Encyclopaedia Index

CFD: Computational Fluid Dynamics

Chemical Vapour Deposition




Continuously-Varying Attributes (CVA, for MFM)

COSP, the inverse-problem solver

CUTC CVA, i.e. Continuously-Varying Attributes
CVD, i.e. Chemical Vapor Deposition CVM CYCLIC CYLINDR CZW1


----------------------------------------- -

Integer flags; value=16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50,...148, 150 but no match with C133, C150.

C1, C3, C5, C7, C9, C11, C13, C15, C17, C19, C21, C23, C25, C27, C29, C31, C33, C35, C37, C39,...C133, C135 standard names used to denote first-phase concentration full-field variables.


  1. On GRDLOC, C1 -> C50 only are defined.


  2. No pre-defined integer flag

See PHI and NAME for further information.


----------------------------------------- -

Integer flags; value=17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47, 49

C2, C4, C6, C8, C10, C12, C14, C16, C18, C20, C22, C24, C26, C28, C30, C32, C34....standard names used to denote second-phase concentration full-field variables.

See PHI and NAME for further information.


-------------- Advanced PIL command --- -

CALLs a PIL subroutine. See the HELP entry on SUBROUTINE for further information.


(Stream Set Menu)------------------------------------- Photon Help ----

[Cancel] will abandon the current streamline setting and return to the STREAMLINES menu.


(View Menu)------------------------------------ Photon Help ----

Undo changes in the current View-menu session.


------------------------------------- Photon Help ----

Ignore the [Quit] command and continue the current PHOTON session. Pressing any other menu button apart from [Exit] will have virtually the same effect.

See also: [Exit]


The forces on all solid BLOCKAGE objects are calculated if CALFOR=T is found in the Q1. This setting can also be made from the Output panel of the VR-Editor Main Menu. The default setting is F (or Off).

For further details of what printout is provided please see the entry in TR326.


is a PIL logical variable, used in conjunction with the solid-stress-simulation option (STRA = T).

Setting CALSTR = T activates the post-processing calculation of the stresses and strains from the displacements.


---- Logical; default=T; group 3 ---- -

CARTES....the default, T, signifies that rectangular Cartesian coordinates are to be used.

It should be set to F, for cylindrical-polar coordinates, in which case:

If the variable BFC is set T, CARTES has no significance, because body-fitted coordinates will be used instead.

Cartesian coordinates,displaying values of

(see SEEPTS command)

Cartesian coordinates,specifying rectangular

(see CARTES logical, Group 3)

Cartesian grids, definition of

A cartesian grid is composed of cells formed by the intersection of three sets of mutually perpendicular parallel planes, on any one of which either x, y or z is a constant, these quantities being the distances in the three coordinate directions. The spacings between the planes can be arbitrary functions of those distances.


CCM is an acronym for Co-located Co-variant Method; and it is also a PIL command used for activating that method.

See the PHENC entry Multi-Block grids and fine-grid embedding, for a full explanation.


CCV was formerly (i.e. prior to PHOENICS version 2006) a PIL variable which, when set to 'true' in the input file Q1, activated a solution algorithm for cell-centered rather than 'staggered' velocities.

This option was withdrawn when version 2006 was launched, because PHOENICS possesses two other similar options namely: CCM and GCV.

CDS, Central-differencing scheme

(see Schemes for convection discretization)


------ Real flag; value=1.0; group 13 - -

CELL....is a PATCH type denoting that the sources set by the associated COVAL's in group 13 are 'per cell', not per unit area, volume, etc.


A CELLTYPE object is used to define the location of one or more PATCH commands, together with their COVALs. The action of the PATCH/COVAL settings is restricted to the cells which fall inside the scope of the object. This object type never affects the grid, so createws no regions. See the description in the PHOENICS_VR Reference Guide, TR326


(Grid Menu)------------------------------------- Photon Help ----

[Centre] causes a grid to be plotted at the cell centre, rather than at the cell face. This may be useful when it is necessary to plot contours or vectors directly onto a grid, rather than in the space between two grids, as happens with the normal GRID setting. Clicking the cursor on this button will activate/deactivate the option.

