Bistable flow data from the wake behind two parallel cylinders with P/D = 1.26 and various Reynolds numbers

Data result from careful measurements with hot wires in an aerodynamic channel to study the phenomenon of the bistability in the wake of two parallel cylinders submitted to a turbulent cross flow. The cylinders were made from commercial PVC (PolyVinyl Chloride) with 25.1 mm diameter and pitch-to-diameter ratio p/d = 1.26.
The experimental time series were acquired in one of the aerodynamic channels of the Fluid Mechanics Laboratory of UFRGS. The channel is made of acrylic glass, with a rectangular test section of 0.146 m height, width of 0.193 m, and 0.9 m length. The airflow is driven by a centrifugal fan with 0.75 kW and passes through two honeycombs and two screens to reduce the turbulence intensity to about 1% of the free stream velocity in the test section. Upstream the test section, placed in one of the sidewalls, a Pitot tube measures the reference velocity of the impinging flow. This velocity is approximately the average velocity in the channel used for the determination of the Reynolds number. The Reynolds numbers (Re) of the experiments were 7220, 11417, 14434, 15494, 19442, and 23258, based on the cylinder diameter and the air properties at room temperature.
The axial component of the wake flow velocity behind the cylinder set and its fluctuations was measured with a DANTEC StreamLine constant hot-wire anemometer equipped with a DANTEC 55P11 single wire probe. The sampling frequency was 1 kHz, with a low pass filter at 300 Hz, and the time acquisition was 65,536 s. Data acquisition was performed by a USB 16-bit NI USB-9162 A/D board.

Instantaneous velocity values for each Reynolds number: time (s), wake flow velocity (m/s).
Re_7720.txt
Re_11417.txt
Re_14434.txt
Re_15494.txt
Re_19442.txt
Re_23258.txt

本数据集源自气动风洞中利用热丝探针开展的精准测量实验，旨在研究湍流横流作用下两平行圆柱尾流的双稳态现象。实验所用圆柱采用商用聚氯乙烯（PolyVinyl Chloride, PVC）加工而成，直径为25.1 mm，节径比p/d=1.26。

实验时间序列数据采集于UFRGS流体力学实验室的一座气动风洞。该风洞试验段由有机玻璃制成，尺寸为高0.146 m、宽0.193 m、长0.9 m。气流由功率0.75 kW的离心风扇驱动，先后经过两个整流蜂窝器与两个整流筛网，将试验段来流的湍流强度降至约为来流速度的1%。在试验段上游的侧壁处安装有皮托管（Pitot tube），用于测量入射流的参考流速，该流速近似为风洞通道内的平均流速，用于雷诺数的计算。本实验的雷诺数（Re）基于圆柱直径与室温下的空气物性参数计算得到，取值分别为7220、11417、14434、15494、19442及23258。

实验采用配备DANTEC 55P11型单丝探针的DANTEC StreamLine型恒温热线风速仪（constant hot-wire anemometer），测量了圆柱组后方尾流流速的轴向分量及其脉动分量。采样频率设置为1 kHz，搭配300 Hz的低通滤波器，单次采集时长为65536 s。数据采集通过USB接口16位NI USB-9162型模数转换板完成。

各雷诺数工况对应的瞬时速度数据保存为独立文本文件，文件包含两列数据：时间（单位：s）、尾流流速（单位：m/s），对应文件分别为Re_7720.txt、Re_11417.txt、Re_14434.txt、Re_15494.txt、Re_19442.txt、Re_23258.txt。