This information is part of the Modelica Standard Library maintained by the Modelica Association.

Declare flow (through) variable, which have to sum up to zero in connections

Examples

connector Pin
  Modelica.SIunits.Voltage v;
  flow Modelica.SIunits.Current i;
end Pin;

model A
  Pin p;
end A;

model Composition
  A a;
  A b;
  A c;
equation
  connect(a.p, b.p);
  connect(a.p, c.p);
end Composition;

From the connect statements in model Composition, the following connect equations are derived:

a.p.v = b.p.v;
a.p.v = c.p.v;
a.p.i + b.p.i + c.p.i = 0;

Syntax

class_definition :
   [ encapsulated ]
   [ partial ]
   ( class | model | record | block | connector | type |
     package | function )
   IDENT class_specifier

class_specifier :
   string_comment composition end IDENT
   | "=" base_prefix name [ array_subscripts ] [ class_modification ] comment
   | "=" enumeration "(" ( [enum_list] | ":" ) ")" comment

base_prefix :
   type_prefix

composition  :
   element_list
   { public element_list |
     protected element_list |
     equation_clause |
     algorithm_clause
   }
   [ external [ language_specification ]
              [ external_function_call ] [ annotation ";" ]
              [ annotation  ";" ] ]

element_list :
   { element ";" | annotation  ";" }

element :
   import_clause |
   extends_clause |
   [ final ]
   [ inner | outer ]
   ( ( class_definition | component_clause) |
     replaceable ( class_definition | component_clause)
        [constraining_clause comment])

component_clause:
   type_prefix type_specifier [ array_subscripts ] component_list

type_prefix :
   [ flow | stream ]
   [ discrete | parameter | constant ] [ input | output ]

Description

The flow prefix is used in order to generate equations for through variables, which sum up to zero in connections, whereas variables without the flow prefix are identical in a connection.