CFD: i.e. Computational Fluid Dynamics

CFD is:
  1. The scientific body of knowledge which PHOENICS enbodies and uses in order to make simulations of fluid-flow, heat-flow and stresses-in solids phenomena.
  2. Click here for an introduction to CFD.
  3. Also called Colourful Fluid Dynamics because of its practitioners are thought sometimes to use attractive colour images to distract attention from the doubtfulness of its predictions.
  4. Also Cheats, Frauds and Deceivers by those who blame its promoters for the fact that some of its users believe too credulously, and to their disadvantage, in its predictions.
  5. Click here for a power-point presentation which discusses to what extent CFD predictions can be trusted.


------------------------------------- Photon Help ----

[Centre] toggles the vector-plotting mode. Two modes are available, with vectors being plotted either radiating from cell centres (Yes) or centred about the cell centre (No). The default is to plot vectors radiating from cell centres (No).

Centred Grids

Grids are plotted at cell boundaries, whereas contours and vectors are plotted at cell centres. The GRID CENTRE command in PHOTON permits plotting the grid in the same plane as vectors and contours. The format of this command is:

GRID CENTRE <plane> <number> <subregion> <options>

for which the parameters are the same as those of the GRID command.

Cell-centred grid outlines and hatches may also be plotted by means of GRID OUT CENTRE and GRID HATCH CENTRE commands.


----- Real; default= 0.0; group 10, s -

CFIPA....parameter used in reference-interphase-friction formulae.

(see CFIPS)


----- Real; default= 0.0; group 10, s -

CFIPB....parameter used in reference-interphase-friction formulae.

(see CFIPS)


----- Real; default= 0.0; group 10, s -

CFIPC....parameter used in reference-interphase-friction formulae.

(see CFIPS)


----- Real; default= 0.0; group 10, -

CFIPD....parameter used in reference-interphase-friction formulae.

(see CFIPS)


-------- Character*4 array; dflt=' '; -

CG....is an array for transferring to GROUND any special character data that the user may need there.


------------ Command; group 1 --------- -

CHAR....command to declare up to 50 PIL variables of 'character' type.
For example:
makes CH1, CH2, CH3 and CH4 recognised as local working variables.

The name of the character variable may be of any length; but only the first eight characters are significant.
Thus, FLUID_NAME will be treated as FLUID_NA

The values of the variables may be up to 68 characters long; thus:
is well within the limit.

Variables are assigned by the statement:
CH1 = [character expression]

Permitted character expressions are:-

Note that to assign the string stored in one character variable (or array element) to another, the name of the variable must be enclosed by colons:
simply setting CH2 = CH1 will assign the string CH1 to CH2, not the string stored in CH1.

The Satellite will convert character strings to upper-case; but, should users want to keep character strings case-sensitive, they must place them within apostrophes.
For example, the following two character variables will contain different strings:

CH1 will contain Hello! and CH2 will contain HELLO!

Another method of assigning a value to a character variable is the "table method", by which one can assign up to four strings to a character variable in a table format.
For example, if the following PIL line is issued:
CH1 = 'ASDF',1,'GG',10,'XXXXXX',35
then CH1 will contain the following expression:

ASDF     GG                       XXXXXX

In other words:

When the Satellite is run interactively, the current set of user-declared character variables, and the values assigned to them, may be displayed by issuing the command:

The default provision of up to 50 variables can be enlarged by re- dimensioning in the MAIN program of the SATELLITE.
See DIMENS for further information.


command (see GROUP 1)

Chen-Kim KE-EP Turbulence model

See PHENC entry: The Chen-Kim modified KE-EP turbulence Model


------------ Advanced PIL command --- -



If FUNC is F on entry, the length of variable is checked against LEN.

If it is greater than LEN, LEN is reset to the actual length, and FUNC is reset to T.

If FUNC is T on entry, variable is truncated to LEN.


------------ Advanced PIL command --- -


The command checks whether VARIABLE is a valid PIL,REAL,INTEGER, LOGICAL or CHARACTER variable, as specified by TYPE. TYPE may also be ANY to check if VARIABLE exists at all.

LOG, which can be any valid PIL logical variable, is set T if the condition is satisfied, and F if it is not. For the types REAL and INTEGER, VARIABLE may also be a number or an expression enclosed in colons(:). LOG will be set T if the number or expression can be evaluated correctly according to TYPE.


