ソコビキアミ ノ ケンキュウ IV : オオガタ フクロアミ ノ エイモウ ジッケン

The measuring of the current velocity and resistance inside and outisde the drag net was carried out in the big sized drag net towed actually in the open sea. In the drag net, the length was 6.1 m; the ratio between the diameter of a twine (d mm) and the mesh size (l mm), namely d/l=0.021. The results obtained areas follow: a) The current velocity inside the net body (v m/sec) was ascertained to be almost invariably higher than that at the net mouth (v_0 m/sec); this tendency was noted to be especially remarkable when the cod end was kept opened. The value of v/v_0 obtained from the theoritical formula on the velocity ratio inside and outside the net, namely [the formula is omitted] was ascertained to be 1.21, in case of the theoritical value, and 1.11 in case of the experimental value: here the difference was noted to be almost zero, considering the possible errors in measurement. b) The relationship between the net resistance (R kg) and the towing speed (V m/sec) was ascertained to be: In case of the closed cod end: R=213V^{1.48}. In case of the opened cod end: R= 184V^{1.37}. By this was shown the fact that the variation of the net shape in the net shape in the former net was less than that in the latter one