A cod-end is the rearmost part of a trawl fishing gear that
collects the catch during the towing. The shape of cod-ends
is of importance as it determines mesh opening and consequently
influences the selectivity of fish from the cod-end.
The project considers two different numerical models of
the cod-end deformation: the axis-symmetric model and
the 3D finite element model based on the triangular elements.
The models are described and implemented in the
C# code using the principles of object-oriented programming.
Different solutions for improving the convergence of
the Newton-Raphson method that is commonly used to find
the equilibrium shape of the cod-end models are presented
and compared. The numerical results from the two models
are compared. A flume tank experiment is performed with
a motion tracking system to sample the cod-end shape in
3D. The results suggests a good correspondence between the
models for the small scale cod-ends with thin twines.