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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.
대수 레이놀즈 응력모델에 의한 단이 진 벽면분류에 대한 수치해석
서호택,부정숙,Seo, Ho-Taek,Bu, Jeong-Suk 대한기계학회 2000 大韓機械學會論文集B Vol.24 No.12
Algebraic Reynolds Stree (ARS) model is applied in order to analyze the turbulent flow of wall-attaching offset jet and to evaluate the predictability of model. The applied numerical schemes are the upwind scheme and the skew-upwind scheme. The numerical results show a good prediction in the first order calculations(i.e., reattachment length, mean velocity, pressure), however, slight deviations in the second order(i.e., kinetic energy and turbulence intensity). Comparing with the previous results using the k-$\varepsilon$ model, the ARS model predicts better than the standard k-$\varepsilon$ model, however, slightly worse than the k-$\varepsilon$ model including the streamline curvature modification. Additionallay this study can reconfirm that the skew-upwind scheme has approximately 25% improved predictability than the upwind scheme.
대전지역 상수도 물의 계절변화에 따른 물리화학적 불균질
이현구,이찬희,서호택 대한자원환경지질학회 2000 자원환경지질 Vol.33 No.6
This study was undertaken to provide a drinking water quality on the basis of physicochemical properties. In this study, the 25 samples of supply waters of the Taejon area were sampled twice (February and August in 1999). Hydrochemistry of the supply water belongs to the $Ca^{2+}$-${HCO_3}^{-1}$ type, whereas the supply water was characterized by the relatively significant enrichment of ${Ca}^{2+}$, ${Na}^{2+}$, ${K}^{2+}$, ${Cl}^{2+}$ ions and heavy metals compared to the original water from the Daecheong lake. Generally, the supply water has a mean values for $10.7^{\circ}C$ of temperature, 6.86 of pH, -12 mV of Eh, 88 ${\mu}S$/cm of EC and 70.379 mg/l of TDS in February, whereas the waters of the same sites in August are a slightly high temperature ($26.1^{\circ}C$), TDS (78.069 mg/l) and extremely high EC (442 ${\mu}S$/cm) value. These values are similar with physicochemical properties of the original lake water depending on the seasonal differences. Results of speciation calculation indicate that potentially toxic ions might exist mainly in the forms of free metal (${Cu}^{2+}$ or ${Zn}^{2+}$) and a small amount of ${CO_3}^{2-}$and ${OH}^{-}$in the supply water. The water seemed to be in equilibrium with kaolinite field of the normal stability diagrams for the natural water. Based on enrichment parameter of the supply water normalized by original lake water composition, the average value of those parameter can be calculated with nearly 1.00, but the those values for Cu+Zn possible source of decrepit pipe lines are 126.75 in February and 115.63 in August samples. The parameter values varied with sampling sites, however, do not exceed by chemistry of drinking water standard. Solid compounds remained on the membrane filter papers after filtration are adhered to pale yellow or yellowish brown colored dissolved solids and precipitates, which are coated by 0.02 to 0.35 mm thick per 500 ml with colloidal particles of about 1 to 2${\mu}m$ size. The particles are mainly Fe-Cu-Zn compounds and partly detected to Mn and Pb.
尹焞絃,夫禎淑,徐鎬澤 부산대학교 공과대학 1987 硏究報告 Vol.33 No.-
Numerical calculations for the two dimensional reattachment jet flow fields having offset ratio 2.5 were done by skew upwind scheme method and compared with experiments. The standard and modified k-ε models are used as turbulence models and the modified one is considered the streamline curvature effect and preferential dissipation. In experiments, the nozzle exit velocity is 30m/s and the turbulent intensity is 0.2% at the nozzle exit. The reattachment length in the calculated results by the modified k-ε model has 3% error with the experiment. And the modified k-εmodel is better than the standard one for prediction the mean velocity field and static pressure field in this case.