Flow induced vibration in boilersFlow induced vibration in boilers

Tube vibration due to vortex shedding Tube vibration due to vortex shedding

The vortex formation is periodic & is a The vortex formation is periodic & is a function of the fluid velocity. The tube is function of the fluid velocity. The tube is subject to alternating lift forces. subject to alternating lift forces.

The frequency at which the vortex is The frequency at which the vortex is formed and shed, if coincides with tube formed and shed, if coincides with tube natural frequency, the tube would vibrate.natural frequency, the tube would vibrate.

Click below Click below

The fluid flow causes tube to be displaced from its initial posotion. This displacement causes a further shift in flow field changing the fluid force acting in the tubes.

Fluid elastic vibration Fluid elastic vibration

Turbulent buffetingTurbulent buffetingEven when the karman vortices are not Even when the karman vortices are not

formed, the fluid flow produces fluctuating formed, the fluid flow produces fluctuating forces, having various frequency modes forces, having various frequency modes that act on tubes and force them to that act on tubes and force them to oscillate. oscillate.

Tube oscillate in the fluid in a selective Tube oscillate in the fluid in a selective forced oscillation mode at their natural forced oscillation mode at their natural frequency.frequency.

Vibration modesVibration modes