In lead-bismuth cooled fast reactors, the high-density liquid metal coolant and rapid flow characteristics introduce flow-induced vibration (FIV) risks to wire-wrapped fuel assemblies. Accurate prediction of FIV behavior is essential for assessing structural integrity.

This study aims to establish a robust numerical framework for analyzing FIV in wire-wrapped fuel rods and evaluate turbulence modeling approaches.

Based on the ANSYS (Analysis System) platform, a flow-structure interaction (FSI) model was developed for a single wire-wrapped fuel rod. The applicability of the SST k-ω and large eddy simulation (LES) turbulence models was systematically compared. Sensitivity analyses were conducted for flow-solid coupling methods, including both unidirectional and bidirectional coupling. A meshing strategy was proposed to determine appropriate dimensions for the turbulence models, with sensitivity analyses performed for mesh density and time step size. Finally, the FSI model was verified by experimental data and empirical formula.

The comparison results indicate that the LES model can more accurately captures wall pressure fluctuations on the fuel rod whilst the one-way coupling method satisfies accuracy requirements for micrometer-scale vibration problems. Analysis of the seven-rod bundle model reveals that helical wire spacers cause uneven flow distribution in the flow channel while the vibration displacements of the central rods (10 μm and 40 μm) are significantly smaller than those of the surrounding rods (50 μm). The vibration is dominated by the first-order frequency without resonance, characteristic of turbulent excitation.

This study provides a reliable basis for rheological vibration analysis of wire-wrapped fuel in lead-bismuth fast reactors, offering significant implications for engineering design and safety assessment.