A study on the effects of turbulence scale on flutter of long span bridges

湍流尺度对大跨桥梁颤振的影响研究

基本信息

批准号：
01550367
负责人：
NAKAMURA Y.
金额：
$ 1.41万
依托单位：
Research Institute for Applied Mechanics, Kyushu University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1989
资助国家：
日本
起止时间：
1989 至 1991
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-01550367/
关键词：
Long Span Bridge Turbulence Scale Flutter Galloping Buffeting 大気乱流自然風の乱れ

项目摘要

Engineering structures such as long span bridges and tall buildings are exposed to highly turbulent wind. Since long span bridges are susceptible to flutter, e. g. galloping, torsional flutter, vortex excitation, etc., the effects of turbulence on flutter have been a longstanding problem. The ratio, L_x/h, of turbulence integral scale L_x to the body size h is one of the measures which identify the turbulence effect. In the present research, galloping of rectangular prisms is considered. The principal purpose is to comprehensively understand the effects of turbulence scale on galloping over a wide range of L_x/h. Not only 2-D rectangular prisms but also 3-D prisms with one end fixed to the wall (3-D model) were used in order to attain larger values of L_x/h. Turbulent flows were generated by different grids with intensity u'/U about 10%, where u'is the r. m. s. of the u-component of velocity fluctuation and U is the free stream velocity.2-D model : Galloping is investigated on rectangu … More lar prisms with d/h of 0.6-3.0, where d is the depth and h is the height of the prism. (a) d/h=0.6-1.0 : Galloping occurs for both the uniform and turbulent flows with a slightly positive betaa, the aerodynamic growth rate of oscillation, where the scale effect is not significant. The oscillation due to buffeting is very weak. (b) d/h=2.0 : Galloping vanishes for the turbulent flows because of the promotion of reattachment of the separated-shear-layer to a side face, whereas galloping occurs for the uniform flow. With increasing L_x/h, betaa for the turbulent flows asymptotes to that for the smooth flow. This clearly shows that galloping is dependent on turbulence scale. (c) d/h=3.0 : Galloping vanishes for both the uniform and turbulent flows so that betaa negative. With increasing L_x/h, betaa decreases and tends to that for the uniform flow.3-D model : Galloping is investigated on rectangular prisms with d/h of 2.0 and 3.0. With increasing L_x/h, betaa for turbulent flows asymptotes to that for the smooth flow in a similar way to the 2-D model.Buffeting : In addition to galloping, models with d/h=2.0 and 3.0 at high reduced flow velocities are suffered from buffeting in turbulent flows with large Lx/h. The amplitude of buffeting increases rapidly at L_x/h of 2.0-3.0, but beyond around 10.0, the amplitude approaches an upper hmit. Less

大跨度桥梁和高层建筑等工程结构面临着高湍流风的影响，由于大跨度桥梁容易受到颤振、扭转颤振、涡激等影响，因此湍流对颤振的影响一直是一个长期存在的问题。湍流积分尺度L_x与物体尺寸h的比值L_x/h是识别湍流效应的指标之一。考虑了矩形棱柱的舞动，主要目的是全面了解湍流尺度对大范围 L_x/h 舞动的影响，不仅是 2 维矩形棱柱，还包括一端固定在墙上的 3 维棱柱。（3-D 模型）是为了获得更大的 L_x/h 值而由不同的网格生成，强度 u'/U 约为 10%，其中u' 是速度波动的 u 分量的 r，U 是自由流速度。二维模型：在 d/h 为 0.6-3.0 的矩形棱镜上研究驰骋，其中 d 是深度， h 是棱镜的高度 (a) d/h=0.6-1.0：βa 稍为正值的均匀流和湍流都会发生舞动，振荡的气动增长率，其中由抖振引起的振荡非常弱 (b) d/h=2.0：由于促进了分离剪切的重新附着，湍流的舞动消失。 -层到侧面，而均匀流会发生舞动，随着 L_x/h 的增加，湍流流的 betaa 渐近线。这清楚地表明，舞动取决于湍流规模 (c) d/h=3.0：对于均匀流和湍流来说，舞动消失，因此随着 L_x/h 的增加，betaa 减小并趋向于该值。 3-D 模型：随着 L_x/h、betaa 的增加，在 d/h 为 2.0 和 3.0 的矩形棱柱上研究舞动。湍流渐近线与平滑流的渐近线与二维模型类似。缓冲：除了舞动之外，d/h=2.0 和 3.0 的模型在高降低流速下还会受到湍流中的抖振大 Lx/h 抖振幅度在 L_x/h 为 2.0-3.0 时迅速增加，但超过 10.0 左右，幅度接近上限。