EXPERIMENTAL DATA OF WAKE-INDUCED VIBRATION ANALYSIS FOR TANDEM CYLINDERS WITH SPACING RATIO OF 2.5 TO 10

Data result from measurements with a condenser microphone, hot wire anemometry, and accelerometer in an aerodynamic channel to study the influence of the space ratio on the flow-induced vibration of a cylinder in a tandem arrangement. The upstream cylinder is rigidly fixed to the channel, while the cylinder placed downstream is free to vibrate transversally to the flow.
The Reynolds number for the tested cases ranged between 1.12x104 to 2.29x104, based on the diameter of one cylinder, the reference velocity measured with a Pitot Tube, and the kinematic viscosity at the environmental conditions of the laboratory.
25 mm smooth cylinders with 25mm diameter made of commercial PVC tubes were used. L/D ratios tested were 2.5, 5, 8, and 10. Measurements of a single cylinder were also performed as a base case. The cylinder free-to-vibrate is attached to two blades allowing to adjust the stiffness [1].
Flow visualizations using fixed cylinders were performed in a water channel. Test section and geometry had same dimensions as the aerodynamic channel [2]; the Reynolds number was Re = 2 x 103. Dye was injected through the cylinder’s wall by gravity from two ink tanks. Video resolution was 1920 x 1080 pixels at 30 FPS.
The pressure fluctuations were measured in the region between the two cylinders with a Brüel & Kjaer Cartridge type 4138 1/8” diameter condenser microphone placed at the channel upper wall, connected to an amplifier Brüel & Kjaer type 2633.
Cylinder acceleration was measured with an ADXL335 analogic accelerometer, attached to the extremity of the cylinder.
For the measurements of the flow velocity and velocity fluctuations, a DANTEC StreamLine constant temperature hot-wire anemometry system with a 55P11 single-wire probe placed on the wake of the second cylinder was used.
Data acquisition employed an NI USB-9162 16 bits A/D board with a sampling frequency of 1 kHz and a low pass filter set at 0.3 kHz.
The mass-damping parameters were equal for the single cylinder and for the arrangements with space ratio L/D = 2.5 to L/D = 8. The mass ratio was m*=539, the damping ratio ξ = 0.0169, and the natural frequency fn= 5.86 Hz. All parameters were obtained from the free vibration signal of the experimental setup.
For the case of L/D = 10, the setup characteristics changed due to the increase in the length of the longitudinal gap. Data for L/D = 2.5 to L/D = 10 had a natural frequency fn= 3.906 Hz and the damping ratio was ξ = 0.011.

References
[1] Neumeister, R. F., Petry, A. P., & Möller, S. V. (2021). Journal of Pressure Vessel Technology, 143(3).
[2] Habowski, P. B., de Paula, A. V., & Möller, S. V. (2020). Journal of the Brazilian Society of Mechanical Sciences and Engineering, 42, 1-21.