蛙又結節網地の抗力係数におよぼすレイノルズ数の影響

概要

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This study deals with the fluid dynamical drag coefficient of a plane netting concerning the Reynolds number based on the diameter of a netting twine. Six kinds of Weaver's-knot netting were used for this experiment; the range of the ratio of twine diameter and leg-length (d/l) were from 0.037 to 0.124. The nettings were fixed on a circular shaped frame hung 29.3% of hang-in ratio, and set into a flume tank normal to the flow direction.The drag was measured by a three component load-cell as a X-component and recorded on a chart-recorder. In this case the drag coefficients were calculated by Newton's law of resis-tance, based on projective area of netting twine.The current flow was set at 5, 10, 25, 50, 75, 100 and 125cm/s monitored by a super-sonic current meter, and the range of Reynolds number were from 1.7×10 to 1.8×103.The results obtained were as follows:1) A Reynolds number of 2×102 was determined to be the critical value for transition of drag coefficient.2) For Reynolds number greater than 2×102 the drag coefficient was determined to be 1.14.3) For Reynolds number less than 2×102 the drag coefficient followed the empirical equation: CD(90)=14.81(Re)-0.49.
日本水産學會の論文