| 作成者 |
|
|
|
| 本文言語 |
|
| 出版者 |
|
|
|
| 発行日 |
|
| 収録物名 |
|
| 巻 |
|
| 号 |
|
| 開始ページ |
|
| 終了ページ |
|
| 出版タイプ |
|
| アクセス権 |
|
| Crossref DOI |
|
| 概要 |
Breakdown and rearrangement of a primary vortex street shed from a circular cylinder in the far wake are experimentally examined for 70 < R < 154 (R is the Reynolds number based on the diameter of the... cylinder). According to the vorticity fields obtained using digital image processing for visualized flow fields, the primary vortex street breaks down into a nearly parallel shear flow of Gaussian profile at a certain downstream distance, before a secondary vortex street of larger scale appears further downstream. The process leading to the nearly parallel flow can be explanined as the evolution of the vortex regions of an inviscid fluid if we invoke the observation that the distance between the two rows in the primary vortex street increases with the downstream distance. Numerical computations with the discrete vortex method also support this explanation. Next, the wavelengths, a_1 and a_2, of the primary and secondary vortex streets are calculated from the above vorticity fields, and are also measured from the flow patterns obtained using the aluminium dust method. The ratio a_2/a_1 decreases with increasing R, and ranges from 1.7 to 2.6. Moreover, the wavelength a_2 is a little smaller than that of the most unstable mode in the linear stability theory applied to the above nearly parallel flow. The speeds of the vortex streets relative to the fluid at infinity are also measured, and are 0.12U-0.19U and 0.03U-0.10U for the primary and secondary ones, respectively. Here U is the speed of the cylinder.続きを見る
|
Mendeley出力
039110_p001