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천장호(Jang-Ho Chun),김문찬(Moon-Chan Kim),전호환(Ho-Hwan Chun),도인록(In-Rok Do),구자균(Ja-Kyun Koo) 한국해양공학회 2011 韓國海洋工學會誌 Vol.25 No.5
Recently, a ship-shaped barge has been developed to improve the resistance performance, as well as course-keeping capability. However, the stern of the barge is still similar to a box shape, and the vortex generated at the side of the barge creates drag and yaw instability. In order to solve this problem, stern skegs are normally used. The present paper deals with the correlation between the size of the stern skegs and the barge dimensions and hull coefficient. A stern skeg was designed to prevent yaw instability and minimize any additional resistance. The resistance test and course keeping test were performed in the towing tank at Pusan National University. To determine the correlation parameters between the designed stern skeg size and barge dimensions, a parametric study was also performed. Based on the experimental data from five barges, the optimum skeg dimensions were successfully derived. It is expected that the validation of the present study will be carried out by further experiments and computational comparisons in the new future.
대형 와 모사를 사용한 혼합 탱크 내의 농도장과 유동장의 동시 해석
윤현식,전호환,하만영,Yoon, Hyun-Sik,Chun, Ho-Hwan,Ha, Man-Yeong 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.9
Transport of a scalar quantity, such as chemical concentration or temperature, is important in many engineering applications and environmental flows. Here we report on results obtained from the large eddy simulations of flow and concentration fields inside the tank performed using a spectral multi-domain technique. The computations were driven by specifying the impeller-induced flow at the blade tip radius (Yoon et al.). This study focused on the concentration development at different molecular diffusivities in a stirred tank operated under turbulent conditions. The main objective of the work presented here is to study the large-scale mixing structure at different molecular diffusivities in a stirred tank by using the large eddy simulation. The time sequence of concentration and flow fields shows the flow dependency of the concentration development. The presence of spatial inhomogenieties is detailed by observing the time variation oflocal concentration at different positions.
대형 와 모사를 통한 레이놀즈 수 증가에 따른 혼합 탱크 내의 유동 구조의 연구
윤현식,전호환,하만영,Yoon, Hyun-Sik,Chun, Ho-Hwan,Ha, Man-Yeong 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.9
The stirred tank reactor is one of the most commonly used devices in industry for achieving mixing and reaction. Here we report on results obtained from the large eddy simulations of flow inside the tank performed using a spectral multi-domain technique. The computations were driven by specifying the impeller-induced flow at the blade tip radius. Stereoscopic PlY measurements (Hill et al. $^{(1)}$) along with the theoretical model of the impeller-induced flow (Yoon et al. $^{(2)}$) were used in defining the impeller-induced flow as superposition of circumferential, jet and tip vortex pair components. Large eddy simulation of flow in a stirred tank was carried out for the three different Reynolds numbers of 4000, 16000 and 64000. The effect of different Reynolds numbers is well observed in both instantaneous and time averaged flow fields. The instantaneous and mean vortex structures are identified by plotting an isosurfaces of swirling strength for all Reynolds numbers. The Reynolds number dependency of the non-dimensional eddy viscosity, resolved scale and subgrid scale dissipations is clearly shown in this study.