基于改进3D-R树的流固耦合模拟网格插值研究

流固耦合模拟是反应堆数值模拟的重要研究内容，针对数值堆CVR10热工水力软件PACA和结构力学软件HARSA网格不匹配、网格量巨大、网格单元还原困难，本研究利用3D-R树索引大规模流体域网格节点，完成了对固体域网格节点的插值计算。由于流体域网格节点密度大且分布较均匀，采用体积均分方式设计新结点分裂策略。对于溢出的结点，首先计算其最佳分割轴，即分裂后新结点体积和最小，假设为x轴；让垂直于x轴的分割面均分此结点；将分割面左侧孩子插入新结点N₁，右侧孩子插入N₂，其他孩子插入新增体积最小的N₁或N₂。用PACA和HARSA验证插值效率，结果表明改进3D-R树的插值效率明显高于3D-R树和传统插值。用HARSA对插值结果进行了固体流致振动计算并用Archard模型对固体振动进行了磨损评估。

Mesh Interpolation of Fluid-structure Interaction Simulation Based on Improved 3D-R Tree

Fluid-structure interaction simulation is an important research content of reactor numerical simulation. Based on the characteristics of thermal hydraulic software PACA and structural mechanic software HARSA of CVR1.0 (China virtual reactor), mesh mismatch, huge number of mesh and difficult to restore mesh cells, 3D-R tree was used to index large-scale fluid domain mesh nodes to complete the interpolation calculation of solid domain mesh nodes. In view of the high density and relatively uniform distribution of fluid domain mesh nodes, a new node splitting strategy of 3D-R tree was designed by using volume averaging method. In the new strategy, for the overflow node, the best split axis will be calculated firstly, and the best split axis can ensure that the sum of the new nodes volumes after splitting is the smallest, assuming that it is the x-axis. The node is divided equally by the split plane perpendicular to the x-axis. Child on the left of the split plane is inserted into new node N₁, child on the right of the plane is inserted into N₂, and other nodes are inserted into N₁ or N₂ with the smallest increasing volume. The interpolation efficiency is verified by PACA and HARSA. Experiments show that the interpolation efficiency of the improved 3D-R tree is significantly higher than that of the 3D-R tree and traditional interpolation method. Furthermore, HARSA was used to calculate the solid flow-induced vibration, and Archard model was used to evaluate the solid wear.