硝子玉浮子の流水抵抗について-I : 各種硝子玉浮子及び球の抗力係数の比較

概要

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The glass floats used for the fishing net are coverd commonly shelter-mesh for respective fishing gears. Among them, the resistance of those used for the Japanese trawr, the ottei trawl and the trap nets were measured experimentally in company with that of floats without the shelter, and they were compared with that of the sphere. The results oobtained may be summerized as follows: 1) When the current speed (U) exceeds 0.2-0.4 m/sec, the water resistance of floats (R) varies proportionally with U2, while when the speed does not reach to the above, R is in poportion to U. 2) When the Reynolds number (Re) is in the range of 3×104-5×105, the drag coefficient (Cα) of the bare glass float is measured about 0.36 coinciding with that of the sphere, irrespetcive of its Re. While when the float is covered by mesh, the value of Cα are measured about 0.75, 0.90 and 0.75, i.e. 2, 2.5 and 2 times as large as that of the spere, for the Japanese trawl, the otter trawl and the trap net, respectivelly. 3) When the Re of floats having the same style of coves is equal, the diameter of float is the larger, the Cα is the smaller.
公益社団法人日本水産学会の論文