杨佐美(1997-), 女, 硕士研究生, 主要从事流致振动研究, (E-mail)
针对双柱体这种极具代表性的多柱体结构,采用数值方法研究错列距离改变引起的双柱体流致振动特性的变化,分析间隙流与振动响应之间的相互影响关系。结果显示:错列双柱体的振动模态存在周期振动、双周期振动、多周期振动和拟周期振动等多种模态。上游柱体振幅受间距比的影响很小,间距比变化时,最大振动幅值均在约化速度
Aiming at two cylinders which is a very typical multi-cylinder structure, the influence of staggered distances on the flow-induced vibration response characteristics of two circular cylinders is studied using numerical simulation method. and the interaction relation between the gap flow and the vibration response of cylinders is obtained. The results illustrate that FIM mode of two cylinders include periodic vibration, double-cycle vibration, multiple-periodic vibration, and quasi-periodic vibration. With the change of staggered spacing, the amplitude of upstream cylinder is almost unaffected, and maximizes at
当流体流过弹性支撑的钝体[
除此之外,流致振动是一种将流动能转变为结构振动机械能的现象。近年来,就有学者提出了具有生态友好、经济效益高和低起动流速等优点的流致振动清洁能源收集系统[
综上所述,间距比是影响双柱体流致振动响应的关键性因素。而Griffith对错列双柱体的研究中提到了间隙流的概念,关于间隙流的生成没有多的阐述,间隙流的产生对于振动的影响机理还处于未知状态。因此,文中针对错列双柱体,研究了它在不同间距比下的幅频响应特性和尾流形态,讨论振动响应随间距比的变化,获悉间隙流对振动的影响。
柱体振动系统简化为质量阻尼弹簧(
柱体物理模型
Physical model of cylinders
柱体振动系统参数
Parameters of cylinders oscillatory system
系统参数 | 单位 | 柱体振子 |
柱体直径 |
m | 0.04 |
柱体长度 |
m | 0.5 |
弹簧刚度 |
N/m | 40.19 |
阻尼 |
N·s/m | 0.68 |
系统质量 |
kg | 1.38 |
流体密度 |
kg/m3 | 999.10 |
流体运动粘度 |
m2/s | 1.14×10-6 |
运用有限体积法,基于Spalart-Allmaras湍流模型,求解非定常雷诺平均Navier-Stokes方程组。控制方程为
式中,
柱体运动方程[
式中,
式中,Δ
如
计算区域及边界条件
The computational domain and its boundary condition
采用结构化网格进行网格划分,对近壁面区域实行网格加密处理,并将拓扑网格与耦合界面相结合,从而减小多柱体大幅振动时网格扭曲变形引起的计算误差。拓扑网格是一种底层静态的网格,该网格本身并不随运动子块运动,不会因拉伸或挤压产生网格形变,其特点在于子块区外围网格会随子块运动而自动生成或崩塌消失[
PTC双柱体网格无关性验证
Grid-independent study for two PTC cylinders(
序号 | 网格尺寸 | 阻力系数 |
升力系数 |
|||
上游 | 下游 | 上游 | 下游 | |||
1 | 180×60 | 1.029 | -0.060 | 0.287 | 0.537 | |
2 | 240×70 | 1.039 | -0.065 | 0.299 | 0.561 | |
3 | 360×80 | 1.038 | -0.067 | 0.298 | 0.559 |
中等密度近壁面网格
Medium grid the close-up grid
分析PTC双柱体流致振动的时域曲线和频域曲线,发现随着错列间距比和约化速度的改变,柱体振动特性发生变化。
圆柱振动的时域曲线和频域曲线(
Time domain curve and frequency domain curve of the vibration cylinder at
当错列间距比增长时,双柱体振动特性也会发生改变,如
圆柱振动的时域曲线和频域曲线(
Time domain curve and frequency domain curve of the vibration cylinder at
结合
振幅和频率是反映振子运动特性和流致振动响应的关键参数,柱体流致振动分支的转变伴随着幅频响应特性的改变。文中采用的振幅是均方根振幅,振动频率是通过快速傅里叶变换取得。不同间距比下双柱体的振幅频率响应如
错列双圆柱的振幅响应
The amplitude response of two circular cylinders
错列双圆柱的频率响应
The frequency response of two circular cylinders
如
如
柱体在流域中所受流体力的大小决定了柱体的振动幅度和振动频率,而流体力的变化又与柱体的漩涡脱落息息相关。因此,分析柱体流致振动的尾涡结构显得尤为重要。随着约化速度的变化,柱体振动经历不同的分支,尾涡结构也随着发生变化,常见的典型尾涡结构包括:S、P和P+S等。本节对4个典型工况的计算结果进行了讨论。流致振动是一种周期性运动,尾涡形态也出现周期性变化,文中在分析柱体尾涡结构时,选取了能够清晰观察到尾涡形态的特定时间点的计算结果。值得注意的是,由于文中数值计算基于雷诺平均理论,所以流场湍流信息得到的是平均信息。
如
Wake pattern of cylinders when
Wake pattern of cylinders when
Wake pattern of cylinders when
Wake pattern of cylinders when
针对错列双柱体,采用模拟方法研究了不同间距比下柱体的流致振动特性,在计算工况内得出的主要结论如下:
1) 错列双柱体的振动模态包括:周期振动、双周期振动、多周期振动和拟周期振动。
2) 错列间距比改变时,上游柱体的振幅变化较小,最大值均在
3) 错列双柱体的2个柱体振动频率以相同的规律随约化速度变化。不同间距比下,上游柱体均出现不同程度的频率锁定现象,对应获得柱体最大振幅。2个柱体的振动频率比的差值随约化速度的增大逐渐缩小。
4) 当约化速度相同时,随着间距比增大,上游柱体漩涡脱落在2个柱体之间形成间隙流。当
5) 当错列间距相同时,错列双柱体的尾迹形态受约化速度的影响较大。在约化速度比较大时,会出现复杂的漩涡再附着现象,流体与结构之间的耦合作用加强,漩涡脱落模态多样化,错列双柱体的振动幅度因此得到强化。
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