Manual pages | Cast3M

$$$$ ALEA     NOTICE  CHAT      11/09/12    21:15:05     7124           
                                             DATE     11/09/12

     Operateur ALEA                          Voir aussi : DCOV BRUI
     --------------   
     OBJ1 = 'ALEA' 'BANDES_TOURNANTES' | MODE1  (MOT1)
                            | MAIL1
            'EXPO' 'SIGMA' FLOT1 ('MOYENNE' FLOT2)
                   |  'LAMBDA' FLOT3 
                   |  'LAMBDA1' FLOT4 (VEC4) 
                     ('LAMBDA2' FLOT5 (VEC5))
                     ('LAMBDA3' FLOT6 (VEC6))


        Purpose :
        ---------

        Generation of a gaussian, stationary (constant mean, standart
        deviation and correlation function), random scalar field
        using the turning band method. 
        This field has an isotropic, exponential covariance.
        The covariance matrix is :

        Cij = s² * EXP ( - (d1²/l1² + d2²/l2² + d3²/l3²) ** .5 )

        where s is the standard deviation,
          (d1,d2,d3) are the coordinates of the vector linking
          Pi and Pj two mesh points.
          (l1,l2,l3) are the correlation lenghs along the 3 directions.


        Contents :
        ----------

    'BANDES_TOURNANTES'
             : key word indicating the use of the turning band method.
               tournantes (the only method availabe yet in this
               operator ; see 'DCOV' and 'BRUI' pour the matrix method).

       MODE1 : model on which the resulting field is defined
               (MMODEL type), indicates that an element field is
               expected on the output.

        MOT1 : facultative key word among 'NOEUD','GRAVITE','RIGIDITE',
               'MASSE','STRESSES'
               indicating the points to be taken into account for the
               generating of the field, default = 'NOEUD'.
               The options 'RIGIDITE','MASSE','STRESSES' require a
               mechanics model, whereas the option 'GRAVITE' requires
               a 'NAVIER-STOKES' or 'DARCY' model.
               
       MAIL1 : Mesh on which the resulting field is defined (type 
               MAILLAGE), indicates that a point field is
               expected on the output.

      'EXPO' : key word for an exponential covariance function.

     'SIGMA' : key word followed by :

       FLOT1 : standard deviation of the field to be generated 
               (FLOTTANT type).

   'MOYENNE' : optional key word followed by :
 
       FLOT2 : mean of the random field (type FLOTTANT), default = 0. 
 
    'LAMBDA' : key word for an isotropic correlation function,
               followed by :

       FLOT3 : isotropic correlation length (FLOTTANT type).

   'LAMBDA1' : key words for an anisotropic correlation function.
  ('LAMBDA2')  they are as many as the dimension of the correlation, 
  ('LAMBDA3')  and are respectively followed by :

       FLOT4 : lanisotropic correlation lengths (type FLOTTANT) in the 3
      (FLOT5)    
      (FLOT6)  main directions.

      (VEC4) : optionnal directions of the main 1,2 and 3
      (VEC5)   correlation axis respectively (type POINT).
      (VEC6)   They must be non-nul and perpendicular. 
               default = axis (1 0 0), (0 1 0) and (0 0 1).

        OBJ1 : generated field (CHPOINT or MCHAML type
               according to the presence of a mesh or a model inthe
               input), nature 'DIFFUS', one component 'SCAL'.

         
        Remarks :
        ---------

           1.  The quality of the result is directly dependent on the
               regularity of the input mesh and its consistency with the
               possible correlation anisotropy.
               No verification is made about this regularity.