Model Experiments on the Physical Characteristics of the Thai Shrimp Trawl Gear

中尾佐助教授退官記念号This study was carried out in order to obtain some fundamental information on the physical characteristics of the balloon type single rigged Thai shrimp trawl gear in a circular tank. The reduced scale model net was constructed on Dr.Tauti's comparative method. Observations and measurements were made simultaneously on the shape and resistance of the net under the influence of six stages of flow velocity. For convenience of discussion, all empirical values from the reduced scale model have been converted into full scale values. The results obtained in this study are summarized as follows:1) Five parameters i.e. net mouth height (H), wing tip distance (W), sweeping area (Sa), projective area of net mouth (An) and water filtering volume (Fv) were taken into account to determine the physical characteristics of the gear. The above mentioned parameters are formulated as follows:H=2.01 V^<-0.76>W=5.85 V+7.6Sa=17.9 V-3.4An=-17.0 V^<3>+68.4 V^<2>-86.0 V+57.0Fv=21.3 V+3.22) Concerning the fluid dynamical resistance of the gear under towing conditions, the obtained results of total net resistance (Rt), net resistance (Rn) and otter board resistance (Rob) are formulated as follows:Rt=665.55 V^<1.9>Rn=449.62 V^<1.5>Rob=114.45 V^