#123: Difference between OP2 and enhanced OP2

Sep 28, 2020 | nastran

#122: Difference between OP2 and enhanced OP2

There are two formats of OP2 that Nastran can generate. There is the old-style OP2 that is generated when you have PARAM, POST, -1 in the input deck and can only be read into Patran using the ‘Read OP2’ option. The results from the regular OP2 are imported and stored in the db, which can cause problems for large amounts of data.

The other format is the Enhanced OP2 that is generated when you have PARAM,POST,1 in the input deck. As of Patran 2013, this is written by default when you request op2 output.

Here are some key features of Enhanced OP2:

1) It does not store the results in the Patran db, hence the db size does not increase. This feature is similar to XDB and hence is more efficient.
2) It can store contact results which the regular OP2 can not.
3) In the background Patran converts the enhanced OP2 to MASTER/DBALL and attaches it. For large op2 files this process can take a significant amount of time, and it will repeat it each time the db with the attachment is opened. For this reason it’s usually better to request MASTER/DBALL results directly rather than enhanced op2.
4) File size is not as large as the Master/DBall.
5) Does not run into DBC issues like XDB.