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Ahmed body 주위의 난류유동장 해석에 대한 난류모델의 평가
명현국(H.K.Myong),박희경(H.K.Park) 한국자동차공학회 1995 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1995 No.11_2
A numerical simulation has been carried out for three-dimensional turbulent flows around an Ahmed body. The full Navier-Stokes equation is solved with the SIMPLE method in general<br/> curvi I inear coordinates system.. Several k-ε turbulence mode I s wi th two convective difference<br/> schemes are evaluated for the performance such as drag coefficient, velocity and pressure fields. The results of simulation prove that the RNG k-ε model with a quadratic upwind difference scheme predicts fairely well the tendency of velocity and pressure fields and gives more reliable drag coefficient.<br/>
엇갈린 V-형 리브가 부착된 냉각유로에서의 열유동 수치해석
명현국(H.K. Myong),김광용(K.Y. Kim) 한국전산유체공학회 2008 한국전산유체공학회지 Vol.13 No.4
The present study numerically simulates the flow and heat transfer characteristics of rib-induced secondary flow in a square cooling channel with staggered V-shaped ribs, extruded on both walls. The rib pitch-to-height ratio (p/h) varies from 2.8 to 10 with the rib-height-to-hydraulic diameter ration (h/D<SUB>h</SUB>) of 0.07 and the Reynolds number of 50,000. Shear stress transport (SST) turbulence model is used as a turbulence model. Computational results show that complex secondary flow patterns are generated in the channel due to the snaking flow in the streamwise direction for all tested cases. In the range of p/h=5 to 10 the staggered V-shaped rib gives about 3 times higher heat transfer augmentation than the reference smooth pipe with high heat transfer on both front side and the area around the leading edge of the ribs, while the former cases give about 18 times higher streamwise pressure drop than the latter ones. However, for the thermal performances, based on the equal pumping power condition, the case of p/h=2.8 gives the best result among three cases, mainly due to relatively low streamwise pressure drop, although it gives relatively low heat transfer augmentation.
Ahmed Body 주위의 3차원 난류유동 해석 - 난류모델의 평가
명현국,진은주,박희경,Myong, H.K.,Jin, E.,Park, H.K. 대한기계학회 1997 大韓機械學會論文集B Vol.21 No.7
A numerical simulation has been carried out for three-dimensional turbulent flows around an Ahmed body. The Reynolds-averaged Navier-Stokes equation is solved with the SIMPLE method in general curvilinear coordinates system. Several k-.epsilon. turbulence models with two convective difference schemes are evaluated for the performance such as drag coefficient, velocity and pressure fields. The drag coefficient, the velocity and pressure fields are found to be changed considerably with the adopted k-.epsilon. turbulence models as well as the finite difference schemes. The results of simulation prove that the RNG k-.epsilon. model with the QUICK scheme predicts fairly well the tendency of velocity and pressure fields and gives more reliable drag coefficient. It is also demonstrated that the large difference between simulations and experiment in the drag coefficient is due to relatively high predicted values of pressure drag from vertical rear end base.
엇갈린 V-형 리브가 부착된 냉각유로에서의 열유동 수치해석
명현국(H.K. Myong),김광용(K.Y. Kim) 한국전산유체공학회 2008 한국전산유체공학회 학술대회논문집 Vol.2008 No.-
The present study numerically simulates the flow and heat transfer characteristics of rib-induced secondary flow in a cooling channel with staggered V-shaped ribs, extruded on both walls. The rib pitch-to-height ratio (p / h) varies from 2.8 to 10 with the rib-height-to-hydraulic diameter ration (h/Dh) of 0.07 and the Reynolds number of 50,000. Shear stress transport (SST) turbulence model is used as a turbulence model. Computational results show that complex secondary flow patterns are generated in the duct due to the snaking flow in the streamwise direction for all tested cases. In the range of p/h=5 to 10 the staggered V-shaped rib gives about 3 times higher heat transfer augmentation than the reference smooth channel with high heat transfer on both front side and the area around the leading edge of the ribs, while the former cases give about 2.5 times higher streamwise pressure drop than the latter ones. Consequently, for the thermal performances, based on the equal pumping power condition, the staggered ones give about 2 times higher values than the latter ones with more uniform heat transfer distribution.
유한차분 도식에 따른 건물 계단통에서의 3차원 부력 난류유동 수치해석
명현국,Myong, H.K. 대한설비공학회 1999 설비공학 논문집 Vol.11 No.1
This paper describes a numerical study of three-dimensional buoyant turbulent flow in a stairwell model with three convective differencing schemes, which include the upwind differencing scheme, the hybrid scheme and QUICK scheme. The Reynolds-averaged Navier-Stokes and energy equations are solved with a two-equation turbulence model. The Boussinesq approximation is used to model buoyancy terms in the governing equations. Three-dimensional predictions of the velocity and temperature fields are presented and are compared with experimental data. Three-dimensional simulations with each scheme have predicted the overall features of the flow fairly satisfactorily. A better agreement with experimental is achieved with QUICK scheme.
비정렬 셀 중심 방법에서 대류플럭스의 수치근사방법 평가
명현국(H.K. Myong) 한국전산유체공학회 2006 한국전산유체공학회지 Vol.11 No.1
The existing numerical approximations of convection flux, especially the spatial higher-order difference schemes, in unstructured cell-centered finite volume methods are examined in detail with each other and evaluated with respect to the accuracy through their application to a 2-D benchmark problem. Six higher-order schemes are examined, which include two second-order upwind schemes, two central difference schemes and two hybrid schemes. It is found that the 2nd-order upwind scheme by Mathur and Murthy(1997) and the central difference scheme by Demirdzic and Muzaferija(1995) have more accurate prediction performance than the other higher-order schemes used in unstructured cell-centered finite volume methods.
비정렬 셀 중심방법 및 경계면포착법을 사용하는 3차원 유동해석코드(PowerCFD)에 적합한 HR 해법에 관한 연구
명현국(H.K. Myong),김종은(J.E. Kim) 한국전산유체공학회 2008 한국전산유체공학회지 Vol.13 No.1
Several high resolution schemes such as OSHER, MUSCL, SMART, GAMMA, WACEB and CUBISTA are comparatively studied with respect to the accurate capturing of fluid interfaces throughout the application to two typical test cases of a translation test and a collapsing water column problem with a return wave. It is accomplished by implementing the high resolution schemes in the in-house CFD code(PowerCFD) for computing 3-D flow with an unstructured cell-centered method and an interface capturing method, which is based on the finite-volume technique and fully conservative. The calculated results show that SMART scheme gives the best performance with respect to accuracy and robustness.
명현국(H.K. Myong) 한국전산유체공학회 2011 한국전산유체공학회 학술대회논문집 Vol.2011 No.5
This paper presents a numerical study on multiphase flows induced by wall adhesion. The CSF(Continuum Surface Force) model is used for the calculation of the surface tension force and implemented in an in-house solution code(PowerCFD). The present method(code) employs an unstructured cell-centered method based on a conservative pressure-based finite-volume method with volume capturing method(CICSAM) in a volume of fluid(VOF) scheme for phase interface capturing. As an application of the present method, the effects of wall adhesion are numerically simulated with the CSF model for a shallow pool of water located at the bottom of a cylindrical tank. Two different cases are computed, one in which the water wets the wall and one in which the water does not wet the wall. It is found that the present method simulates efficiently and accurately surface tension-dominant multiphase flows induced by wall adhesion.