Abstract Spacer grid with mixing vane had been widely used in nuclear reactor core. One of the main feather of spacer grid with mixing vane was that strong swirl flow was formed after the spacer grid. The swirl flow not only changed the bubble generation in the near wall field, but also affected the bubble behaviors in the center region of the subchannel. The interaction between bubble and the swirl flow was one of the basic phenomena for the two phase flow modeling in fuel assembly. To obatin better understanding on the bubble behaviors in swirl flow, full three dimension numerical simulations were conducted in the present paper. The swirl flow was assumed in the cylindral calculation domain. The bubble interface was captured by Volume Of Fluid (VOF) method. The properties of saturated water and steam at different pressure were applied in the simulation. The bubble trajectory, motion, shape and force were obtained based on the bubble parameters captured by VOF. The simulation cases in the present study included single bubble with different size, at different angular velocity conditions and at different pressure conditions. The results indicated that bubble migrated to the center in swirl flow with spiral motion type. The lateral migration was mainly related to shear stress magnitude and bubble size. The bubble moved toward the center with high velocity when the swirl magnitude was high. The largest bubble had the highest lateral migration velocity in the present study range. The effect of pressure was small when bubble size was the same. The prelimenery simulation result would be beneficial for better understanding complex two phase flow phenomena in fuel assembly with spacer grid.

中文翻译：

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基于流体体积法的涡流单气泡动力学初步数值研究

摘要 混合叶片隔栅已广泛应用于核反应堆堆芯。带混合叶片的隔栅的主要特点之一是隔栅后形成了强烈的涡流。旋流不仅改变了近壁场气泡的产生，而且影响了子通道中心区域的气泡行为。气泡和涡流之间的相互作用是燃料组件中两相流建模的基本现象之一。为了更好地理解涡流中的气泡行为，本文进行了全三维数值模拟。在圆柱计算域中假设涡流。气泡界面通过流体体积 (VOF) 方法捕获。模拟中应用了不同压力下饱和水和蒸汽的特性。基于VOF捕获的气泡参数获得气泡的轨迹、运动、形状和力。本研究中的模拟案例包括不同尺寸、不同角速度条件和不同压力条件下的单个气泡。结果表明，气泡以螺旋运动型旋流向中心迁移。横向迁移主要与剪切应力大小和气泡大小有关。涡旋强度大时，气泡向中心高速移动。在目前的研究范围内，最大的气泡具有最高的横向迁移速度。当气泡大小相同时，压力的影响很小。