# RSPINR

Bulk Data Entry Defines the relative spin rates between rotors and rotor damping parameters during a rotor dynamic analysis in Static, Modal Complex Eigenvalue or Frequency Response solution sequences.

## Format

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
RSPINR ROTORID GRIDA GRIDB SPDUNIT SPTID
GR ALPHAR1 ALPHAR2 WR3R WR4R WRHR HYBRID

## Example

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
RSPINR 130 2400 2401 FREQ 200
0.03     1000 1500 1200 3

## Definitions

Field Contents SI Unit Example
ROTORID
setid
Rotor identification number.

No default <Integer > 0>

GRIDA Identifies a grid on the Rotor Line Model.

GRIDA and GRIDB define the positive rotor spin direction. The vector connecting GRIDA and GRIDB is the positive direction vector. The rotor axis is defined using the ROTORG Bulk Data Entry and the two grids (GRIDA, GRIDB) are also specified on the ROTORG Bulk Data Entry.

No default <Integer > 0>

GRIDB Identifies a grid on the Rotor Line Model.

GRIDA and GRIDB define the positive rotor spin direction. The vector connecting GRIDA and GRIDB is the positive direction vector. The rotor axis is defined using the ROTORG Bulk Data Entry and the two grids (GRIDA and GRIDB) are also specified on the ROTORG Bulk Data Entry.

No default <Integer > 0>

SPDUNIT
RPM
Specifies that the relative spin rates are input in Revolutions Per Minute.
FREQ
Specifies that the relative spin rates are input in revolutions (cycles) per unit time.

No default

SPTID
<Integer > 0>
If an integer value (must be greater than 0) is input, it references a DDVAL Bulk Data Entry that specifies the relative rotor spin rates. 3
<Real>
If a real number is input, the value is considered constant.

No default <Integer > 0/Real>

GR Rotor structural damping factor. 4 6

Default = 0.0 <Real>

ALPHAR1 Scale factor applied to the rotor mass matrix for Rayleigh damping. 5 6

Default = 0.0 <Real>

ALPHAR2 Scale factor applied to the rotor stiffness matrix for Rayleigh damping. 5 6

Default = 0.0 <Real>

WR3R Average excitation frequency for calculation of rotor damping and circulation terms for rotor structural damping specified through GR field.

Default = 0.0 <Real>

WR4R Average excitation frequency for calculation of rotor damping and circulation terms for rotor structural damping specified through GE (material, bushing etc.) entries.

Default = 0.0 <Real>

WRHR Average excitation frequency for calculation of rotor damping and circulation terms for rotor structural hybrid damping specified through HYBRID entry.

Default = 0.0 <Real>

HYBRID Hybrid damping. References the identification number of a HYBDAMP entry for hybrid damping specification. Can be used to specify frequency-dependent hybrid damping value for each rotor (ROTORID). 6

Default = 0 <Integer ≥ 0>

1. A RSPINR entry must exist for each rotor line model defined using the ROTORG Bulk Data Entry.
2. GRIDA and GRIDB define the positive rotor spin direction. The vector connecting GRIDA and GRIDB is the positive direction vector. The rotor axis is defined using the ROTORG Bulk Data Entry and the two grids (GRIDA, GRIDB) are also specified on the ROTORG Bulk Data Entry.
3. An integer or a real number can be input in the SPTID field. If SPTID is an integer, it references a DDVAL Bulk Data Entry that specifies the relative rotor spin rates. Each rotor must be assigned the same number of spin rates. To determine relative spin rates, the table entries which contain the sequence of spin rates are correlated. The i'th entry for each rotor corresponds to the relative spin rates between rotors at RPMi/FREQi. The spin rates for the reference rotor must be specified in ascending or descending order.
4. Rotor structural damping factor ($GR$ ) can be incorporated as either equivalent viscous damping or structural damping depending on the solution sequence.
(1)
${\left({C}_{R}\right)}_{Structural}=\left(\frac{GR}{WR3}\right){K}_{R}$
Or,(2)
${\left({C}_{R}\right)}_{Viscous}=\left(1+iGR\right){K}_{R}$

Where, WR3 is a parameter defined as a field on RSPINR entry, or by PARAM, WR3. In case both are defined, then WR3 on RSPINR takes precedence. GR is defined as a field on the RSPINR Bulk Data Entry.

The selection depends on the following factors:
• Modal frequency response or Complex eigenvalue analysis
• Synchronous or Asynchronous solutions
• Value of PARAM, GYROAVG
5. The Rayleigh damping value for the rotor is calculated from ALPHA1 and ALPHA2. ${\alpha }_{R1}$ and ${\alpha }_{R2}$ are used to define the Rayleigh viscous damping as:(3)
${\left({C}_{R}\right)}_{Rayleigh}={\alpha }_{R1}{M}_{R}+{\alpha }_{R2}{K}_{R}$
and(4)
${\left({C}_{R}^{C}\right)}_{Rayleigh}={\alpha }_{R1}{M}_{R}^{C}+{\alpha }_{R2}{K}_{R}^{C}$
6. For detailed information on how each type of rotor damping enters into the system equations through their corresponding damping and circulation terms. Refer to Rotor Dynamics in the User Guide.
7. Rotor damping is cumulative and caution should be exercised when multiple damping effects are assigned.