Normal Modes Abnormally Terminates With MFLUID

[Anonymous]

I'm learning how (or trying to) to use the MFLUID entry to account for fluid mass in some normal modes analysis.  I created a very simple box with an open top, and I did a basic free-free normal modes analysis.  I then created a region for the box's four vertical sides and bottom for the MFLUID (the fluid being seawater).  I did a "dry" normal modes analysis to establish a baseline, and everything went well.  When I try the "wet" normal modes analysis (with the MFLUID region defined), Autodesk Nastran (2018) abnormally terminates.  I checked the .OUT file for any errors and warnings.  None exist other than it terminates abnormally.

I don't know what is going wrong or what I'm missing.  It is probably something too obvious for me to notice. 

I have attached the BDF/analysis file.

Autodesk Nastran version 2018

Femap version 11.4.2

[John_Holtz · Accepted solution]

Hi everyone.

The problem is the LANCZOS extraction method has a problem when MFLUID is included in the analysis. The solution is to change the extraction method to SUBSPACE.