Hello world,
I am performing dynamic analysis on the rotating cantilever beam. With the help of mathematical model I have calculated the natural frequency for axial and two transverse direction that seems to vary with the rotating speed of the beam. The attached file show the variation of natural frequency .
I am clueless with the physics behind the variation?
Is it necessary to decrease axial natural frequency with increase in speed and increase of other two directional frequencies ??
Help me to draw the conclusion.
I think you need to give a bit more information on the use of this. 200000 o/min is very fast spinning. Is this fan blades?
If you have made a matematical model for what happens, then you should know what you have put into it.
A method to test models is to do measurements.
Anders Buen Thank you for your concern.
Actually I have made a mathematical model and it shows in equations too ,about the decrease and increase in the stiffness . The cause for natural frequency change is the stiffness because I have neglected the damping terms.
But I am quit clueless about the physics behind this graph .
Ps: The large speed was just used to check the the variation in stiffness.
Hello Amrit.
I have not yet worked on the vibration of rotating beams. But the effect of the rotation would be to induce longitudinal (along the axis of the beam) tensile stress due to the presence of centrifugal force. Due to this induced tension, the beam will offer more resistance to motion (increased stiffness) in the transverse direction.
Therefore, one can expect that the natural frequency for the transverse vibration of a rotating beam is greater than that of a stationary one. Kindly note that I have not considered the Coriolis effect.
Regards,
Jatin
Jatin Poojary Thank you .
What about the effects of Coriolis or damping terms in natural frequency or can called it as damped natural frequency ??
If you have included damping in your model, then it will be the damped natural frequency.
Initially, I got a bit confused regarding the Coriolis effect and connected it with the gyroscopic effect that is encountered in rotor dynamics. But it looks like in the present case the physics is different from that encountered in rotor dynamics. I have not yet studied this topic so at present I am unable to account for their effects. I will update the answer if I learn/find anything regarding it.
Regards,
Jatin
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