報告書番号

U01049

タイトル（和文）

直交流中の十字管単管周りの流れおよび流体力の特性

タイトル（英文）

Characteristics of flow around a cross-shaped tube and its fluid force

概要 （図表や脚注は「報告書全文」に掲載しております）

直交流中の十字管単管周りの流れとその流体力の特性を明らかにするため，流れの可視化実験および流体力の測定を行うとともに，十字管単管に生じる可能性がある流力振動について検討した．その結果，以下のことがわかった．①十字管周りの流れは，流れの入射角が15°付近を境として，流れの入射角が小さい条件では完全剥離型流れ，流れの入射角が大きい条件では再付着流れとなる．②十字管の定常抗力係数は0.9～1.5程度，ストローハル数は1.5～2.1程度であり，定常揚力係数は常に負である．③上述のフローパターンの変化に応じて，流れの入射角が15°付近で，定常抗力係数は最小に，定常揚力係数は絶対値が最大に，ストローハル数は最大となる．④これらの特性は，正方形柱のそれとほぼ合致する．⑤流れの入射角が0°付近では，渦励振とギャロッピングが生じる可能性があり，流れの入射角が45°付近ではILEV振動が生じる可能性がある．

概要 （英文）

Flow visualization around a cross-shaped tube and measurements of its fluid forces were conducted in a water tunnel to investigate their characteristics. Possibility of flow-induced vibrations was also discussed on the basis of those experimental results. Finally, the following results were obtained.①Flow around a cross-shaped tube is classified into two patterns. One is Non-reattachment flow, and the other is Reattachment flow. Non-reattachment flow is observed in case of small flow angle of attack, and reattachment flow is observed in case of large flow angle of attack. The critical angle of attack where the flow pattern changes from the former to the latter is about 7.5 to 15 degree.②The steady drag coefficient of cross-shaped tube is in the range of 0.9 to 1.5, and the Strouhal number is about 0.15 to 0.21. The steady lift coefficient is negative in any angle of attack.③At the critical angle of attack, the steady drag coefficient has its minimum value, while the Strouhal number and the absolute value of the steady lift coefficient attain to their maximum, corresponding to the change of the flow pattern described above.④The characteristics of flow around a cross-shaped tube and its fluid forces are similar to those of square prism.⑤Vortex induced vibration and galloping are possibly caused by the flow in the case that the angle of attack is around 0 degree, while ILEV(Impinging leading-edge vortices) resonance can occur on condition that the angle of attack is around 45 degree.

報告者

キーワード