/EIG
Block Format Keyword Defines the eigen modes and static modes computation for flexible bodies.
Format
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/EIG/eig_ID/unit_ID  
eig_title  
grnd_ID  grnd_bc  Trarot  Ifile  
Nmod  Inorm  Cutfreq  Freqmin  
Nbloc  Incv  Niter  Ipri  Tol  
Filename 
Definition
Field  Contents  SI Unit Example 

eig_ID  Mode
identifier. (Integer, maximum 10 digits) 

unit_ID  Unit Identifier. (Integer, maximum 10 digits) 

eig_title  Mode title. (Character, maximum 100 characters) 

grnd_ID  Node group to which the
modes will be computed.
(Integer) 

grnd_bc  Node group to which
specific eigen modes are applied. 3
(Integer) 

Trarot  Codes for translations and
rotations. (6 Booleans) 

Ifile  Additional modes file
flag. 5 (Integer) 

Nmod  Maximum number of modes to
be computed. Default = 100 (Integer) 

Inorm  Eigenvector normalization
method flag.
(Integer) 

Cutfreq  Maximum eigen frequency.
(Real) 
$\text{[Hz]}$ 
Freqmin  Minimum eigen frequency.
7
Default = 0.001 Hz (Real) 
$\text{[Hz]}$ 
Nbloc  Number of eigen modes per
block. 9
(Integer) 

Incv  Factor to obtain the
number of Lanczos basis vectors to use throughout the computation.
10 Default = 2 (Integer) 

Niter  Maximum number of Arnoldi
iterations. Default = 300 (Integer) 

Ipri  Printout level for
ARPACK. Default = 0 (Integer) 

Tol  Relative accuracy to which
eigen values are to be computed.
Default = 0.0 (Real) 

Filename  Additional modes file
name. (Character, maximum 100 characters) 
Comments
 This functionality is implemented for the purpose of the generation of flexible bodies. For detailed normal modes analysis of a model the use of the Bulk Data Format is strongly recommended.
 The use of the implicit option /IMPL/LINEAR in the Radioss Engine is required to compute normal modes.
 Boundary condition corresponding to the
codes for translations and rotations are added to these nodes for the computation of
eigen modes. Static modes, one for each additional blocked DOF, are computed.
A static mode corresponds to the static response of the structure, all DOF of the set of interface nodes concerned by additional boundary conditions being blocked; except one taking the one value.
 The codes for translations and rotations follow the same rule as for the /BCS option.
 If Ifile ≠ 0: An
additional file is provided containing precomputed modes from a normal modes
analysis, either experimental or numerical. These modes are used to reduce the
dimension of the space in which eigenvalues are sought and thus enhance
efficiency.
If Ifile = 1, the additional file is given in a format defined in External Modes File.
 Multilevel condensation is no longer supported.
 The default (if set blank or zero) for Freqmin is 0.001 Hz. If a value other than zero is entered, that value defines a frequency in the unit system set for /EIG. The capability of computing rigid body modes is not fully implemented. It is recommended to either sufficiently constrain the model or to select a value for Freqmin that is high enough to eliminate all rigid body modes.
 Eigen modes are computed using ARPACK software (R. Lehoucq, K. Maschhoff, D. Sorensen, C. Yang).
 Better precision is achieved when only a small number of eigen modes are computed simultaneously.
 The number of Lanczos basis vectors to use
through the course of the computation is given from the number of required
eigenvalues per block (or total if Nbloc = 0) by
the formula:
N_{Lanczos vectors} = N_{required eigenvalues} * Incv.
 For the postprocessing of modes shapes in HyperView, Radioss Starter input file (*000.rad) should be chosen in the Load Model panel and the first output animation file (*A001 which contains the first mode) in the Load Result panel.