The coupled vibrations of a rectangular frame and a flexible net subjected to waves and currents

Abstract

Aquaculture cages are commonly used to culture fish in the open sea. The main structure of these cages consists of steel pipe frames. The frames are covered with flexible nets. Under the action of waves and currents, the frames and flexible nets may vibrate simultaneously. There is a dynamic interaction between them. In this paper, a rectangular frame is modeled using the Euler-Bernoulli beam theory, and the flexible net is simulated using the lumped-mass method. The hydrodynamic forces on the frame and net caused by waves and currents are calculated using Morison’s equation. A three-dimensional dynamic coupled model of the frame and flexible net is developed. The dynamic model is solved using numerical methods. After verifying the dynamic model, detailed analysis is conducted on the dynamic interactions between the frame and flexible net. The results show that under the action of waves and currents, the vibration amplitudes of the frame and flexible net become larger due to the interactions between them, while their vibration frequencies seldom change.