Experimental data of the space ratio influence on the excitation frequencies of one and two cylinder free to vibrate in tandem arrangement

Data result from careful measurements with accelerometers in an aerodynamic channel to study the influence of the space ratio on the flow-induced vibration of two cylinders in tandem arrangement with one or both cylinders free to vibrate. The aerodynamic channel is rectangular (0.193 X 0.146 m), with acrylic walls. A centrifugal blower of 0.75 kW impels the air through a diffuser, two honeycombs, and two screens. The turbulence intensity is 1% of the reference velocity, measured with a Pitot tube upstream of the test section. The Reynolds number ranged from 7100 to 24000, based on one cylinder diameter, and the reference velocity. The cylinders are smooth with 25mm diameter and L/D-ratios of 1.26, 1.4, 1.6, and 3.52. The cylinders free-to-vibrate in the transversal direction, are attached to two blades allowing the variation of length, to change the stiffness, as in Neumeister et al. (2021). The blockage ratio is 13.01 %. Nomenclature SC indicates a single cylinder (as reference). For tandem cylinders, FL means that the first cylinder is free to vibrate, for SL, the second cylinder, and BV both cylinders are free to vibrate. The cylinder acceleration is measured with accelerometers ADXL 335, data acquisition frequency, 1 kHz, low pass filter at 0.3 kHz. A 16bits A/D board NI USB-9162 was employed for the data acquisition. The mass-damping parameters were equal for the Cases 01 to 09: the mass ratio m*=608, the damping ratio ζ = 0.03, and the natural frequencies, fn1 = 7.8Hz and fn2 = 21.5 Hz. Cases 10 and 11 considered acceleration and flow velocity for m* = 539, ζ = 0.004 and the natural frequencies, fn1 = 8.8Hz and fn2 = 23.4 Hz. The cases with both cylinders had three configurations. First BV-configuration, Case 12: the first cylinder with a lower natural frequency than the second one. The parameters for the first cylinder were m* = 502, the damping ratio ζ = 0.003 and the natural frequencies are fn1 = 13.7Hz and fn2 = 36.2 Hz. For the second cylinder, m* = 547, ζ = 0.006 and the natural frequencies are fn1 = 24.4 Hz and fn2 = 71 Hz. Second BV-configuration, Case 13: the first cylinder with a higher natural frequency than the second. The parameters for the first cylinder were m* = 502, ζ = 0.002 and the natural frequencies are fn1 = 29.3 Hz and fn2 = 58.6 Hz. For the second cylinder, m* = 547, ζ = 0.009, and are fn1 = 10.7 Hz and fn2 = 30.3 Hz. Third BV-configuration, Case 14: both cylinders with the natural frequency in the same range. The parameters for the first cylinder were m* = 502, ζ = 0.008 and the natural frequencies fn1 = 10.8 Hz and fn2 = 22.5 Hz. For the second cylinder, m* = 547, ζ = 0.007 and the natural frequencies are fn1 = 10.7 Hz and fn2 = 31.2 Hz. Reference Neumeister, R. F., Petry, A. P., and Möller, S. V. 2021a). Experimental Flow-Induced Vibration Analysis of the Crossflow Past a Single Cylinder and Pairs of Cylinders in Tandem and Side-by-Side. Journal of Pressure Vessel Technology, v. 143(3), p. 031402.本数据集源于在气动试验通道内使用加速度计开展的精准测量实验，旨在研究间隙比对串列布置的两根圆柱的流致振动的影响，实验中一根或两根圆柱可自由振动。 该气动试验通道为矩形截面（0.193 × 0.146 m），壁面采用亚克力（acrylic）材料制作。功率为0.75 kW的离心鼓风机驱动气流依次经过扩压器、两个蜂窝器及两道筛网流过通道。试验段上游采用皮托管（Pitot tube）测得湍流强度为参考风速的1%。 基于单圆柱直径与参考风速计算得到的雷诺数范围为7100至24000。 实验所用圆柱为光滑圆柱，直径25 mm，长径比（L/D-ratio）分别为1.26、1.4、1.6及3.52。圆柱可沿横向自由振动，通过连接两个叶片调整长度以改变刚度，实验设置参考Neumeister等人（2021）的研究方案。阻塞比（blockage ratio）为13.01%。 命名规则如下：SC（single cylinder，单圆柱）作为对照基准；对于串列圆柱布置，FL表示上游圆柱可自由振动，SL表示下游圆柱可自由振动，BV表示两根圆柱均可自由振动。 圆柱加速度由ADXL 335型加速度计采集，数据采集频率为1 kHz，低通滤波器截止频率设为0.3 kHz。实验采用16位A/D采集板NI USB-9162完成数据采集。 案例01至09的质量阻尼参数一致：质量比m*=608，阻尼比ζ=0.03，固有频率分别为fn1=7.8 Hz与fn2=21.5 Hz。 案例10与11的质量比m*=539，阻尼比ζ=0.004，固有频率分别为fn1=8.8 Hz与fn2=23.4 Hz，实验同时采集加速度与流速数据。 采用两根圆柱的实验包含三种BV配置： 第一种为BV配置（案例12）：上游圆柱固有频率低于下游圆柱。上游圆柱参数为：质量比m*=502，阻尼比ζ=0.003，固有频率fn1=13.7 Hz、fn2=36.2 Hz；下游圆柱参数为：质量比m*=547，阻尼比ζ=0.006，固有频率fn1=24.4 Hz、fn2=71 Hz。 第二种为BV配置（案例13）：上游圆柱固有频率高于下游圆柱。上游圆柱参数为：质量比m*=502，阻尼比ζ=0.002，固有频率fn1=29.3 Hz、fn2=58.6 Hz；下游圆柱参数为：质量比m*=547，阻尼比ζ=0.009，固有频率fn1=10.7 Hz、fn2=30.3 Hz。 第三种为BV配置（案例14）：两根圆柱固有频率处于同一区间。上游圆柱参数为：质量比m*=502，阻尼比ζ=0.008，固有频率fn1=10.8 Hz、fn2=22.5 Hz；下游圆柱参数为：质量比m*=547，阻尼比ζ=0.007，固有频率fn1=10.7 Hz、fn2=31.2 Hz。 参考文献 Neumeister, R. F., Petry, A. P., 及 Möller, S. V. 2021a. 单圆柱及串列、并列双圆柱横流流致振动的实验分析. Journal of Pressure Vessel Technology（压力容器技术）, 第143卷第3期, 文章编号031402。