The behaviour of net panels with bending stiffness is dependent on the stiffness and potentially also the density of the material when exposed to oscillatory motions. This needs to be taken into account when net cages are product certified according to NS9415 (Standard Norge 2009). Experiments using two different net panels with bending stiffness were conducted to investigate the behaviour of nets with bending stiffness in oscillatory motion. For low oscillation frequencies the panels moved in a close to rigid body manner. When the oscillation frequencies where increased, however, there was a distinct difference between the copper and the Polyethylene Terephthalate (PET) nets, with a significant increase in the resulting oscillation amplitude for the copper net and a decrease for the PET net.
The proposed numerical model predicts this behaviour well in terms of oscillation amplitudes. It is, however, important to establish good estimates of the net panels bending stiffness in advance, particularly if product certification is the purpose of the numerical analysis.
Numerical analysis of rotation of a rigid body subject to the sum of a constant and dissipative moment