Hydrodynamic instability of separated viscous flow around a circular cylinder

A uniform viscous flow around a circular cylinder is studied numerically in the Reynolds number range from $0$ to $500$. It is shown that the existence and the basic properties of self-oscillatory regimes are specified by the evolution of their hydrodynamic instability. It is found that the vortex formation in the near wake is connected with the dynamics of the separation zone in the main flow. The values of critical Reynolds numbers for the four successive bifurcations of the self-oscillatory flow regimes are obtained. An interpretation of experimental data on the vortices in the near wake is discussed.