CFD analysis and experiment on turbulent flow with and without a fuel-assembly spacer grid by FLUENT and LDA = Fluent와 LDA를 이용한 핵연료 봉다발 지지격자가 난류유동에 미치는 영향에 관한 CFD 연구와 실험

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The effect of a fuel-assembly spacer grid on turbulence flow was studied by a numerical and an experimental method. The computational fluid dynamics analysis was performed to investigate an optimized computational domain, supporting spring and wall thickness effect, and mixing vane effect and to validate experimental results. Three types of channels, 2×2, 3×3 and 4×4 for IFM (Intermediate Flow Mixing) spacer grid and a 5×5 channel for a hybrid spacer grid were simulated using the FLUENT code. The measurements on turbulent flow through a 5×5 hybrid spacer grid in water were performed using LDA (Laser Doppler Anemometry) to obtain local velocity, turbulence intensity and pressure drop, and a fuel rod vibration was measured using a vibrometer. A hollow glass spheres with the diameter of 10㎛ were added to water as seeding particles for a better signal response. The standard k-ε model and the unstructured mesh were used in the CFD simulation. The boundary condition of outlet was selected as outflow option, and that of side was selected as symmetry option in FLUENT. The number of mesh was 2,401,411 for a 4×4 IFM spacer grid, and 3,402,338 for a 5×5 hybrid spacer grid. As the convergence criterion $10^{-3}$ was used for all flow variables. It was shown that the minimum channel number was a 4×4 channel for the prediction of local flow variables in the case of the simulation of a real fuel assembly whose channels were not periodic. The various flow-comparison factors were reviewed and proposed for the analysis of the effects of a spacer grid. The turbulent-related factors increased rapidly through the spacer grid and rapidly decreased downstream the spacer grid, and the swirl-related factors also increased rapidly and decreased more slowly than the turbulent-related factors. The effect of the supporting spring was very significant near the spacer grid for axial velocity change. The pressure drop by the spacer grid was estimated to be about two times of the pressure dr...
NO, Hee-Cheonresearcher노희천researcher
한국과학기술원 : 원자력및양자공학과,
Issue Date
177053/325007 / 020003304

학위논문(석사) - 한국과학기술원 : 원자력및양자공학과, 2002.8, [ xi, 84 p. ]


LDA; FLUENT; mixing vane; spacer grid; flow-induced vibration; 회전유동; 유동기인진동; 난류; 봉다발; 지지격자

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