Analysis of Power Spectrum Density in the PWR Fuel Assembly Using the 3-D LES Turbulent Model of Fluent 6
Analysis of Power Spectrum Density in the PWR Fuel Assembly Using the 3-D LES Turbulent Model of Fluent 6
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DOI：
10.1115/icone12-49297
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发表时间：
2004
期刊：
影响因子：
--
通讯作者：
Hyeun-Min Kim;H. No
中科院分区：
文献类型：
--
作者：
Hyeun-Min Kim;H. No
Trublence-induced vibration is an important concern in the design of the spacer grids of nuclear power plants. This study addresses numerically and statistically the effects of random pressures due to turbulent flows upon the fluctuating responses to the power spectrum density in one-dimensional nuclear fuel rod supported simply by the spacer grids. The dynamic forces produced by the pressure fluctuation on the rod surface are calculated by the 3-dimensional large eddy simulation turbulent model in Fluent 6 to simulate the flow field in the same as being measured empirically via pressure transducers. To acquire response to fluctuating pressure, the mode response equation of vibration is used in case of a cylindrical rod in one-dimensional case. The first modal longitudinal joint acceptance integral including a coherence function is also an important parameter affecting the displacement in the form of the r.m.s. of modal responses along with the damping ratio. The root mean square of the lateral displacement in addition to the natural frequency is studied using the PSD and the longitudinal joint acceptance integral in a fundamental mode. The random pressure PSD on the middle point of the rod shows the typical turbulence pattern: the PSD energy decreases slightly in a low frequency region, but decreases rapidly and linearly with frequency as the frequency exceeds a certain value. The PSD in a very high frequency region is obtained assuming the slope is constant in a logarithmic graph after smoothing the PSD. It turns out that the r.m.s. displacement ranges from 15 to 40 micro-meter at the maximum value using the mode response equation under the modal damping ration ranging from 0.01 to 0.05.Copyright © 2004 by ASME
