EXPERIMENTAL DATA OF OSCILLATORY BEHAVIOR ANALYSIS OF TWO PENDULUM-LIKE TANDEM CIRCULAR SLENDER CYLINDERS
Description
Data from two experiments using a high-speed camera (HSC) and a PIV system in a streamlined channel were obtained to investigate the oscillatory behavior of two tandem cylinders mounted in a pendulum-like manner, as well as the flow characteristics around fixed cylinders. The recorded data include the lateral displacement of the cylinder (y^') and the PIV measurement results. The Reynolds number for these experiments varied between 16,000 and 24,000. This range was calculated based on the free flow velocity, the kinematic viscosity of air at ambient conditions, and the cylinder diameter (D) of 12.7 mm. The aerodynamic channel had a rectangular cross-section measuring 254 mm in height and 127 mm in width. It was primarily constructed using wooden panels, with the test section composed by aluminum and acrylic glass windows. The PIV system comprised a CCD camera with a resolution of 2752×2200 pixels, capable of storing 1,200 double frames per experiment. A 532 nm Nd:YAG laser was employed to illuminate the flow. This laser emitted two pulsed beams at a maximum frequency of 15 Hz. The camera and laser operation were synchronized by the acquisition system. DiEthyl-Hexyl-Sebacat (DEHS) particles with a maximum size of 1 µm were introduced to seed the flow for the PIV measurements. Two experiments using distinct setups were conducted, and their configurations are described below. Firstly, the lateral displacement of the cylinder was measured using an HSC positioned beneath the test section, recording at a resolution of 1920 × 1080 pixels and a frame rate of 120 Hz. In this configuration, the cylinders were vertically aligned and free to oscillate transversely to the flow, mimicking pendulum motion. The cylinders, made of aluminum with a diameter of 10 mm, were mounted on 3D-printed supports. Each support contained a pair of bearings and was attached to a threaded bar rigidly fixed at the top of the channel. Four spacing ratios (SR) were tested: 2.0, 3.5, 5.0, and 7.5, defined as the ratio between the center-to-center distance of the cylinders and their diameter (D). Additionally, for a spacing ratio of 4.5, the PIV methodology was applied under this setup. The Reynolds number varied from 16,000 to 24,000 and is specified in the corresponding files, alongside the spacing ratio. The mass ratio (m^*), representing the ratio of the cylinder's mass to the displaced fluid's mass, and the damping ratio (ζ) were key parameters for analyzing the results. The values were m*=810 and ζ=0.017. In the second setup, the cylinders were rigidly assembled in a horizontal orientation. In this case, the cylinders were constructed from acrylic glass with a diameter of 12.7 mm. Three spacing ratios were tested: 2.0, 3.5, and 5.0, at a Reynolds number of 21,000. Further details regarding the setups, wind tunnel, experiments, and methodology are available in the work by Habowski et al. [1].
Files
Steps to reproduce
The results of the lateral displacement of the cylinders are saved in files named using the prefix "disps_". The file nomenclature further incorporates the spacing ratio (SR) and the Reynolds number (Re), with both identifiers separated by an underscore "_" and followed by their respective values. The data are provided in .csv format, where each file includes the lateral displacement of the downstream cylinder, the in-line displacement of the downstream cylinder, the lateral displacement of the upstream cylinder, and the in-line displacement of the upstream cylinder. All measurements are given in millimeters [mm], relative to the cylinders' rest position. The rows represent time, with a fixed time step of 1/120 seconds [s]. The PIV results were pre-processed using DaVis software to generate .dat files from the recorded videos. The data is organized into folders, where each folder corresponds to a tested SR at a fixed Reynolds number of 21,000. Each folder contains 1,200 files, with each file representing an individual time step captured by the PIV system, with a time interval of 1/15 seconds [s]. The columns in these files include: axial ("x-") and transversal ("y-") positions, measured in millimeters [mm]; axial ("u-") and transversal ("v-") velocities, measured in meters per second [m/s]; and a validity flag, where a value of 1 indicates a valid frame and 0 denotes a frame to be disregarded. The files in each folder are named using the format "B1200.dat," where the numerical value corresponds to the frame number. Therefore, images can be obtained by plotting the results from each file, from B0001 to B1200.