A simplified model of the interaction of the trawl warps, the otterboards and netting drag

Computational modelling is a valuable complementary tool to assess behavior of bottom trawl fishing gears. A simplified model of the interaction of the trawl warps, the otterboards and netting drag is proposed. The model does not calculate the net geometry and it is constrained to steady towing conditions, flat seabed and gear symmetry. Simulations provide a number of relevant outcomes such us distribution of tensions at the warp, balance of forces at the otterboards or horizontal spread under different haul conditions such as depth or towing speed. Based on the above, the objective of the present study was to describe and implement the model and thus to predict the consequences of changing some gear components, in particular to predict the impact of the doors on the seabed. This objective could have been fulfilled through extensive sea trials to cover all the different haul conditions of interest. Due to the high cost of such trials we chose to perform sea trials at two different bottom depths at which two towing speeds were tested. Then we applied the simulation software to make a preliminary comparison with experimental results and obtain predictions on what would be the effect of changing some gear components.

[1]  Fuxiang Hu,et al.  Effects of drag coefficient of netting for dynamic similarity on model testing of trawl nets , 2001 .

[2]  Chun-Woo Lee,et al.  Modeling of a midwater trawl system with respect to the vertical movements , 2000 .

[3]  Chun-Woo Lee,et al.  Physical modeling for underwater flexible systems dynamic simulation , 2005 .

[4]  Tadashi Tokai,et al.  Dynamic analysis of midwater trawl system by a two-dimensional lumped mass method , 1995 .

[5]  B. van Marlen,et al.  An empirical velocity scale relation for modelling a design of large mesh pelagic trawl , 1996 .

[6]  Finbarr G. O’Neill,et al.  Axisymmetric trawl cod-ends made from netting of a generalized mesh shape , 1999 .

[7]  D. Marichal,et al.  Study of the dynamics of submerged supple nets (applications to trawls) , 1998 .

[8]  Tsutomu Takagi,et al.  Validity and visualization of a numerical model used to determine dynamic configurations of fishing nets , 2003 .

[9]  A.J. Sorensen,et al.  Mathematical Modeling of the Hydrodynamic Forces on a Trawl Door , 2006, IEEE Journal of Oceanic Engineering.

[10]  Hae-Hoon Park.  A method for estimating the gear shape of a mid-water trawl , 2007 .

[11]  Michael T. Heath,et al.  Scientific Computing , 2018 .

[12]  F. G. O'Neill.  Small-scale modelling rules of trawl nets , 1993 .

[13]  Fuxiang Hu,et al.  A static analysis of the tension and configuration of submerged plane nets , 2002 .

[14]  Francois Theret.  Étude de l'équilibre des surfaces réticulées placées dans un courant uniforme : application aux chaluts , 1993 .

[15]  K. C. Watts,et al.  The otter board as a low-aspect-ratio wing at high angles of attack; an experimental study , 1986 .

[16]  C. K. H. Chin,et al.  A numerical model of a towed cable-body system , 2000 .

[17]  R. C. Weast.  CRC Handbook of Chemistry and Physics , 1973 .

[18]  Antonello Sala,et al.  Comparison between model testing and full-scale trials of new trawl design for Italian bottom fisheries , 2004 .

[19]  Alessandro Lucchetti,et al.  The influence of twine thickness on the size selectivity of polyamide codends in a Mediterranean bottom trawl , 2007 .

[20]  Odd M. Faltinsen,et al.  Sea loads on ships and offshore structures , 1990 .

[21]  Daniel Priour.  Analysis of nets with hexagonal mesh using triangular elements , 2003 .

[22]  G Niedzwiedz,et al.  Rope and net calculations applied to problems in marine engineering and fisheries research , 1998 .

[23]  Antoni Mànuel,et al.  Simulation of bottom trawl fishing gears. A simplified physical model , 2007 .