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Modal computation of a tank in NX Nastran using the MFLUID feature

Experimenter
Experimenter

Hi,

 

I am trying to run a 103 modal computation of a filled tank.

The computation run without problem without the fluid content.

 

Now added the fluid including following entries in the deck file

(the attached image helps to understand the entries):

 

$RSMETHOD for dry modes

RSMETHOD = 13100

$METHOD for wet modes

METHOD = 13200
MFLUID=200

...

BEGIN BULK
$*  NX Modeling Object: EIGRL 1
EIGRL      13100        200.0000
EIGRL      13200         50.0000

...

PARAM      VMOPT       2

...

$ Entry for the outer shells (only wetted on one side, inside)

$ red part and outside yellow parts in the attached image

MFLUID       200       1 3.0e+02 1.0e-06      11               N       N

$ Entry for 2 inner shells (wetted on both sides)

$ inside yellow parts in the attached image
MFLUID       200       1 3.0e+02 1.0e-06              12       N       N

$

$ coordinate system for the MFLUID entries

CORD2R         1       0 5325.26-788.274520.6972 5325.26-788.274521.6972+

+        5326.26-788.274520.6972

...

$ Element list for the wetted on one side elements
ELIST         11     639     641     644     646     650     653     655+
+            657     658     662     665     666     667     669     670+

...

$ Element list for the both wetted side elements
ELIST         12   29058   29060   29061   29062   29063   29064   29065+
+          29070   29073   29074   29075   29077   29078   29079   29082+

 

 

The computation is not running and following error message appears:

 

 *** SYSTEM FATAL MESSAGE 3034 (LNNHERR)
     INTERNAL FAILURE IN THE LANCZOS PROCEDURE:
     M-ORTHOGONAL QR PROCEDURE FAILED TO CONVERGE.  PROBABLE CAUSE:
     MASS MATRIX IS INDEFINITE (MODES) OR STIFFNESS MATRIX IS INDEFINITE (BUCKLING).
     USER ACTION: CONTACT SIEMENS PLM SOFTWARE CUSTOMER SUPPORT.
 *** SYSTEM FATAL MESSAGE 7340 (LNNHERR)
     WARNING REPORTED BY SUBROUTINE LNNDRVD  (IER=   728)
     USER INFORMATION:  GRAM-SCHMIDT DID NOT CONVERGE.

 TABLE OF SHIFTS:  (LNNRIGL)
 SHIFT #        SHIFT VALUE         FREQUENCY, CYCLES     # EIGENVALUES BELOW    # NEW EIGENVALUES FOUND
     1.        9.8696039E+04          5.0000000E+01                31                        9
     2.       -4.1670943E-04         -3.2489032E-03                 0                       10
     3.        4.9348020E+04          3.5355335E+01                31                        0

 *** SYSTEM FATAL MESSAGE 7340 (LNNRIGL)
     TRIDIAGONAL QL DID NOT CONVERGE.
     THIS RUN IS TERMINATED. PARAM,BAILOUT,-1 MAY BE USED TO CONTINUE THE RUN.

0FATAL ERROR
1                                        * * * END OF JOB * * *
 

 

Maybe I made an error in the MFLUID definition?

I used for example the same coordinate system 1 for both MFLUID definition.

 

Thank you in advance for any hints.

Best regards

Sébastien

 

 

3 REPLIES

Re: Modal computation of a tank in NX Nastran using the MFLUID feature

Siemens Genius Siemens Genius
Siemens Genius

You can try one of the following to see if that helps to get around the error

 

1. Add "sys426=1" to the nastran command line (selects REDMULT performance method)

2. Add "sys263=6" or "sys263=15" (changes the MAXSET of the EIGRL card from the default of 7)

 

Let us know if this resolves your issue


Thanks

Re: Modal computation of a tank in NX Nastran using the MFLUID feature

Experimenter
Experimenter
 

Re: Modal computation of a tank in NX Nastran using the MFLUID feature

Experimenter
Experimenter

Hi,

thank you very much for your quick answer and the hints.

In the meantime I could run the computation without error message (reviewing the MFLUID deck entries like coordinate systems, etc).

 

Kind regards

Sébastien