Numerical simulation of the fluid–structure interaction for two simple fuel assemblies

The fluid–structure interaction (FSI) for two simple fuel assemblies is studied by numerical method to remedy the deficiencies of theoretical and experimental methods. All the rods are considered as cylinders, modeled by Euler–Bernoulli beams, and are free to vibrate in any transverse directions. The FSI is simulated by the explicit partitioned scheme, in which the flow and structure solvers exchange the data within one time step to implement their coupling for FSI. The flow solver is the commercial CFD software Fluent and the structure solver is in-house developed beam solver, which is integrated into Fluent by the user-defined functions. The effects of dimensionless flow velocity and the number of cylinders on the dynamics of the fuel assemblies are investigated in detail. For small dimensionless flow velocity, the strong vibration is damped into weak oscillation induced by turbulence. If the dimensionless flow velocity is large enough, the buckling instability occurs. Increasing the number of cylinders in the fuel assembly promotes the occurrence of buckling instability. These are consistent with the existing theoretical and experimental results.

► The FSI of two simple fuel assemblies is studied numerically.
► The strong vibration is damped for small dimensionless flow velocity.
► The buckling instability may be induced for large dimensionless flow velocity.
► Increasing the number of cylinders promotes the occurrence of buckling instability.