three dimensional Large Eddy Simulation is conducted in flow past a porous cylinder with a solid volume fraction (SVF) Of 20%. The porous cylinder of diameter D contains 89 smaller cylinders which diameter is 0.04D in a regular staggered way. Reynolds number based on porous cylinder diameter D and the bulk velocity is 10,000. The difference in the dynamics of the separated shear layer and the streamwise flow penetrating through the porous cylinder are compared with those in the non-porous cylinder. In particular, the wake billows form a larger distance from the back of the porous cylinder.