流線形枠による流れに平行な網地の抵抗の測定

概要

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By using a specially designed streamline frame, the drag of netting parallel to a water flow was measured at a range of values of mesh angle ∅, i.e. the half angle between two adjacent bars. The friction drag coefficient Cf of netting parallel to a flow based on the area of netting varies considerably with the ratio of twine diameter D to bar length L, i.e. D/L, and the mesh angle, while it decreases very slightly with increasce the Reynold's number based on the length of netting. At constant mesh angle, Cf increased linearly with the ratio D/L. The drag coefficient Cf was found to be constant over a range of either D or L, when both the ratio D/L and the mesh angle ∅ were kept constant. Varying the mesh angle ∅ for the same netting, Cf decreased slightly with increasing ∅ up to angles between 20° and 30°, but above 30°Cf increased considerably with ∅. From these experimental results, excepting angles below 20°, the following formula for friction drag coefficient Cf was derived Cf=0.11 √(D/L) tan ∅.