PHOENICS is designed to serve two kinds of user: those who wish to perform flow simulations of standard kinds, with standard fluids, and by standard methods; and those whose needs or intentions necessitate the addition, in GROUND-type subroutines, of special FORTRAN-coding sequences.
This entry is intended to assist users of the second kind, by explaining how they can create such coding sequences, and also by introducing some of the features which PHOENICS provides to make their task easier.
These explanations make reference to how PHOENICS stores its data in memory, in the so-called F-array; and, since different classes of variable are stored in different ways, nomenclature will be introduced which distinguishes these classes.
PHOENICS permits the user of GROUND subroutines not only to work with individual elements of its F-array, but also to manipulate whole segments of the array which contain variables of a defined class.
Special subroutines are provided for this purpose. Their use is described in the present chapter; and also explained is how users can create additional functions of their own, thereby increasing both the compactness and the economy of their coding.