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The Variables Section

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The Variables Section

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The VARIABLES section is used to define and assign names to all the primary dependent variables used in a problem descriptor.  The form of this section is

VARIABLES        variable_name_1 , variable_name_2 ,...

All names appearing in the VARIABLES section will be represented by a finite element approximation over the problem mesh.  Each variable is assumed to define a continuous field over the problem domain.  It is further assumed that each variable will be accompanied by a partial differential equation listed in the EQUATIONS section.

Each variable_name may be followed by various qualifiers, which will be described in subsequent sections.  These qualifiers allow you to control mesh motion, declare complex and vector variables, declare arrays of variables, and control some of the ways FlexPDE treats the variable.

In assigning names to the dependent variables, the following rules apply:

Variable names must begin with an alphabetic character.   They may not begin with a number or symbol.
Variable names may be a single character other than the single character "t", which is reserved for the time variable.
Variable names may be of any length and any combination of characters, numbers and/or symbols other than reserved words.
Variable names may not contain any separators.  Compound names can be formed with the '_' symbol (e.g. temperature_celsius).
Variable names may not contain the character '-' which is reserved for the minus sign.

Example:

VARIABLES
 U,V