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:

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'