Compute new variables

Your description file must contain these new variables descriptions.

Let's define the syntax of these variable definitions; then in each type of description file, we indicate if the format supports or not new variable definition.

For each format supporting the definition of new variables, the user must specified the functions used, the name affected to the new variables and functions arguments at the end of the description file as specified here:

• neg:

  Syntax:

  neg: new_scal_name old_scal_name

  The scalar variable new_scal_name is added with values obtained by the negation of the values of the scalar variable old_scal_name.

  Exemple:

  neg: u u2

• scale:

  Syntax:

  scale: new_scal_name old_scal_name scale

  The scalar variable new_scal_name is added with values obtained by the multiplication of the values of the scalar variable old_scal_name by the constant scale.

  Exemple:

  scale: u u2 -1.2

• vect2d:

  Syntax:

  vect2d: vect_name x_scal_name y_scal_name step

  The vector variable vect_name is added with the previously defined scalars variables components x_scal_name and y_scal_name and the scalar constant step associated.

  Exemple:

  vect2d: vitesse u v 1.e-6

• vect3d:

  Syntax:

  vect3d: vect_name x_scal_name y_scal_name z_scal_name step

  The vector variable vect_name is added with the previously defined scalars variables components x_scal_name, y_scal_name and z_scal_name and the scalar constant step associated.

  Exemple:

  vect3d: vitesse u v w 1.e-7

• div2:

  Syntax:

  div2: a b c

  The scalar variable a is added, computed from the previously defined scalar variables b and c by: $a = b / c$

• veclen:

  Syntax:

  veclen: l v

  The scalar variable l is added, computed from the previously defined vector variable v by: $l = \Vert v\Vert$

• pressure:

  Syntax:

  pressure: p V E rho gamma

  The scalar variable p is added, computed from the previously defined vector variable V, scalars variables E and rho and the constant gamma by:
  

  $$p = (\gamma - 1) ( E - {1\over 2}\rho\Vert V\Vert^2)$$
  
  

• mach:

  Syntax:

  mach: mach ||V|| p rho gamma

  The scalar variable mach is added, computed from the previously defined scalars variables ||V|| p and rho and the constant gamma by:
  

  $$Mach = \sqrt{\frac{\rho \Vert V\Vert^2}{\gamma p}}$$
  
  

Here are examples of description files for each formats: