Verification of the catenary-application to the warp of a trawl considering the weight of the gear

漁具重量を考慮した場合の曳網索へのカテナリー理論適用

Verification of the catenary-application to the warp of a trawl considering the weight of the gear

Creators Inoue Satoru

Creators Tada Akira

Creators Nagamatsu Kimiaki

Many methods have been used to determine the shape approximation of the warp of a trawl. The catenary approximation is one of them. Therefore, in the previous paper, we verified the catenaryapplication to the warp of a towed net under various conditions using a circulating water tank. However it was carried out under a simple condition, that is, not considering the weight of the gear. Therefore in this paper, we verified the catenary-application incorporating the weight of the gear to the warp of a trawl net. We used a cord weighted with lead weights and a cone net as the actual warp and a towed. net as before. We newly attached lead weights to simulate the weight of the gear to the cone net. In the tank, we took photographs of the cord in the flow, changing the lead weights, the length and the weight of the cord and the velocity of the flow. From the photographs we measured the depth of the net. We also calculated the depth by the rectified catenary and compared it against the measured depth. Furthermore in a shipboard trial, we calculated the depth by the rectified catenary and compared it against the measured depth of an actual trawl. In both tank and on-board assessments, the variance between the measured depth and the calculated depth was small. Therefore it is considered that the current verification of the rectified catenary-application to the warp of a trawl is appropriate.

[ISSN]0370-9361