Abstract
The two-dimensional Karman vortex street behind a circular cylinder is known to become unstable and have three-dimensionality up to Re=200. In this paper, the global numerical stability analysis was performed for the flow and the stability characteristics were investigated in the range from Re=170 to 200. The analysis clearly showed the existence of the transition point. The computed critical Reynolds number was 190 and the critical spanwise wavenumber was 1.61. The stability spectra and the spatial form of the three-dimensional eigenvectors are presented. To study further, the energy budget was computed by making use of the data of eigenvectors. It was found that the increment of the production term is substantial within the investigated range of parameters and is considered the main cause of instability beyond the critical point.
