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Rotor Dynamics Analysis for Multiple Rotors

Mahmut · 2025-05-21T11:44:30+00:00

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Mahmut

Hello, I have a model that consist of multiple rotor which have different RPM's. These are connected each other with RGB's (Reduction Gear Box). I defined 3 different ROTORG Set for components that have different speed. But under loadstep I can choose just one RGYRO card. As you know RGYRO card includes ROTORG set. Shortly, how can I define the different RPM rotors in one analysis model. Thanks for your responses.

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Adriano_Koga

When multiple rotors are present within the system being modeled, one of the rotors is chosen as a reference rotor. The speeds of the rest of the rotors are linearly dependent of the reference rotor. Scale factors

S1

and

S2

are used to relate the speeds.

(1)

Ω=S1+S2*ΩrefΩ=S1+S2*Ωref

Where,ΩSpeed of a rotor (different from the reference rotor)S1 and S2Scale factorsΩrefSpeed of the reference rotor

https://2021.help.altair.com/2021/hwsolvers/os/topics/solvers/os/rgyro_bulk_r.htm

Mahmut

Thanks for your answer. I had reviewed the part you posted in the help section. Actually, what I was wondering was if we examine the ROTOR_1, ROTOR_2 and ROTOR_3 set with SPTID values of 1.0, 2.0 and 3.0 respectively; let's take the ROTOR_1 set as a reference. I also defined the RSPEED card that includes RPM increases in a certain range. When the RSPEED value is 3000 RPM, the speed values for ROTOR_2 and ROTOR_3 will be 6000 RPM and 9000 RPM, is that correct?

If so, when I select the ROTOR_3 set as a reference and in the same way when the RSPEED value is 3000 RPM; will the speed values for ROTOR_1 and ROTOR_2 be 1000 RPM and 2000 RPM, respectively?

Finally, I could not fully understand from the help section in which cases the DDVAL definition is necessary in rotor dynamics. I would be very happy if you could make an explanation for this, thank you, good work.