Numerical investigation of vortex-induced vibration of a triple-pipe bundle

Pipe bundles are commonly observed in offshore oil and gas engineering. In this work, the vibration response of a typical triple-pipe bundle with cylinders arranged in a row in size order is examined numerically. The unsteady Reynolds-Averaged-Navier-Stokes equations and shear stress transport k-ω turbulence model coupling with an improved fourth-order Runge-Kutta method are employed to capture the fluid flow over the structure and the vibration response of the oscillator with varying reduced velocities ranging from 3.0 to 18.0. The numerical results indicate that the vibration response undergoes dramatic changes when the isolated cylinder is changed to be a bundle. The in-line amplitude has an obvious increase due to the great fluctuation of pressure difference and shear stress of the bundle. However, the cross-flow amplitude of the bundle is smaller than the single cylinder at a certain flow velocity range, exhibiting a good suppression effect. The separation of boundary layer moving back and the narrow wake can illustrate this effect. The vortex structure of the bundle varies with the change in flow velocity, and the vortices are scatted and unstable. Therefore, the bundle oscillates in an irregular motion and its motion in turn affects the vortex shedding.