Fluid-structure interaction

Consider that we have a characteristic length D with a natural frequency fs in a flow which velocity is U. Dimensional analysis enables to show a dimensionless number u* which is the reduced velocity. 

This parameter enables us to describe the fluid-structure interaction phenomena, it compares the characteristic time ofthe structure and the characteristic time of advection. By plotting amplitude of oscillation as function of the reduced velocity, we can consider three zones which correspond to different mechanisms :

Figure 1.2 – Amplitude of oscillation as function of reduced velocity

— Zone 1 corresponds to Turbulence Induced Vibrations (TIV). The amplitude is limited and increases steadily with the reduced velocity.

— Zone 2 is the zone of Vortex Induced Vibrations (VIV). It looks like a resonance where natural modes are excited by the wake. Amplitude increases but the system remains stable.

— Zone 3 corresponds to Movement Induced Vibrations (MIV), the system may be unstable and cause the break of the structure. 2