Mechanism of ovalling vibrations of cylindrical shells in cross flow

The mechanism of wind-induced ovalling vibrations of cylindrical shells is numerically investigated by using a vortex method. The subject of this pape r is limited to a two-dimensional structure in the subcritical regime. The aerodynamic stability of the ovalling vibrations in the second to fourth ci rcumferential modes is discussed, based on the results of a forced-vibratio n test. In the analysis, two modal configurations are considered; one is sy mmetric and the other is anti-symmetric with respect to a diameter parallel to the flow direction. The unsteady pressures acting on a vibrating cylind er are simulated and the work done by them for one cycle of a harmonic moti on is computed. The effects of a splitter plate on the flow around the cyli nder as well as on the aerodynamic stability of the ovalling vibrations are also discussed. The consideration on the mechanism of ovalling vibrations is verified by the results of a free-vibration test.