中文摘要：

核燃料组件导向管底部泄流孔的水力损失系数对控制棒落棒时间和落棒速度有着重要影响。在落棒问题分析中,能否采用叠加理论计算泄流孔的水力损失,必须进行具体分析和论证。采用CFD方法对＂突缩-突扩＂型和＂突缩-突缩＂型两类四种泄流孔在不同流速下的水力损失进行了数值模拟计算,并与理论计算结果进行了对比。计算结果表明,对于流道内未充分发展的流动,理论计算结果与数值模拟计算结果存在一定差异。

英文摘要：

Hydraulic loss coefficient of bottom drain hole of the guide tube of the nuclear fuel assemblyhas has important influence on the drop-time and the drop-speed of the control rod. In rod drop analysis,it is necessary to make a concrete analysis and demonstrate whether the hydraulic loss of the drain hole can be calculated by the classical superposition theory.The hydraulic losses of＂sudden contraction-sudden expansion＂and＂sudden contraction-sudden contraction＂two types,four kinds of drain holeat different flow velocities were calculated by CFD method,the results of which were compared with those of the theoretical calculation. The calculation results show that there are some differences between theoretical calculation and numerical simulation results.