Vmchka.v2004, AN ALTER PACKAGE FOR CHECKING VIRTUAL MASS MODELS

1.  Summary.  

Virtual mass is selected by a MFLUID case control command, which selects 
an MFLUID entry which in turn selects ELISTi entries.  The ELISTi
entries list QUAD4 and  TRIA3 elements that are wetted by the fluid.  

The virtual mass is applied to the "positive" face of the wetted
elements, as described  by the right-hand rule described in the MFLUID
entry of the QRG.  If an element is  ordered the "wrong" way, it can be
changed by putting a minus sign in front of its EID on  the ELISTi
entry.  The fluid may all be on the inside of the wetted surface (the
"tank"),  or outside it, but not with wetted faces on both sides.

It is tedious to inspect all elements for having the "right" face
wetted.  If wrong wetted  faces exist the results may be poor, or the
Lanczos or other eigensolution methods may fail  with messages about
negative mass being present, or other messages implying this condition.  

This alter package lists the number of wetted elements of both the
internally-wetted and  externally-wetted types, and lists the EIDs of
the smaller set.

2.  Input.  

Set up a conventional VM model, for SOL 103.  If the METHOD commands are
commented  out the checks will be performed, but the run will stop
before the expensive eigensolutions are attempted.  

Each MFLUID entry must have a PARAM, VSPHERE, [CID] paired with it.  The
CID must appear on a  CORDiS entry that defines a spherical coordinate
system whose origin is inside the volume of the tank, at a point where
it can "see" all elements.  If the shape of the tank is not convex, and
there is  no point where all elements can be seen because of bends in
the surface, some elements may be  misidentified as being wetted on the
"wrong" side.  If PARAM, VSPHERE is not present a fatal error exit  will
occur.  Baffle elements are wetted on both sides, and listed on ELIST2
entries.  As they can not be  wetted on the "wrong" side, any output for
ELIST2 entries can be ignored, or the ELIST2 entries can  be removed
during checking.

3.  Output.  

The number of elements wetted on the inside and outside are printed.  If
both classes exist,  the shorter list of EIDs are printed.  

4.  Theory.  

The spherical coordinate system is used to transform the area-factor
matrix Gge to  spherical coordinates.  A column of this matrix
corresponds to one of the elements.  If all elements are wetted  on the
same side their T1 component should be of the same sign in this matrix. 
Columns whose signs are  exceptional are noted as likely being in error,
and are identified.  A vector resultant table is printed  out because it
can not be suppressed when converting Gge to spherical coordinates.  It
is not of much use.   The spherical Gge matrix is used only for
checking.  The spherical coordinate system does not affect any  of the
conventional processing.


5.  Example Problem.

File vmchk1.dat has two mfluid entries selected.  In the main bulk data
deck a model that was wetted correctly  has been modified so that one
element has been numbered incorrectly, and four elements have had their
sign changed  on their elist entry, incorrectly.  All 5 element IDs are
identified.  In a part bulk data deck a correct VM model  is present. 
Its output consists only of the number of wetted elements.  They are all
of one type.