A Reduced-Order Model of Mode Characteristics and Flow-Induced Vibration Response of Fuel Rod Based on POD Method

A Reduced-Order Model (ROM) for swiftly predicting both the modes and flow-induced vibration response of fuel rods is introduced in this study. Firstly, modes for fuel rods with varying stiffness are obtained using ANSYS-Batch, and these modes are then compiled into a Snapshots matrix. Subsequently, leveraging MATLAB and semi-empirical formulas, the flow-induced vibration responses of fuel rods are batch-calculated, and the resulting data is assembled into another Snapshots matrix. The Proper Orthogonal Decomposition (POD) method is then applied to project the Snapshots matrix into a lower-dimensional space, with the POD modes having the highest energy contribution being selected based on the magnitude of eigenvalues. Finally, the Snapshots matrix is reconstructed back into physical space using the selected POD modes, enabling the rapid calculation of both mode and flow-induced vibration responses. Our study reveals that for reconstructing the first-order mode and flow-induced vibration responses, a smaller stiffness necessitates a greater number of POD modes. Furthermore, in the reconstruction of different-order modes with the same stiffness, higher-order modes require a greater number of POD modes. The findings of this study hold significance for the swift calculation of fuel rod mode characteristics and flow-induced vibration responses.