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Flow induced vibration in boilers
Tube vibration due to vortex shedding
The vortex formation is periodic & is a
function of the fluid velocity. The tube is
subject to alternating lift forces.
The frequency at which the vortex is
formed and shed, if coincides with tube
natural frequency, the tube would vibrate.
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tacoma bridge.mpeg
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
Turbulent buffeting
Even when the karman vortices are not formed, the fluid flow produces fluctuating forces, having various frequency modes that act on tubes and force them to oscillate.
Tube oscillate in the fluid in a selective forced oscillation mode at their natural frequency.
Vibration modes
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