Stiffness of gaps in rotordynamics
Stiffness of gaps in rotordynamics
(OP)
Hy,
I start in rotordynamics and are a little bit confused of the stiffness of gaps.
The situation is: a rotating shaft (d=200mm) with a small gap (1mm) to the stationary part. No fluid flow across the gap (only in tangential direction of course)
Calculated according to Black, I get negative kxx and kyy and very high additional masses. Is this realistic ? How do you handle the influence of such gaps ?
If I take them as journal bearings, I would get positive stiffness and no additional masses from our "journal bearing program"
Thanks
Chris
I start in rotordynamics and are a little bit confused of the stiffness of gaps.
The situation is: a rotating shaft (d=200mm) with a small gap (1mm) to the stationary part. No fluid flow across the gap (only in tangential direction of course)
Calculated according to Black, I get negative kxx and kyy and very high additional masses. Is this realistic ? How do you handle the influence of such gaps ?
If I take them as journal bearings, I would get positive stiffness and no additional masses from our "journal bearing program"
Thanks
Chris





RE: Stiffness of gaps in rotordynamics
RE: Stiffness of gaps in rotordynamics
thanks for your answer. I still have problems to understand:
1.) Where is the difference between Black, Fritz ... with decentrating forces and on the other side the journal bearing theory with centrating forces ? If I have a gap that isn't defined as journal bearing, which theory could be applied ??
2.) If I have additional inertial masses in my model, the weight of the complete machine is about 10x higher than in reality. So the pendular frequency of the whole machine changes dramatically compared to the machine, when the shaft does not rotate and no inertia forces exist. Is this reality ?
Thanks
chris
RE: Stiffness of gaps in rotordynamics
RE: Stiffness of gaps in rotordynamics
Has anyone done more recent testing with density or are they continuing with fluid-states?
RE: Stiffness of gaps in rotordynamics