Abstract: Wake induced vibration is a common phenomenon in the field of aeroelasticity which can cause forced vibrations of the structure. This phenomenon can endanger the integrity and the fatigue life of the excited structure. In this paper, wake induced vibration is studied by an approximate model with upstream cylinder and downstream blade. The cylinder in freestream produces Karman vortex street with a specific frequency. When the cylinder wake encounters the downstream blade, continuous pulse excitation is applied to the blade. Two-dimension numerical simulation based on Fluent illustrates the shedding vortex and transient process of blade from static to vibration at its natural frequency, and the detail information of transient flow field is obtained. Based on the unsteady transient results, proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD) are applied for the decomposition and the reconstruction of the pressure field near the vibrating blade. The modal frequency and the evolution process are extracted to capture the main flow structure of wake induced vibration. The comparison of two modal analysis methods shows that POD reconstruction has a smaller maximum residual than DMD, and DMD has more advantages in single frequency mode extraction and corresponding evolution analysis.

Key words: wake induced vibration; transient process; proper orthogonal decomposition (POD); dynamic mode decomposition (DMD)