| 利用顶部柔膜颤振抑制三维方形棱柱气动力 |
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| 作者姓名： | 赵崇宇 王汉封 |
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| 作者单位： | 1.中南大学土木工程学院, 湖南长沙 410075 |
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| 基金项目： | 国家自然科学基金11472312 |
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| 摘 要： | 通过风洞实验研究了高宽比H/d=5的正方形棱柱顶部柔性薄膜颤振对柱体气动力特性的影响规律.模型宽度为40 mm，来流风速4~20 m/s，对应Reynolds数为10 960~54 800.柔性薄膜为厚度0.04 mm的高压聚乙烯膜，长度l=0.5~4 cm不等.实验发现，柔性薄膜的振动状态对三维方柱气动力特性有显著影响.低风速下，柔性薄膜不发生颤振，其对方柱气动力影响不大；随风速的增加，柔性薄膜发生颤振，方柱的时均阻力、脉动阻力和脉动侧向力最多分别减少约5%，25%和60%.柔膜发生颤振的临界风速随其长度增大而减小.只要柔膜发生颤振，其对柱体气动力的影响都是类似的，与其长度无关.流动可视化实验发现，薄膜的颤振改变了方柱绕流场，使柱体上半部分的反对称展向漩涡变为受膜拍动控制的对称结构，且越靠近自由端，此现象越明显.
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| 关 键 词： | 柔性薄膜 颤振 方形棱柱 气动力 流动控制 |
| 收稿时间： | 2020-05-25 |
Suppression of the Aerodynamic Forces on the Finite Square Cylinder Using a Flexible Film at its Free End |
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| Affiliation: | 1.School of Civil Engineering, Central South University, Changsha 410075, China2.National Engineering Laboratory for High-Speed Railway Construction, Changsha 410075, China |
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| Abstract: | The effects of a flexible film at the free end of a finite square cylinder on its aerodynamic forces were experimentally investigated. The width of the cylinder d was 40 mm and the aspect ratio H/d was 5. The oncoming flow velocity ranged from 4 to 20 m/s, corresponding to a Reynolds number of about 10 960 to 54 800. A flexible polyethylene film with the thickness of 0.04 mm was vertically attached at the leading edge of the cylinder free end. The length of film ranged from 0.5 to 4 cm. It is found that, the behavior of the flexible film has significant effects on the aerodynamic forces of the finite square cylinder. At a low wind speed, the film is statically deformed, which has negligible influences on the aerodynamic forces of the cylinder. The flexible film flaps at a high wind speed, resulting in a significant reduction in the aerodynamic forces on the cylinder. The maximum reduction in the mean drag, fluctuating drag and fluctuating lift reaches about 5%, 25% and 60%, respectively. The reduction in aerodynamic forces is similar for all tested films once the flapping occurs, although the critical velocity is different for the film with different lengths. Flow visualization indicates that, the flapping film induces strong vortices in the free-end shear flow, changing the alternate spanwise vortex into symmetrical, especially near the free end. |
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