Encyclopaedia Index

Full-field variables

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Full-field variables

(a) Definition
(b) Dependent variables (DVs)
(c) Auxiliary variables
(d) Special auxiliary variables ( SAV's)
(e) Material properties:
(f) Whole-field-solver variables (WSVs)

(a) Definition

FFV's are those variables which have a stored value for each cell of the grid. There are therefore NX*NY*NZ values stored for each variab of a given kind. It is immaterial, as far as the PHOENICS user is concerned, whether the values happen to be stored in core memory or on disc.

One group of FFV's comprises the variables for which storage is allocated as a consequence of the STORE, SOLVE or SOLUTN commands in the SATELLITE, such as:

SOLVE(P1,U1,V1,H1,ABCD) or

Another group of FFV's are those associated with the whole-field solver.

(b) Dependent variables (DVs)

Full-field variables may be, but need not be, the dependent variable (DV's) of conservation equations, such as pressure, velocity, enthal or concentration, ie those for which Y appears as the third argument of SOLUTN in the Q1 file.

These may be regular PHOENICS variables, such as pressure (P1), firs phase x-direction velocity (U1) and second-phase enthalpy (H2); or they may be variables to which users wish to ascribe a significance of their own, as for example the ABCD in (a) above.

The complete list of the integer names of regular variables is contained in the first COMMON block of the file GRDLOC,thus:

COMMON/LBFFV/P1,P2,U1,U2,V1,V2,W1,W2,R1,R2,RS,KE,EP,H1,H2, 1C1,C2,C3,C4,C5,C6,C7,C8,C9,C10,C11,C12,C13,C14,C15,C16,C17, 1C18,C19,C20,C21,C22,C23,C24,C25,C26,C27,C28,C29,C30,C31,C32, 1C33,C34,C35

The complete GRDLOC file may be inspected via POLIS (path 1/4/..).

In an unsteady-flow problem, the values of dependent variables which pertain to the PREVIOUS time step, ie the so- called "old" values, are also FFV's. Storage is automatically provided for these variables whenever:-

(i) A SOLVE or SOLUTN command has required that the variable in question shall be solved for; and

(ii) the variable STEADY has been set to FALSE; and

(iii) a Y appears as the fifth argument of the relevant TERMS command, either by direct setting or by default.

The command SOLVE(TEM1) may also be employed so as to activate the direct solution for temperature, as distinct from its indirect solution via enthalpy. The name TEM1 is recognised within PHOENICS as necessitating the activation of sequences for multiplying by the specific heat (see TEM1 for more details).

(c) Auxiliary variables

FFV's may also be auxiliary variables, which are STOREd but not SOLVEd, ie those for which N (no) appears as the third argument of SOLUTN, while Y (yes) appears as the second argument. Porosities are of this kind, as are those variables which users decide to introduce for their own purposes in GROUND. The above example of a STORE command creates storage for two such variables, namely HPOR and EFGH.

Auxiliary variables are not provided with field stores at the previous time step, because EARTH has no need for them.

(d) Special auxiliary variables ( SAV's)

Also to be numbered with the FFV's are those special auxiliary variables (SAVs), which may be given FFV status for purposes of print-out or under-relaxation, by the use of STORE(name). The complete list of names which may be used is as follows:

(e) Material properties:

        DEN1 or RHO1    for first-phase density;
        DEN2 or RHO2    for second-phase density;
        VISL or ENUL    for reference laminar viscosity;
        VIST or ENUT    for reference turbulent viscosity;
        TMP1            for first-phase temperature;
        TMP2            for second-phase temperature;
        LEN1 or EL1     for first-phase length scale;
        LEN2 or EL2     for second-phase length scale;
        INTMDT or MDOT
        or CMDOT        for interphase mass-transport from
                        phase 1 to phase 2;
        INTFRC or CFIP  for interphase friction.

(ii) Marker properties:

BLOK for the block-correction indicator;
PRPS for the material-property indicator.

(iii) Solution-related quantities:

PCOR for the pressure correction;
IMB1 for the first-phase mass or volume imbalances;
IMB2 for the second-phase mass or volume imbalances.

All the integer names of SAV's are to be found within COMMON /IDATA/ in the file SATEAR, which may be viewed via POLIS (path 1/4/...).

(f) Whole-field-solver variables (WSVs)

There is a further sub-class of FFV's which, because they are stored differently from those mentioned so far, require to be distinguished. These are the "whole-field-solver variables" (WSV's) which are employed when the whole- field solver is to be activated for a dependent variable.

The difference between the storage arrangements for the WSV's and the FFV's is that the former occupy segments of the F-array containing NX*NY*NZ contiguous locations; whereas the latter occupy NZ non-contiguous segments, each containing NX*NY locations. This matter will be further discussed below.

The complete list of the integer names of the WSV's, all of which appear in COMMON /LB/ of the file GRDLOC, is: