Analyzing Large Models with Creo Elements/Direct Finite Element Analysis

For larger models (above 80000-100000 nodes) it is necessary to adjust some memory and scratch settings for NASTRAN.

1) NASTRAN Real Memory

To configure the NASTRAN real memory under <install_dir>/documentation/da_customize.html, refer to To configure the NASTRAN real memory.

2) NASTRAN buffsize

Insert/modify buffsize=estimate in your NASTRAN runtime configuration file. See the example below.

As a side effect, this will produce some output in your execjob window like this:

   Estimated buffsize=16385

   Estimated DOF=266657

   Estimated memory=155.4MB

   Estimated disk=1963.5MB

(DOF ... degree of freedom (each node has 3 DOF)

3) NASTRAN Scratch Space

For models above 80000 to 100000 nodes the scratch space required by NASTRAN will exceed 2 GB. This means that your file system needs to support large files, which is true on NTFS file systems.

Splitting scratch space to multiple files:

Note: The following option is not supported, and should only be used as a workaround.

If you cannot get your file system setup to support large files, the following workaround will allow you to split scratch space to multiple files:

In your NASTRAN Runtime Configuration File you can assign multiple files to your scratch space.
Please follow the example listed below. Note: This option may only appear once in all NASTRAN runtime configuration files. Duplicated entries as described below must not be used for this option. Since this option will be machine specific, it is typically done in the user runtime configuration file.

Customizing the Runtime Configuration Files for NASTRAN

MSC/NASTRAN uses a runtime configuration file which allows specification of various NASTRAN options. The order of precedence for duplicated entries is as follows (with number 1 representing the highest precedence):

1) The user RC file: %HOMEDRIVE%%HOMEPATH%\nast705.rcf . This file should be used to define parameters that are applied to all MSC/NASTRAN jobs run by an individual user. The HOMEDRIVE and HOMEPATH environment variables are set automatically on Windows NT systems.

2) The node RC file: <install_dir>\conf\net\<nodename>\nast705.rcf.<nodename> refers to the Windows name of the computer, which does not necessarily correspond with the TCP/IP node name for the computer. This file should be used to define parameters that are applied to all MSC/NASTRAN jobs running on this computer.

3) The system RC file: <install_dir>\conf\nast705.rcf. This file should be used to define parameters that are applied to all MSC/NASTRAN jobs run by an individual user. The HOMEDRIVE and HOMEPATH environment variables are set automatically on Windows systems.

Example NASTRAN Runtime Configuration File

Note:The entries for splitting databases within the runtime configuration file are not supported.

Example RC file:

buffsize=estimate

INIT SCRATCH LOGICAL=(SCR1(1500MB),SCR2(1500MB),SCR3(1500MB),

     SCR4(1500MB)) ,

     SCR300=(SCRA(1000MB),SCRB(1000MB),SCRC(1000MB),

     SCRD(1000MB))

     ASSIGN SCR1='E:\tmp\SCRATCH.scr1'

     ASSIGN SCR2='D:\tmp\SCRATCH.scr2'

     ASSIGN SCR3='C:\tmp\SCRATCH.scr3'

     ASSIGN SCR4='E:\tmp\SCRATCH.scr4'

     ASSIGN SCRA='E:\tmp\SCR300.scr1'

     ASSIGN SCRB='E:\tmp\SCR300.scr2'

     ASSIGN SCRC='E:\tmp\SCR300.scr3'

     ASSIGN SCRD='E:\tmp\SCR300.scr4'