Study on the Control Performance of Midwater Trawl Net

研究开发了一种高度可控的中水拖网系统。采用水槽试验、现场试验和理论分析三种方法进行了试验研究，通过水槽试验，比较了采用帆布制成的新型网口张开器的水中拖网的静、动态特性，并对其性能进行了分析。结果表明，帆式中水拖网适合于低速拖网，因为其张口面积相对于网具总阻力在低速时较大。通过改变水流速度，比较了基于工作深度的两种中水拖网的控制性能。结果表明，在相同的漂浮或下沉距离下，帆布式作业船的作业深度控制所需的时间比水手式作业船的作业深度控制时间要短。现场试验是在日本东京水产大学的若佐…号R/V Shinyo-Maru上进行的1989年和1990年日本海的更多海湾。在不同拖速、不同翘曲长度下，观测了拖网作业深度、网口高度、翼展、绳索张力、网板深度等时间序列数据，并通过设计中水拖网净阻力的经验公式进行了理论分析。理论分析是基于R/V新洋丸的中水拖网系统。最后，建立了中水拖网系统动态特性随拖速变化的自回归模型，确定了模型中的未知参数。用统计方法证明了该模型的有效性。对该模型进行了计算机模拟，并与现场试验结果进行了比较。模型的中水拖网系统的动态特性与现场试验的结果基本一致。较少

A study to develop a midwater trawl system which is highly controllable was conducted. Three approaches were made to conduct the study namely ; flume experiment, field experiment and theoretical analysis.The flume experiment was conducted to clarity the performance of the midwater trawl net using a new net-mouth opening device made of canvas by comparing its static and dynamic characteristics to that of the otter type. It was observed that the canvas type midwater trawl net was suited to low speed towing because its mouth opening area relative to the total drag of the gear was high at low speed. The control performance of both types of midwater trawl based on the working depth was compared by changing the current speed. The result showed that the time required to control the working depth at the same floating or sinking distance was shorter for the canvas type than the otter type.The field experiment was conducted on board the R/V Shinyo-maru of Tokyo University of Fisheries at Wakasa … More Bay in Japan Sea in 1989 and 1990. The time series data of the working depth of the net, the height of the net-mouth, the wing spread, the tension fo the bridle, the depth of the otter boards, etc. were observed at variable towing speed and warp length.The theoretical analysis was done by designing an experimental formula for calculating the net drag of the midwater trawl. The theoretical analysis was based on the midwater trawl system of the R/V Shinyo-maru. Good agreement was obtained between the experimental and the theoretical results.Lastly, an autoregressive model to estimate the dynamic behavior of midwater trawl system by varying the towing speed was built and unknown parameters in the model were determined. The validity of the present model was statistically proven. A computer simulation was made on the model to compare it with the results of the field experiment. Similar characteristics of the dynamic behavior of the midwater trawl system for the model and the field experiment was obtained. Less