I/O Options and Subcase Information Entry The ACCELERATION command can be used in the I/O Options or Subcase Information sections to request acceleration vector output for all subcases or individual subcases, respectively.

Attention: Valid for Implicit and Explicit Analysis


ACCELERATION(sorting,format,form,rotations,random,peakoutput,fourier,type,statistics, SUBSYS) = option


Argument Options Description
sorting <SORT1, SORT2>

Default = blank

This argument only applies to the PUNCH format (.pch file) or the OUTPUT2 format (.op2 file) output for normal modes, frequency response, and transient subcases. It will be ignored without warning if used elsewhere.
Results for each frequency/timestep are grouped together.
Results for each grid/element are grouped together. 8
For Frequency Response Analysis, if grid SET is not specified, SORT1 is used, otherwise, SORT2 is used; for Transient Analysis, SORT2 is used.
format <HM, H3D, HG, OPTI, PUNCH, OP2, PLOT, HDF5, blank>
Results are output in HyperMesh results format (.res file).
Results are output in Hyper3D format (.h3d file).
Results are output in HyperGraph presentation format (_freq.mvw file and _tran.mvw file) - see OUTPUT keywords HGFREQ and HGTRANS.
Results are output in OptiStruct results format (.disp file).
The results can be printed in the old or new OPTI format depending on the analysis type. For more information, refer to PARAM, OPTI.
Results are output in Nastran punch results format (.pch file).
Results are output in Nastran output2 format (.op2 file)
Results are output in Nastran output2 format (.op2 file) when PARAM,POST is defined in the Bulk Data section.
If PARAM, POST is not defined in the Bulk Data section, this format allows the form for complex results to be defined for XYPUNCH output without having other output.
Results are output in the Hierarchical Data Format, Version 5 (.h5 file). 14
blank (Default)
Results are output in all active formats for which the result is available.

Default (HM only) = COMPLEX

Default (all other formats) = REAL

COMPLEX (HM only), blank
Provides a combined magnitude/phase form of complex output to the .res file for the HM output format.
Provides rectangular format (real and imaginary) of complex output. 9
Provides polar format (magnitude and phase) of complex output. Phase output is in degrees.9
BOTH (HM only)
Provides both polar and rectangular formats of complex output.
rotations <ROTA, NOROTA>
Requests output of rotational acceleration results (in addition to translational acceleration results).
NOROTA (Default)
Rotational acceleration results are not output.
random <PSDF, RMS, PSDFC>

No default

Output is available in the .h3d and .h5 formats. 5
Requests PSD and RMS results from Random Response Analysis to be output.
Requests only the RMS result from random response analysis to be output.
Requests PSD, RMS and RMS (cumulative) results from random response analysis to be output.
peakoutput <PEAKOUT>

Default = blank

If PEAKOUT is present, only the filtered frequencies from the PEAKOUT card will be considered for this output.
type <NORMAL>
If present, the normal acceleration results for grids on the surface of shell and solid elements are output. 12
blank (Default)
Normal acceleration results are not output.
Fourier <FOURIER>

Default = blank

Accelerations are output for Modal Transient Response Analysis with Fourier Transformation.
Frequency domain. 13
Time domain. 13
statistics <STATIS, OSTATIS, or blank> Results of Acceleration Statistics over time in a Transient Analysis are controlled by this option. 15
Acceleration Statistics are output in addition to regular acceleration output at each timestep.
Only the Acceleration Statistics are output.
blank (Default)

No default

ID of the subsystem.

When used along a subsystem definition, this option generates an individual result file for each subsystem with results for that subsystem only.

For more information, refer to the SET Bulk Data Entry.
option <YES, ALL, NO, NONE, SID>

Default = ALL

YES, ALL, blank
Acceleration is output for all nodes.
Acceleration is not output.
If a set ID is given, acceleration is output only for nodes listed in that set.


  1. When the ACCELERATION command is not present, acceleration results are not output.
  2. Acceleration output is only available for Frequency Response, Transient Analysis, and Response Spectrum solution sequences.
  3. The form argument is only applicable for Frequency Response Analysis. It is ignored for other analysis types.
  4. The forms BOTH and COMPLEX do not apply to the .frf output files.
  5. Multiple formats are allowed on the same entry; these should be comma separated. If a format is not specified, this output control applies to all formats defined by the OUTPUT command, for which the result is available. See Results Output by OptiStruct for details about supported output formats for different analysis types.
  6. Multiple instances of this card are allowed. If instances are conflicting, the last instance dominates.
  7. For optimization, the frequency of output to a given format is controlled by the I/O option OUTPUT.
  8. In general, HyperView does not recognize the SORT2 format for results from the .op2 file. When results are output only in SORT2 format (<Result Keyword> (SORT2, OUTPUT2, ...)), the results are written by OptiStruct into the .op2 file in SORT2 format, but when the .op2 file is imported into HyperView, the results in SORT2 format are not recognized. Therefore, the SORT1 option is recommended for results output in OUTPUT2 format and SORT2 option is recommended for results output in PUNCH format.
  9. Results in binary format (.h3d or .op2) are always output in PHASE/MAG form, regardless of the options specified in the FORM field. The corresponding post-processors (HyperView/HyperGraph) can easily convert the PHASE/MAG format to the required formats. Results in ASCII formats are output in the specified/requested FORM.
  10. The abbreviations ACCE and ACCEL are interchangeable with ACCELERATION.
  11. format=OUTPUT2 can also be used to request results to be output in the Nastran output2 format (.op2 file).
  12. For NORMAL acceleration output, the surface grids are automatically selected from within the specified GRID SET. Alternately, if option=ALL is input, the normal acceleration is output for all surface grids in the model. Normal results are only available for Frequency Response Analysis and in the H3D format.
  13. The FREQ and TIME options are only valid for Modal Transient Analysis with Fourier transformation. When FREQ is present, the accelerations in frequency domain would be output in a dummy frequency subcase, which shares the same ID with the transient subcase.
  14. The HDF5 output is printed to a .h5 binary results file. Refer to the .h5 file for details of the supported analysis types and elements with the .h5 output format.
  15. Acceleration Statistics are supported for Direct and Modal Linear Transient Analysis types.

    Only H3D output is supported for Acceleration Statistics.

    The following statistics over time are output for Transient Analysis when STATIS or OSTATIS is specified with Acceleration.
    Supported Acceleration Result Types
    Minimum and Time of Minimum
    X-component, Y-component, Z-component
    Maximum and Time of Maximum
    Magnitude, X-component, Y-component, Z-component
    Absolute Maximum and Time of Absolute Maximum
    X-component, Y-component, Z-component
    Arithmetic Mean, Root Mean Square (RMS), Variance, and Standard Deviation
    Magnitude, X-component, Y-component, Z-component
    The acceleration statistics can be viewed in HyperView after loading the H3D file, under Statistics over time option at the end of the timestep list in the Results Browser. Then, various statistics can be chosen from the sub-menu under Acceleration (Statistics) (s).
    Figure 1.