----------- Real; group 13 ----------- -

CHSOA... is a constant used by gxchemso in the calculation of the chemical source terms.


----------- Real; group 13 ----------- -

CHSOB... is a constant used by gxchemso in the calculation of the chemical source terms.


----------- Real; group 13 ----------- -

CHSOC... is a constant used by gxchemso in the calculation of the chemical source terms.


----------- Real; group 13 ----------- -

CHSOD... is a constant used by gxchemso in the calculation of the chemical source terms.


----------- Real; group 13 ----------- -

CHSOE... is a constant used by gxchemso in the calculation of the chemical source terms.


---- Real; default= 0.0; group 10, s -

CINH1A....parameter used in formulae for phase-1-to-interface transfer-coefficient formulae. Further parameters of the same kind are CINH1B and CINH1C. See CINT.


---- Real; default= 0.0; group 10, s -

CINH2A....parameter used in formulae for phase-2-to-interface transfer-coefficient formulae. Further parameters of the same kind are CINH2B and CINH2C. See CINT.


(Geometry Menu)------------------------------------ Photon Help ----

[Circle] draws a closed circle by typing in three points in the input window.


A CLIPPING_PLANE object is used to graphically clip the screen image. It has no effect on the solution. See the description in the PHOENICS_VR Reference Guide, TR326


CLR is a PIL command which may be issued during an interactive session, or inserted in a Q1 file.

Its effect is to clear the screen.

Library case 374 illustrates its use for introducing a new 'display' sequence after another library case has just been loaded.


is a PIL variable:
Real; default= 0.0; group 10 -

CMDOT....interphase mass-transfer parameter for ONEPHS=F.

The mass-transfer rate ( positive from phase 2 to phase 1 ) is equal to
where FIP is the reference inter-phase transfer coefficient determined by the setting of CFIPS.

If CMDOT equals GRND, EARTH visits SECTION 2 of GROUP 10 of GROUND.HTM for a user-supplied value of the interphase-mass-transfer rate for each cell at the current IZ slab. This EARTH array of values is addressed in GROUND by means of the integer flag INTMDT.

If CMDOT is set equal to GRND1, GRND2, .....GRND9, built-in coding is used instead, This is to be found in the open-source file GXIMAS.HTM, where the options are:-

If CMDOT is set to HEATBL, however, the rate of interphase mass transfer is computed from the balance of heat transfer to the interface from both phases, according to the following expression:

         ( COI1*(H1-PHINT(H1)) + COI2*(H2-PHINT(H2)) + S )
                 ( PHINT(H1) - PHINT(H2) )  

In this expression,

  1. the denominator is the latent heat of vaporization;

  2. COI1 is the transfer coefficient for enthalpy from the bulk of phase 1 to its interface with phase 2,

  3. COI2 is the transfer coefficient from the bulk of phase 2 to its interface with phase 1, and

  4. S denotes the sensible heat transfer from bulk to interface supplied by the material approaching the interface,
    This is equal to:

CMDOT=HEATBL is often used for steam and water systems where evaporation and condensation occur at the steam-water interface.


----- Real; default= 0.0; group 10, s -

CMDTA....parameter used in interphase-mass-transfer formulae. Further parameters of the same kind are: CMDTB,CMDTC,CMDTD,CMDOT


is an integer, equal to 2, which is used to indicate that the first-phase compressibility [= d(ln rho1)/dp] is to be selected in GROUND subroutines such as gxprutil.htm.


is an integer, equal to 4, which is used to indicate that the second-phase compressibility [= d(ln rho2)/dp] is to be selected in GROUND subroutines such as gxprutil.htm.


CO is an integer index, used in GROUND. It refers to the storage location of the 'coefficient' array, and is used to set the coefficients of linearised-source expressions.


------------------------------- -

The third argument of the COVAL command is known as the COefficient. It is in essence the constant of proportionality connecting the source to be set by COVAL with the excess of the nodal value of the variable in question ( indicated by the second argument of COVAL ) over the fourth argument of COVAL ( known as the VALue ).

