Large Eddy Simulation of Fluid–Structure Interaction for Two Elastic Cylinders in Axial Flow

The axial-flow-induced vibration (AFIV) of fuel rods in the nuclear power plant is closely related to nuclear safety. In this article, a numerical study of two elastic cylinders arranged side by side in axial flow is performed using the two-way fluid–structure coupling simulation. Large eddy simulation (LES) is employed to predict the turbulent flow. The root-mean-square (rms) vibration amplitude of the cylinder and the critical velocity of buckling instability are found to be in good agreement with experimental data. The vibration of two cylinders in axial flow are simulated at different dimensionless velocities u* ranging from 1.20 to 6.20, turbulence intensity Tu and space ratio P/D. Results show that at low Tu (0.7%), when u* reaches 4.56, both cylinders start to bend outward while vibrating. At higher Tu (2.9 and 5.0%), the two cylinders recover from the outward bending positions. Although Tu significantly affects the amplitude of cylinders, it does not change the vibration frequency of the cylinder and the critical velocity at which buckling instability occurs. As the gap is sufficiently small, the vibration amplitude does not show considerable variation laterally but enhances significantly along the centreline direction.