Mechanism of ovalling vibrations of cylindrical shells in cross flow

The mechanism of wind-induced ovalling vibrations of cylindrical shells is numericallyrninvestigated by using a vortex method. The subject of this paper is limited to a two-dimensional structurernin the subcritical regime. The aerodynamic stability of the ovalling vibrations in the second to fourthrncircumferential modes is discussed, based on the results of a forced-vibration test. In the analysis, two modalrnconfigurations are considered; one is symmetric and the other is anti-symmetric with respect to a diameterrnparallel to the flow direction. The unsteady pressures acting on a vibrating cylinder are simulated and thernwork done by them for one cycle of a harmonic motion is computed. The effects of a splitter plate on thernflow around the cylinder as well as on the aerodynamic stability of the ovalling vibrations are also discussed.rnThe consideration on the mechanism of ovalling vibrations is verified by the results of a free-vibration test.