Any numerical magnitude can be entered for a COefficient, but some have special significances. These are provided with names which are recognised in PIL. Their names and magnitudes ( in brackets ) are:
FIXFLU(2.E-10) FIXVAL(2.E10) FIXP(1.0)
OPPVAL(-10250.0) ONLYMS(0.0) ZERO(0.0)
GRND(-10110.0) GRND1(-10120.0) GRND2(-10130.0)
GRND3(-10140.0) GRND4(-10150.0) GRND5(-10160.0)
GRND6(-10170.0) GRND7(-10180.0) GRND8(-10190.0)
GRND9(-10200.0) GRND10(-10210.0)  

See COVAL for further information.


COI1 is an integer index, used in GROUND. It refers to the storage location of the inter-phase-transfer coefficient from phase 1 to the interface.


COI2 is an integer index, used in GROUND. It refers to the storage location of the inter-phase transfer coefficient from phase 2 to the interface.

The COLDAT file

This file resides in \phoenics\d_allpro and may be seen by clicking here. It contains data specifying the colours to be used in PHOTON and SATELLITE menus.

Users who wish to use other colours than those in the above file should replace the line: COLDAT=\phoenics\d_allpro\coldat in their private PREFIX file by a similar line which indicates where the desired coldat is to be found.

Convection fluxes for cartesian co-located velocities balances in BFCs

In present implementation of non- staggered algorithm U1, V1 and W1 will still be solved for; but the values of these quantities will be over- written, just after they have been solved by PHOENICS, with values which have been obtained from the cell- face velocity interpolation formulae.

At this point, these are the convection fluxes for cartesian co-located velocities balances in BFCs that deserve special attention. Two practices are employed to calculate the mass fluxes from cell-face values of cartesian velocities on general non-orthogonal curvilinear grids. The first is used when NONORT=T and second is, at present, recommended for general use followed by NONORT=F, which is default value. The distinction between them will now be discussed in brief.

When NONORT=T the cell-face cartesian velocities are transformed to velocity resolutes aligned with local direction of the grid and replace U1, V1 and W1 to provide the mass flux calculations by EARTH procedure taking into account the contributions from non in-face resolutes.

In contrast, if NONORT is set F, U1, V1 and W1 are over-written by values of mass fluxes directly calculated from cell-face cartesian velocities and surface areas of the cell faces. Then the area projections used by EARTH in the formulae for mass fluxes are removed. The advantage of this practice is the exact mass flux calculations for the grids with significant departures from orthogonality without any need for special treatments like NONORT=T option.

The four new low dispersion convective schemes with local oscillation- damping facilities have been implemented by introducing the additional source terms to provide for the differences between the desired formulation and the UDS one. So, the whole set of the convective schemes available for non-staggered calculations now includes seven formulations.


Relevant links

COMBUStion processes can be represented by PHOENICS if suitable settings are made of thermodynamic and transport properties (see PROPERTIES) and reaction-rate sources (see REACTION-RATE). Radiative effects can also be modelled if required: see RADIATION for details.

GREX contains the simple-chemical-reaction scheme (SCRS) model in which fuel and oxidant are presumed to combine in a single step to form a product, viz.

FUEL + OXIDant ------> PRODuct

Two options are provided, namely:

  1. the mixing-controlled reaction-rate option; and,
  2. the kinetically-controlled reaction-rate option.

The PIL settings common to both options are:

    CHSOA= MIXture Fraction (mass fraction of fuel whether burned or
             not) at which stoichiometric conditions prevail.
    TMP2B= the heat of reaction of the fuel.
    CP1 = GRND10
    CP1A= the specific heat of the fuel.
    CP1B= the specific heat of the product.
    CP1C= the specific heat of the oxidant.
    RHO1A= the molecular weight of the fuel.
    RHO1B= the molecular weight of the oxidant.
    RHO1C= the molecular weight of the product.

The two options are distinguished from one another by the following settings:

for option (a)...STORE(FUEL);TMP1=GRND7;
for option (b)...SOLVE(FUEL);TMP1=GRND8 and in addition one of the
reaction-rate sources ( see REACT ) must be selected.

Library case 492 exemplifies the use of the SCRS model.


See PHOENICS Commander


(Vector Edit Menu)---------------------------------- Photon Help ----

[Component] specifies the three components of the vectors. " - " can be used to set a particular component to zero.

