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$$$$ DFDT     NOTICE  CHAT      11/09/12    21:15:52     7124           
                                             DATE     11/09/12
                                                                                
     Operateur DFDT                          Voir aussi : NAVI


     Syntaxe EQEX (cf EQEX) :

     ... 'EQEX' ... 'OPTI' MOT1 MOT2 MOT3 ('INCOD' MOT4)
                    'ZONE' MOD2
                    'OPER' 'DFDT' OBJ1 OBJ2 (OBJ6) OBJ3 (OBJ4) (OBJ5)
                    'INCO' MOT5 (MOT6)




     Description :
     _____________

     DFDT operator discretizes the partial derivative in time term
in a scalar or vectorial equation.

     Transient procedure EXEC use this operator with data
constructed with EQEX operator with the syntax done.


     Contents :
     __________
                                                                                
    'OPTI' : Key word introducing numerical options
     MOT1  : Discretization in space ('EF', 'VF' or 'EFM1')
     MOT2  : Discretization in time ('IMPL')
     MOT3  : Stabilization ('CENTREE','SUPG','SUPGDC')

    'INCOD': Imposition of unknown geometrical support (optional)
     MOT4  : 'CENTRE'

    'ZONE' : Key word introducing geometric informations
     MOD2  : MODEL of subtype 'NAVIER_STOKES' associated to the
             region where DFDT works.

    'OPER' : Key word introducing operator's name and physical data
    'DFDT' : Operator's name treated by EQEX
     OBJ1  : Storage coefficient
             (CHPOINT SCAL [CENTRE or SOMMET] or FLOTTANT or MOT)
     OBJ2  : Inknown at backward time step (CHPOINT or MOT)
     OBJ3  : Time step (FLOTTANT or MOT)
             In the particular case where 'DELTAT' is written for
             OBJ3,DFDT takes the time step in the PASDETPS table.
             This time step is automatically computed for the
             explicit time scheme by operators NS NSKE or TSCA.
     OBJ4  : Velocity for SUPG or SUPGDC option
             (CHPOINT VECT SOMMET or POINT or MOT)
     OBJ5  : Diffusion for SUPG or SUPGDC option
             (CHPOINT SCAL [CENTRE or SOMMET] or MOT)
     OBJ6  : Inknown 2 time steps backward, when BDF2 specified in EQEX
             (CHPOINT ou MOT)
     If MOT3='CENTREE' OBJ4 and OBJ5 are optional.

    'INCO' : Key word introducing primal and dual unknowns' name
     MOT5  : Primal unknown's name
     MOT6  : Dual unknown's name
     As primal=dual, only one is mandatory.


     Remarks :
     ___________
                                                                                
     1) When OBJi is of type MOT, we look for data in INCO table
at the index OBJi.

     2) Geometric support (spg) of CHPOINT is one of those contained
in the 'NAVIER_STOKES' model. Some compatibilities are verified :
   - For EF or EFM1 formulation, dual unknown's spg contain SOMMET
   - For VF formulation, dual unknown's spg contain CENTRE
   - If MOT4='CENTRE', EF and EFM1 formulations are treated as VF
formulation.

     3) When OBJ1 and/or OBJ5 have SOMMET spg, we use the average
value per element of these data to compute the contribution of
DFDT operator.

     4) Graduate user who develops his own transient procedure calls
the DFDT operator with the following syntax :
  B A  =  DFDT TAB1 ;
with TAB1 : Table of subtype EQEX ; contains physical and numerical
            informations ; created by the EQEX operator.
     A    : the mass matrix, stored in a MATRIK
     B    : the tight hand side, stored in a CHPO. CHPO component's 
            name of the dual unknown contribution is MOT6.