Study of flow-induced vibrations of spiral tube bundles under nonlinear support in lead-bismuth eutectic environment based on large eddy simulation

The flow-induced vibration (FIV) phenomenon of multi-row helical tube bundles in lead–bismuth eutectic (LBE) environments may be more severe with the tube-support gap included. This study utilizes the large eddy simulation (LES) turbulence model and a nonlinear dynamics model to investigate the effects of contact types, tube-support gaps, and the number of supports on the FIV characteristics of spiral tube bundles in LBE environment. The reliability of the numerical model is confirmed through validation against existing experimental data. The results show that, in the absence of gaps, linear and nonlinear contact conditions have a negligible impact on vibration characteristics. However, the influence of these contact types becomes significant when gaps are present. The presence of the gap causes a reduction in the critical flow rate at which fluid-elastic instability occurs and significantly alters the vibration characteristics during instability so that it no longer vibrates at the natural frequency of the structure. For flutter vibrations, the frequency domain characteristics of dynamic parameters remain consistent. For non-flutter vibrations, the displacement root mean square (RMS) is proportional to the gap size before support failure. As the gap increases (0 ∼ 0.5 mm), the contact pressure RMS decreases monotonically, while the destructiveness caused by contact vibro-impact initially increases and then decreases. The structural stress at the tube-support exhibits a trend of first decreasing and then increasing as the gap size grows. Additionally, increasing the number of supports (2 ∼ 4 within 90°) significantly reduces the vibration displacement and stress levels of the spiral tube.