Damping (SOL 414)

In all SOL 414 solution types, you can apply viscous and hysteretic damping to various parts of the model.

• Viscous damping can be applied to the different parts of the rotor assembly (rotor, stator, connection elements, or superelements).

• Hysteretic damping can be applied to connection elements, rotor, stator, and superelements.

Damping parameters

You can set damping options at the component level and at the solution level.

• At the component level (material, 1D connections, and rotor regions), you can apply the following options:*Structural Damping Coefficient (GE)Reference Frequency W3Reference Frequency W4*

• At the solution level, you can apply the following options:**Overall Structural Damping (G)****Overall Structural Damping Dominant Frequency (W3)****Element Structural Damping Dominant Frequency (W4)**Rayleigh Damping (ALPHA1) and Rayleigh Damping (ALPHA2)

Hysteretic and viscous damping calculations

In SOL 414,110, SOL 414,111, SOL 414,129, and SOL 414,103, you can use the following parameters:

• Overall Structural Damping (G)

• Structural Damping Coefficient (GE)

• Overall Structural Damping Dominant Frequency (W3)

• Element Structural Damping Dominant Frequency (W4)

Rayleigh damping

You can use Rayleigh Damping (ALPHA1) and Rayleigh Damping (ALPHA2) in SOL 414,110, SOL 414,111, SOL 414,129, and SOL 414,103 solutions.

Damping at connection elements

You can apply viscous or hysteretic damping to CBUSH, CBUSH2, and CBEAR2 1D connections.

Damping on rotors (SOL 414,110 and SOL 414,111)

In SOL 414,110 complex modal analysis and SOL 414,111 harmonic response, use the following table to understand the effects of damping on the rotor (ROTORD) reference frequencies when you set:

• Overall Structural Damping (G).

• Structural Damping Coefficient (GE) on the material with no superelements, or Structural Damping Coefficient (GE) for SOL 414,103 superelements.

Rotor reference frequency combination	No rotor superelement	Rotor superelement
Reference Frequency (W3) = 0Reference Frequency (W4) = 0	Damping is only hysteretic.Damping = Hyst(PARAM G + MAT1 GE)	Damping is only hysteretic.Damping = Hyst(PARAM G + SEDAMP GE)
Reference Frequency (W3) > 0Reference Frequency (W4) > 0	Damping is only viscous.Damping = Visc(PARAM G/ROTORD W3 + MAT1 GE/ROTORD W4)	Damping is only viscous.Damping = Visc(PARAM G/ROTORD W3 + SEDAMP GE/ROTORD W4)
Reference Frequency (W3) > 0Reference Frequency (W4) = 0	Damping is only viscous.Damping = Visc(PARAM G/ROTORD W3)There is no contribution from Structural Damping Coefficient (GE) (MAT1 GE) on the material.	Damping is hysteretic and viscous.Damping = Hyst(SEDAMP GE) + Visc(PARAM G/ROTORD W3)
Reference Frequency (W3) = 0Reference Frequency (W4) > 0	Damping is only viscous.Damping = Visc(MAT1 GE/ROTORD W4)There is no contribution from Overall Structural Damping (G) (PARAM G).	Damping is hysteretic and viscous.Damping = Hyst(PARAM G) + Visc(SEDAMP GE/ROTORD W4)

Note:

In SOL 414,129 transient response solutions, all hysteric contributions are equal to zero.

Damping on stators (SOL 414,110 and SOL 414,111)

In SOL 414,110 complex modal analysis and SOL 414,111 harmonic response, use the following table to understand the effects of damping on the stator damping parameters (Parameters page in the Solution dialog box) when you set:

• Overall Structural Damping (G).

• Structural Damping Coefficient (GE) on the material with no superelements, or Structural Damping Coefficient (GE) for SOL 414,103 superelements.

Solution damping parameters combination	No stator superelement	Stator superelement
Overall Structural Damping Dominant Frequency (W3) = 0Element Structural Damping Dominant Frequency (W4) = 0	Damping is only hysteretic.Damping = Hyst(PARAM G + MAT1 GE)	Damping is only hysteretic.Damping = Hyst(PARAM G + SEDAMP GE)
Overall Structural Damping Dominant Frequency (W3) > 0Element Structural Damping Dominant Frequency (W4) > 0	Damping is only viscous.Damping = Visc(PARAM G/ PARAM W3 + MAT1 GE/ PARAM W4)	Damping is only viscous.Damping = Visc(PARAM G/ PARAM W3 + SEDAMP GE/ PARAM W4)
Overall Structural Damping Dominant Frequency (W3) > 0Element Structural Damping Dominant Frequency (W4) = 0	Damping is hysteretic and viscous.Damping = Hyst(MAT1 GE) + Visc(PARAM G/ PARAM W3)	Damping is hysteretic and viscous.Damping = Hyst(SEDAMP GE) + Visc(PARAM G/ PARAM W3)
Overall Structural Damping Dominant Frequency (W3) = 0Element Structural Damping Dominant Frequency (W4) > 0	Damping is only viscous.Damping = Visc(MAT1 GE/ PARAM W4)There is no contribution from Overall Structural Damping (G) (PARAM G).	Damping is hysteretic and viscous.Damping = Hyst(PARAM G) + Visc(SEDAMP GE/ PARAM W4)

Note:

In SOL 414,129 transient response solutions, all hysteric contributions are equal to zero.

Where do I find it?

Defining damping for a rotor dynamics solution

Application	Pre/Post
Prerequisites	A Simulation file as the work part and displayed partSimcenter Nastran as the specified solverRotor Dynamics as the specified analysis type
Command Finder	Solution
Simulation Navigator	Right-click an active solution→Edit
Location in dialog box	Solution dialog box→Parameters page→Damping group

Defining damping for a rotor region

Application	Pre/Post
Prerequisites	A Simulation file as the work part and displayed partSimcenter Nastran as the specified solverRotor Dynamics as the specified analysis typeOne of the following as the specified solution type:SOL 414,103 Eigenvalues and Superelement ReductionSOL 414,110 Complex Modal AnalysisSOL 414,111 Harmonic Response****SOL 414,129 Transient Response
Command Finder	Define Rotor Region
Simulation Navigator	Under the Regions node, right-click a region→Edit
Location in dialog box	Region dialog box→Parameters (ROTORD) group→Reference Frequency W3 or Reference Frequency W4

Defining damping for materials

Application	Pre/Post
Prerequisites	A Simulation file as the work part and displayed partSimcenter Nastran as the specified solverRotor Dynamics as the specified analysis type
Command Finder	Manage Materials
Simulation Navigator	Right-click an active solution→Edit
Location in dialog box	Manage Materials dialog box→Type list→Isotropic→Create material→Property View list→Simcenter Nastran MAT1→Mechanical page→Structural Damping Coefficient (GE)

How do I

Create connection elements between coincident nodes with CBEAR2 elements

Define rotor bearing or bushing properties

Create a rotor region

Define a rotor

Define the rotor dynamics solution parameters

Create an unbalance mass

Define forcing frequencies

Define nonlinear transient parameters

Set the duration of the simulation

Create a modeling object

Assign a modeling object to a solution or solution subcase

Learn more

Rotor dynamic analysis (SOL 414)

Modeling axisymmetry (SOL 414)

Modeling cyclic symmetry (SOL 414)

Creating connection elements on a rotor model (SOL 414)

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Damping (SOL 414), Simcenter 3D 2021.1 Series

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