Flow-induced vibration reduced-order model of fuel rods based on large eddy simulation and a self-developed MATLAB-based Euler-Bernoulli beam element

: Understanding the flow-induced vibration (FIV) behavior of fuel rods is essential for ensuring the safe and reliable operation of nuclear reactors, yet conventional high-fidelity simulations are often prohibitively time-consuming and computationally expensive. To address this challenge, this study develops an efficient and portable fluid–structure interaction (FSI) model that integrates high-fidelity turbulent excitation forces obtained from Large Eddy Simulation (LES) in FLUENT with an independently developed Euler-Bernoulli beam element model implemented in MATLAB. By partitioning the fuel rod surface into multiple wall sections and applying parallel computation of concentrated forces through user-defined functions (UDFs), the model accurately captures turbulent excitation forces while achieving over 20-fold higher efficiency than commercial software. Structural responses can be computed within about one minute without compromising accuracy. Applying this model to fuel rods in water and lead-bismuth eutectic (LBE) shows that LBE reduces the dominant vibration frequency by 32% and increases the root-mean-square (RMS) displacement by more than tenfold compared to water. These results demonstrate that the newly developed Euler-Bernoulli beam model, when coupled with high-fidelity flow field data, provides a fast and accurate tool for predicting FIV responses, offering valuable support for safety assessment and design optimization of nuclear reactor systems, especially those employing liquid metal coolants.