| Autor: |
Ryabinin, A. N., Veligzhanin, A. A. |
| Zdroj: |
Vestnik St. Petersburg University: Mathematics; Dec2022, Vol. 55 Issue 4, p489-496, 8p |
| Abstrakt: |
The work considers the rotational and translational oscillations of three cylinders differing in terms of the ratio of the length to the cylinder diameter (aspect ratio). The cylinders are suspended in the test section of a low velocity wind tunnel on a wire suspension equipped with steel springs. In the equilibrium position, the axis of the cylinders is directed horizontally and parallel to the freestream velocity vector. Under the influence of the air flow, the cylinders can execute rotational or translational oscillations. The two suspension springs are equipped with semiconductor strain gauges that measure the periodically changing tension of the springs during oscillations. The analog signal from the strain gauges is transmitted to a PC oscilloscope, which transmitted it in digital form to a computer. After calibration of the device and decoding of the signal, the frequencies and amplitudes of translational oscillations in the vertical direction and rotational oscillations around the horizontal axis passing through the center of the cylinder and perpendicular to the freestream velocity vector are determined. It turns out that in the studied range of cylinder elongations there is a transition from rotational to translational oscillations. A cylinder with an aspect ratio of 1.9 performs steady rotational oscillations under the influence of wind, and their amplitude increases with increasing air-flow velocity. The previously proposed mathematical model correctly predicts rotational oscillations. The square of the amplitude of rotational oscillations is a linear function of the Strouhal number if the velocity of the air flow is sufficiently large. Translational oscillations of the cylinder with an aspect ratio of 1.9 are damped. A decrease in the aspect ratio of the cylinder down to 1.5 is accompanied by a decrease in the amplitudes of rotational vibrations. At low air-flow velocities, translational oscillations with a small amplitude are registered. Further reducing the aspect ratio to 1.0 eliminates rotational oscillations entirely. The amplitude of translational oscillations increases. Translational oscillations occur in a limited range of air-flow velocities. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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