Composite-flux model,activating the

(see RADIATion command, Group 7)

Compressibility of phase-1 fluid

(see DRH1DP real, Group 9)

Compressibility of phase-2 fluid

(see DRH2DP real, Group 9)

Compressible gas flows, convergence in

Convergence is sometimes difficult to achieve for high-Mach-number flows when, as has often been the practice in the past, the temperature has been deduced by subtracting the kinetic energy of the time-mean motion from the stagnation enthalpy. The recommended practice is to interpret H1 as the specific enthalpy of phase 1, not its stagnation enthalpy, and to activate (or rather not deactivate) the built-in source terms for this variable, which represent:

Computations which proceed in this way converge much more smoothly than those proceeding by way of stagnation enthalpy; and, in most cases they lead to identical results. In just one respect, however, they may be deficient: when strong shocks appear in the flow, the built-in calculation of the viscous dissipation term may be an underestimate, because it cannot calculate correctly the velocity gradients in the shocks. In these circumstances, ad hoc additions may be needed, the magnitudes of which can be calculated from well-known thermodynamic relations.


are created when, in the cham.ini file , the following line appears:
compress = on

PHI file so compressed are usually less than half the size of the uncompressed file.

The compression is handled within EARTH; and both PHOTON and the VR Viewer can read such files.

There also exist stand-alone compression and de-compression utilities, which can be applied to individual files.

Computational domain

The portion of physical space in which the problem is solved.


CON1E,CON1N,CON1H,CON2E,CON2N,CON2H are the block-location indices of the convection fluxes (i.e. the mass flow rates) across the east, north and high cell faces, for the first and second phases respectively. They are stored in blocks of length NX*NY*NZ in the F-array.

Therefore the value of CON?? for the cell characterised by the indices IX, IY and IZ can be accessed as:

F(L0f(con??) + IY + NY*(IX-1) + NX*NY*(IZ-1))

CONFIGuration files

CONFIGuration files are those which are read by the various PHOENICS executable modules for information on the locations and natures of the files which must be accessed during execution.

There is a CONFIGuration file for each PHOENICS program, residing in the relevant directory, as follows:

SATCON in d_satell,
MENCON in d_satell,
EARCON in d_earth,
PHOCON in d_photon,
AUTCON in d_photon,
PINCON in d_utils

In addition a file called CONFIG, which is common to all programs, resides in d_allpro.

Users are advised not to modify these files in any way.


---------------------------------- C Photon Help ----

Confirm the range of [DELETE], [OFF] or [ON].

Conjugate-Gradient Solvers in PHOENICS

Three versions of conjugate-gradient solver are available, as follows:

nameCSG3 valueNotes
conjugate gradient'CNGR'recommended
conjugate residual; classical pre-conditioned'CGGR'Suitable for solving for pressure and velocities
congugate residual;explicit residual'CRGR'Suitable for any variable

The first can be activated for all variables by setting CSG3='CNGR' in the Q1 file; or it can be activated for individual variables by the appropriate setting of ENDIT

To call either of the last two solvers, the user should set USOLVE = T and choose the name of the solver by appropriate setting of CSG3 variable in Q1 file:

Relevant Fortran coding is to be found in the open-source file GREX3.HTM.

The Fortran of the three solvers themselves is in the closed part of EARTH.

See also PHENC entry icngra/b/c


a means of activating CONWIZ, the convergence wizard can be activated by loading into the q1 file a PIL macro called 'conprom' (an abbreviation of 'convergence-promoter'). This is done by inserting the line:


into the Q1 file.

how this works is explained here.

CONTACT resistances

The Group 12 feature allowing diffusion coefficients to be modified patchwise has been extended to allow the addition of resistances to heat transfer brought about by the inclusion of thin (sub-grid-scale) sheets of poorly-conducting material.

For more information: see the Encyclopaedia entry 'PATCH'.

Continuity imbalances of phase 1

(see IMB1 integer name, Group 7)

Continuity imbalances of phase 2

(see IMB2 integer name, Group 7)


---- Real flag; value=25.0; group 23 -

CONTUR....is a PATCH-type specification which indicates that one or more contours are to be plotted, at field-print-out time, for the PATCH in question.

