Model test of trawl gear with a net-mouth opening device based on modified Tauti's law

Abstract

For model testing of trawl gear utilizing an opening device such as an otter board, the ratio in area of the model opening device to the full-scale device was proposed based on modified Tauti's law. A sea trial with a full-scale midwater trawl net of 27.44 m in total length and model experiment with 1/10 scale model were conducted. Two otter board models of different scale were used for the model experiment: otter board model I of 1/60 area scale based on the modified Tauti's law, and model II of 1/100 area scale based on the original Tauti's law. As a result, a distinct difference both in the distance of the two otter boards and in net-mouth height was found between the converted values from the model test with model II based on Tauti's law and the observed values in the full-scale sea trial. In contrast, no such difference was observed in the results of model I. In addition, it was verified that the speed ratio based on the modified Tauti's law was useful for predicting the drag of the test trawl gear with opening device.