EXPERIMENTAL DATA OF OSCILLATORY BEHAVIOR ANALYSIS OF TWO PENDULUM-LIKE TANDEM CIRCULAR SLENDER CYLINDERS

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].