Hydrodynamic responses of a large flexible net swinging in waves

Abstract

In deep-sea aquaculture cages, large flexible nets are usually mounted on the steel frames of aquaculture cages, which are easily broken. When a cage vibrates over time, the flexible nets also oscillate, causing relative motions with respect to fluid flows. This study focuses on the hydrodynamic behaviors of a large flexible net swinging in waves, in which three different types of swings are simulated with the swing center located above, on, and below the net, respectively. The incoming waves are simulated using the Airy wave theory. The nonlinear vibrations of the flexible net in three dimensions are solved using the lumped-mass method. The influences of swing amplitudes and frequencies on the vibrations of the net are analyzed in detail. It can be known that with the increase of swing amplitude, the vibration displacements of the net in the horizontal direction decrease, while they increase in the vertical direction. Furthermore, the dynamic tensions of net twines increase as the swing angular frequency rises.