The effect of the presence of slits in the wall of the outer one of two concentric cylinders involved in creating a Taylor-Couette flow is experimentally investigated. Three models with different numbers of slits (6, 9 and 18) are used and the radius ratio and aspect ratio of the models are 0.825 and 48, respectively. The velocity fields are measured by using the digital particle image velocimetry method, and the refractive index matching technique is applied to remove image distortion. The flow regime in the Taylor-Couette flow is studied by increasing the Reynolds number. The results show that the presence of slits does not affect the laminar transition process and that the transition to turbulent Taylor vortex is accelerated as the number of slits increases.

The selective catalytic reduction method is a useful method for the denitrification process of exhaust gas emitted from industrial facilities. The distribution of the ammonia–nitrogen oxide mixing ratio at the inlet of the catalyst layers is important in the denitrification process. In this study, a computational analysis technique was used to improve the uniformity of the NH3/NO molar ratio by controlling the flow rate of the ammonia injection nozzle according to the flow distribution of nitrogen oxides in the inlet exhaust gas of the denitrification facility. The application model was simplified to the two-dimensional array adopted from the existing selective catalytic reduction (SCR) process in the large-scaled coal-fired power plant. As the inlet conditions, four (4) types of flow pattern were simulated, i.e., parabolic, upper-skewed, lower-skewed, and random. The flow rate of the eight (8) nozzles installed in the ammonia injection grid was controlled by Design Xplorer as the optimization tool. In order to solve the two-dimensional steady, incompressible, and viscous flow fields, the commercial software named ANSYS Fluent was used with the κ-ε turbulence model. The root mean square of NH3/NO molar ratio at the inlet of the catalyst layer has been improved from 84.6% to 90.1% by controlling the flow rate of the ammonia injection nozzles. From the present numerical simulation, the operation guide could be drawn for the ammonia injection nozzles in SCR DeNOx facilities.

Key Words：Turbulent kinetic energy(난류 운동 에너지), Adverse pressure gradient(역압력 구배), RANS equations(RANS 방정식), SST k-ω model(SST k-ω 모델), -f model(-f 모델) Abstract：The flow characteristics on the periodically arranged semi-circular ribs in a rectangular channel for turbulent flow have been investigated numerically. The aspect ratio of the rectangular channel was AR=5, the rib height to hydraulic diameter ratio was 0.07 and rib height to channel height ratio was e/H=0.117. The v2-f turbulence model and SST k-ω turbulence model were used to find the flow characteristics of near the wall which are suited for realistic phenomena. The numerical analysis results show turbulent flow characteristics and pressure drop at the near the wall as observed experimentally. The results predict that turbulent kinetic energy(k) is closely relative to the diffusion of recirculation flow. and v2-f turbulence model simulation results have a good agreement with experimental.

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