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다양한 $k-{\varepsilon}$ 난류모델과 Skew-Upwind 기법에 의한 단이 진 벽면분류에 대한 수치해석
서호택,부정숙,Seo, Ho-Taek,Boo, Jung-Sook 대한기계학회 2000 大韓機械學會論文集B Vol.24 No.2
Four turbulent $k-{\varepsilon}$ models (i.e., standard model, modified models with streamline curvature modification and/or preferential dissipation modification) are applied in order to analyze the turbulent flow of wall-attaching offset jet. For numerical convergence, this paper develops a method of slowly increasing the convective effect induced by skew-velocity in skew-upwind scheme (hereafter called Partial Skewupwind Scheme). Even though the method was simple, it was efficient in view of convergent speed, computer memory storage, programming, etc. The numerical results of all models show good prediction in first order calculations (i.e., reattachment length, mean velocity, pressure), while they show some deviations in ·second order (i.e., kinetic energy and its dissipation rate). Like the previous results obtained by upwind scheme, the streamline curvature modification results in better prediction, while the preferential dissipation modification does not.
박종규,서성호,부정숙,Park Jong-Kyu,Seo Seong-Ho,Boo Jung Sook 한국마린엔지니어링학회 2005 한국마린엔지니어링학회지 Vol.29 No.8
This experimental study is conducted to investigate effects of a splitter plate, which is set on the back side of a square prism in the uniform flow. The Reynolds number is $1.44{\times}10^{4}$ based on the width of the square prism. The measurement of velocity vector and pressure distribution are carried out 4 cases of length in the range of 0.5L to 2.0L with 0.5L interval and 3 cases of Position at 0L, 0.25L, 0.5L, Flow visualization is also executed by smoke-wire method to understand the mechanism of vortex formation The results show the strong vortex shedding patterns and drags are decreased effectively, when the position of splitter plate is 0L. And the drag reduction rate is in inverse proportion to the splitter plate length
류병남(Byong Nam Ryu),김경천(Kyung Chun Kim),부정숙(Jung Sook Boo) 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.3
The characteristics of near wakes of circular cylinders with serrated fins arc investigated experimentally using a hot-wire anemometer for various frccstrcam velocities. Near wake structures of the fin lubes arc observed using a phase average technique With increasing fin height and decreasing fin pitch, oscillation of streamwise velocity increases, while oscillation of lateral velocity decreases. The time averaged V-componcnt velocity distribution of the finned tube is contrary to that of the circular cylinder due to the different strength of entrainment flow. This strength is affected by the distance of ?/U_0 = 1.0 contour lines. ?/U_0 = 1.0 contour line approaches to the wake center line when the fin density is increased When the distance between ?/U_0 = 1.0 contour lines comes close, the shear force should be increased and the flow toward the wake center line can be more strengthened because of the shear force. Factors related to the velocity recovers in the near wake of the finned tube are attributed to the turbulent intensity, the boundary layer thickness, the position and strength of cntrainment process.<br/>
박종규(Jong-Kyu Park),서성호(Seong-Ho Seo),부정숙(Jung-Sook Boo) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
This experimental study is conducted to investigate the effect of a splitter plate, which is set on the back side of a square prism in the uniform flow, Re=1.44×10⁴. The measurement of velocity vector and pressure distribution are carried out 4 cases of length in the range of 0.5ℓ to 2.0ℓ with 0.5ℓ interval and 3 cases of position at 0ℓ, 0.25ℓ, 0.5ℓ. Flow visualization is also executed by smoke-wire method to understand the mechanism of vortex fprmation. The results show the strong vortex shedding patterns and drags are decreased effectively, when the position of splitter plate is 0ℓ. and the drag reduction rate is in inverse proportion to the splitter plate length.
류병남(Byong Nam Ryu),김경천(Kyung Chun Kim),부정숙(Jung Sook Boo) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.4
An experimental study is performed to investigate the characteristics of near wake behind a circular cylinder with serrated fins using constant temperature anemometer and flow visualization. Previous report(Boo et al., 2001) shows that there are three different modes in vortex shedding behavior. This paper is focused on the identification of the physical reasons why the difference is occured in vortex shedding. The through flow velocity crossing fins decreases as increasing fin height and decreasing fin pitch mainly due to the flow resistence. Vortex shedding is affected strongly by velocity distribution around fin tube, especially by the velocity gradient. The velocity distribution at X/d=0.0 has lower gradient with increasing freestream velocity and fin height and decreasing fin pitch. Those differences in velocity gradients generate different vortex shedding mechanism.
톱니형 휜이 부착된 원주의 근접후류특성 연구 (Ⅰ) - 와유출 메카니즘의 특성변화 규명 -
류병남(Byong Nam Ryu),김경천(Kyung Chun Kim),부정숙(Jung Sook Boo) 대한기계학회 2002 大韓機械學會論文集B Vol.26 No.8
An experimental study is performed to investigate the characteristics of near wake behind a circular cylinder with serrated tins using the constant temperature anemometer and through now visualization. Previous report( Boo et al,. 2001) shows that there arc three different modes in vortex shedding behavior. This paper is focused on the identification of the physical reasons why the difference is occured in vortex shedding. The through now velocity crossing tins decreases as increasing tin height and decreasing fin pitch mainly due to the now resistence. Vortex shedding is affected strongly by velocity distribution around tin tube. especially by the velocity gradient. The velocity distribution at X/d=0.0 has lower gradient with increasing freestream velocity and tin height and decreasing tin pitch. Those differences in velocity gradients generate different vortex shedding mechanism.
夫禎淑,權大甲,尹焞鉉,李祥秀,李大吉 부산대학교 공과대학 1982 硏究報告 Vol.23 No.-
Two dimensional turbulent jet exhausting into a stationary atmosphere was studied experimentally by use of the linearized constant-temperature hot-wire anemometer. It was established that the jet was truly self-preserving about 40 slot widths, and the measurements were made up to 160 slot widths downstream of the nozzle. In order to get the two dimensional jet, the cubic equation suggested by Morel was used for the contraction curve of the nozzle. The uniformity of the jet velocity was well achieved and the turbulence intensities were low at the nozzle exit. It shows that the spreading rate was 0.094, and the turbulence intensities at the similarity region were u'/U_(m)=0.21, v'/U_(m)=0.18 and w'/U_(m)=0.16 respectively. When the nozzle exit velocity was vaired, it appeared that the starting point of the similarity region was moved to the nozzle for the low Reynolds number. The ratio of the entrance flow velocity to the center line velocity of the jet was about 0.07.
夫禎淑,林光烈,金德茁 부산대학교 공과대학 1982 硏究報告 Vol.24 No.-
The effects of flow velocity and the cavitation number on noise due to cavitation are investigated experimentally in this study. The velocity range covered is 5.2m/s to 6.4m/s. Tests are conducted with three triangular prisms as a cavitating source in a two dimensional water tunnel. For a fixed velocity, SPL measured in the high frequency range depends on the cavitation number. SPL at 8KHz increases to a peak and thereafter decreases to a constant value when the cavitation number is decreased continuously. At peak SPL conditions, the velocity exponets for intensity of noise are found to have approximate values of 10.34, 6.67, and 12.78 when the blockage ratio is 0.15, 0.25, and 0.35, respectively.