The separation of flow past a circular cylinder on aβ-plane |
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Authors: | Tomonori Matsuura |
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Institution: | (1) Faculty of Engineering, Ibaraki University, Nakanarusawa-machi 4-12-1, 316 Hitachi, Japan |
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Abstract: | Effects of the Ekman friction on the prograde (eastward) flows past a cylinder on a -plane are investigated when
(= R
2/U, whereR is the cylinder radius andU the freestream speed) O(1) and (=2E
k
1/2/R
0·![delta](/content/t282qq851657t564/xxlarge948.gif) O(1) where
is the non-dimensional beta parameter and the ratio of the square root of the Ekman numberE
k
multiplied by 2 to the Rossby numberRo multiplied by the aspect ratio (=H/R, whereH is the fluid depth). Previous studies without the Ekman friction have shown that the -effect inhibits flow separation for pragrade flows through the asymptotic boundary condition by shifting the region of the adverse pressure gradient toward the rear stagnation point. It is found that the Ekman friction alleviates this -effect on the exterior flow. In the Ek
1/4-boundary layer, on the other hand, Ekman friction suppresses the vorticity advection along the wall, which tends to make the boundary layer thickness thin and delay the flow separation. The Ekman friction thus affects flow separation in a complicated manner. Details of the boundary layer structures and the separation angles are described for 0.3<
<4.0 and 0.1< <1.5. |
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Keywords: | |
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