The eigenanalysis of the steady flow proved to be very precise tool for evaluation of the critical Reynolds number and physical phenomena related with onset of instability in the bluff bodies wake flow. It enhanced the use of this approach to analyse different methods of the flow control. With the global non-parallel flow stability analysis it is possible to study the group of control problems classified as the "control via steady or quasi-steady modification of the boundary conditions". The method was tested for the flow around circular cylinder. The extensive experimental investigations of control cylinder in the wake region by Strykowski served as the reference for present numerical solutions of the stability problem. Good quantitative agreement of numerical and experimental results promoted analysis of the cases not investigated experimentally till now.
Global stability analysis
The following scheme explains the main steps of the stability analysis:
Real part of the eigenvalue is the growth rate of the disturbance while imaginary one represents non-dimensional frequency.
Disturbance can be calculated with the use of the complex eigenvector. Superposed with the steady flow solution gives the linear approximation of the unsteady flow.