• Tunnel and Underground Space
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• v.9 no.3
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• pp.185-193
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• 1999

This paper presents results of dynamic analysis for a bridge in intersection part of two tunnels subjected to moving vehicle load. Since such a bridge system is very unusual due to the fact that it is located in tunnel, the dynamic characteristics of the structure can not be assumed as conventional one. The structure investigated in this study it a reinforced concrete bridge in the intersection part of Namsan Tunnel-1 and Tunnel-2 in Seoul. It is supported by temporary steel structure which shall be constructed during the period of replacing lining in Tunnel-2. Dynamic analysis was carried out for the system using a finite element model constructed by general purpose FE program SAP2000. For this purpose, the structure, lining of tunnels, and surrounding rock were represented by finite elements, while the rock region it truncated and on its outer boundary viscous dampers were placed to simulate radiation of elastic waves generated tunnels. Several types of vehicle with various driving velocities were considered in this analysis. The FE model including vehicle loadings was verified by comparing calculated peak particle velocity with the measured one. From the analysis, the impart factor for the bridge was estimated as 0.21, which indicates that the use of upper bound for the impact factor in design code is reasonable for this kind of bridge system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.11
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• pp.7990-8000
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• 2015

Plant factories are plant cultivation systems which produce farm products uniformly under the controlled environmental condition regardless of seasons and places. Thermal flow in the plant factory is an important parameter in cultivating plants. In this research, we study thermal flow characteristics for a hybrid plant factory with multi-layer cultivation shelves using computer simulation techniques. In order to obtain numerical solutions for thermal flow characteristics, a finite volume method was applied. We consider a low-Reynolds-number ${\kappa}-{\epsilon}$ turbulence model, incompressible viscous flows, and pressure boundary conditions for numerical simulation. Commercial software Solid Works Flow Simulation is then used to investigate characteristics of thermal flows in the plant factory applying several different inflow air velocities and arrangements of cultivation shelves. From numerical analysis results, we found that temperatures in cultivation shelves were uniformly distributed for Case 3 when the inflow air velocity was 1.6 m/s by using a blower in the plant factory. However in Case 1 lower temperature distributions were observed in test beds, TB2 and TB3, which indicated that additional temperature control efforts would be required. Average shelf temperature increased by $3^{\circ}C$ using artificial light source (DYLED47) with 50% blue and 50% red LED ratios. Korea Academia-Industrial cooperation Society.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.10
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• pp.618-627
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• 2016

This study numerically analyzes the characteristics of the velocity distribution for each location of a square-sectional $180^{\circ}$ bent duct using a Reynolds Stress Turbulent model. The flow parameters were varied, including the working fluids, inlet velocity, surface roughness, radius of curvature, and hydraulic diameter. The boundary conditions for computational fluid dynamics analysis were inlet temperatures of air and water of 288 K and 293 K, inlet air velocity of 3-15 m/s, inner surface roughness of 0-0.001 mm, radius of curvature of 2.5-4.5 D, and hydraulic diameter of 70-100 mm. The working fluid characteristics were highly affected by changes in the viscous force. The maximum velocity profiles in the bent duct were indicated when the $90^{\circ}$ section was in the region of X/D=0.8 and the $180^{\circ}$ section was in the region of Y/D=0.8. Lower surface roughness and higher radius of curvature resulted in a higher rate of velocity change. Also, an efficient measuring location downstream of the bent duct is suggested since the flow deviations were the most stable when the straight duct length was in the region of L/D=30. The minimum deviations at the same velocity conditions according to the hydraulic diameter were mostly indicated in the range of L/D=15-30 based on the standard deviation characteristics.