INTERFERENCE EFFECT OF GROUPED STRUCTURES EXPOSED TO THE WIND ACTION

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angličtina

This paper deals with a numerical investigation of the full dynamic response of staggered circular cylinders. The system has a low damping ratio and flexible spring suspenders support both cylinders. The system is analyzed in 7 cases, changing the along-wind distance of the cylinders for 6D up to 24D by 3D. Across-wind distance of centers of the cylinders is 3D, where D is the diameter of cylinders. Calculated Reynolds number is 1000, thus the flow is laminar, belonging into the subcritical region. Two dominant frequencies are apparent from the across-wind forces. It is the natural frequency and the vortex shedding frequency. The distance 6D in the closest case is enough to prevent the cylinders from the shielding effect, that may occur for X/D < 3, so that the along-wind response is similar in all computed cases. Comparing across-wind deflections we may deduce that the across-wind forces of the second cylinder are predominantly produced by the vortex shedding of the first cylinder. The behavior of the centers in the case with X/D = 6 is excited mostly by the vortex shedding, in contract to the case X/D = 24 where the loading forces (pressures) act in a more stochastic manner. In such a case we are not able to describe the deflection orbit of the cylinder as an elliptical one. Also structural parameters exert strong control over the characteristics of the wake galloping. In particular, the values of the spring constants require attention. In addition, the effect of other parameters such as Reynolds number, surface roughness, unequal diameter of cylinders, etc. are important topic for the future research of the fluid-solid interaction problems.

interference, wind, group, galloping

NEVAŘIL, A., KALA, J.

2004

28. 7. 2004

Jyväskylä, Finland

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