VELOCITY
I/O Options and Subcase Information Entry The VELOCITY command can be used in the I/O Options or Subcase Information sections to request velocity vector output for all subcases or individual subcases, respectively.
Attention: Valid for Implicit
and Explicit Analysis
Format
VELOCITY(sorting,format,form,rotations,random,peakoutput,type,fourier,statistics, SUBSYS) = option
Definitions
| Argument | Options | Description |
|---|---|---|
| sorting | <SORT1, SORT2> | 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.
|
| format | <HM, H3D, OPTI,PUNCH, OP2, HG, PLOT, HDF5, blank> Default = blank |
|
| form | <COMPLEX, REAL,
IMAG, PHASE,
BOTH> Default (HM only) = COMPLEX Default (all other formats) = REAL |
|
| rotations | <ROTA, NOROTA> |
|
| random | <PSDF,
RMS, PSDFC> No default |
Output is available in the .h3d, and
.h5 formats. 5
|
| peakoutput | <PEAKOUT> Default = blank |
If PEAKOUT is present, only the filtered frequencies from the PEAKOUT card will be considered for this output. |
| type | <NORMAL> |
|
| FOURIER | <FOURIER> | |
| statistics | <STATIS, OSTATIS, or blank> | Results of Velocity Statistics over time in a Transient Analysis
are controlled by this option. 15
|
| SUBSYS | <SUBSYS_ID> 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 = YES |
|
Comments
- When the VELOCITY command is not present, velocity vector is not output.
- Velocity output is available for frequency response and
transient analysis solution sequences.
Velocity output is available by default for Darcy Flow Analysis subcases and can be controlled using the VELOCITY command. Velocity for flow analysis is only available in H3D files and can be visualized as “Element Velocity for Flow (v)” in HyperView.
For Darcy Flow Analysis:- VELOCITY I/O Entry accepts either YES/ALL or GRID SETs as input.
- For Darcy flow, any elements attached to the GRID IDs in the specified GRID SET will have their elemental velocity output printed.
- ELEMENT SET based identification is not supported for the VELOCITY I/O Entry.
- In the example illustrated below, choosing SET 12 for VELOCITY
results will output Darcy flow velocity for the following 8
CHEXA elements.
VELOCITY = 12 BEGIN BULK SET,12,GRID,LIST +, 3802, 9452Figure 1. Darcy flow velocity example 
- The form argument is only applicable for Frequency Response Analysis. It is ignored for other analysis types.
- The forms BOTH and COMPLEX do not apply to the .frf output files.
- 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 information on the results available and their respective formats.
- Multiple instances of this card are allowed. If instances are conflicting, the last instance dominates.
- For optimization, the frequency of output to a given format is controlled by the I/O option OUTPUT.
- 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.
- 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/IMAG format to the required formats. Results in ASCII formats are output in the specified/requested FORM.
- The four-letter abbreviation VELO is interchangeable with VELOCITY.
- format=OUTPUT2 can also be used to request results to be output in the Nastran output2 format (.op2 file).
- For NORMAL velocity output, the surface grids are automatically selected from within the specified GRID SET. Alternately, if option=ALL is input, the normal velocity is output for all surface grids in the model. Normal results are only available for Frequency Response Analysis and in the H3D format.
- The FREQ and TIME options are only valid for Modal Transient Analysis with Fourier transformation. When FREQ is present, the velocities in frequency domain would be output in a dummy frequency subcase, which shares the same ID with the transient subcase.
- The HDF5 output is printed to a .h5 binary results file. For details of the supported analysis types and elements when the .h5 output format is requested, refer to the .h5 file.
- Velocity statistics are supported for
Direct and Modal Linear Transient Analysis types.
Only H3D output is supported for velocity statistics.
The following statistics over time are output for Transient Analysis when STATIS or is specified.- Statistics
- Supported Velocity 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 velocity 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 Velocity (Statistics) (s).Figure 2. 