The numbers of columns and rows to be occupied by the contour plot are dictated by the values given to the variable NCOLCO and NROWCO respectively; their default values are 45 and 20. ICHR controls whether odd, even or both-value bands are filled with characters.

See PATCH and TYPE for further information.

CONTUR plots, setting columns for

(see NCOLCO)

Convection and diffusion adjustments

(see GROUP 12)

Convection fluxes, accessing and altering

(see UCONV)

Convection neighbours, accessing or altering

(see UCONNE)

Convection schemes

(see Schemes for Convection discretization)


a PIL variable of boolean type, default = F, which activates the PHOENICS 'convergence wizard'. It is currently effective only for structured-grid PHOENICS.

Copy grid meshes

(see GSET(C,...) command, Group 6)

COPYQ1 file

All syntactically-valid data-setting commands and comments (ie command categories 1,2 and 6), read from the Q1 file or supplied during the interactive session, are written to the file COPYQ1.

Thus, if the computer system 'crashes' during a 'TALK' session, the entries already made are not lost.


---- Real; default= 0.0 ; group 13 -

CORIOL....when set to a value other than zero, causes momentum sources per unit mass which are equal to CORIOL*V1 for U1, -CORIOL*U1 for V1, and to corresponding expressions for the second-phase velocities. This facility is useful for representing Coriolis forces in horizontal flows, for example atmospheric or hydrospheric simulations.

The value of CORIOL is equal to twice the angular velocity of the rotating co-ordinate system.

For the surface of the Earth, therefore, CORIOL equals 1.4544E-04 times the sine of the latitutude, being therefore zero at the equator and having a maximum at the North Pole and a minimum at the South Pole.

Corner coordinates, setting of

(see SETLIN and SETPT commands, Group 6)

The following statement in GREX3 arranges for the print-out of corner coordinates when STORE(XCEN,YCEN,ZCEN) appears in the Q1 file:

     1       LBNAME('ZCEN').NE.0 

Correction coefficients, accessing and altering

(see UCORCO logical, Group 8)

Correction values, accessing and altering

(see UCORR logical, Group 8)

Courant limit

The Courant limit is the width of the cell divided by the velocity through it; and it is often so small that a very large number of time steps must be computed for a flow simulation of practical interest, which sometimes entails unacceptably large computing charges.

PHOENICS, because of its fully-implicit formulation of the finite-volume equations, can take time steps which exceed the Courant limit by many orders of magnitude; and it is then that under relaxation may be required in order to ensure smooth convergence of the iterative procedure.


----- Real; default= 4.182e3; group 9 -

CP2....is like CP1, but for the second phase. It is set in Group 9, Section 15 of GROUND.

The default value is that of water at standard pressure and temperature. The GRND10 option is not active for CP2.

If STORE(CP2) or STORE(SPH2) appears in Q1, then the specific heat will be placed in a 3D store and will be available for printing in RESULT and plotting with PHOTON from PHI.

In GROUND, the integer index ISPH2 should be used in calls to FN routines or as the argument of L0F.


a PIL variable of character type, default = ' ', which determines what special menu is required.

Click here for more information


CREK is the name used for a collection of subroutines forming part of the advanced-chemical-reaction option of PHOENICS.

Their function is to calculate the chemical composition and temperature of a chemically-reacting gas mixture, whether the reaction is in equilibrium or is kinetically controlled.

CREK consists of one open FORTRAN-77 subroutine, namely GXCREK, which is called, in the only exemplification supplied with Phoenics 3.2, from the subroutine GXNOX, which is called from GREX3. It resides in the file GXCHEM.F

The calling program seeks solution for values at a point P of mole numbers of chemical species, (S2(i),i=1,ns) and the temperature TK, given the values of the same variables at neighbouring nodes, and values at P at a previous time step or estimates from a previous iteration.

The calling program must first express the species- and energy- conservation in the standard finite-volume equations form:

AP*S2(I),P = AE*S2(I),E + AW*S2(I),W + AN*S2(I),N + AS*S2(I),S +AH*S2(I),H + AL*S2(I),L + SO(S2(I)) , I=1,NS


       AP = AE + AW + AN + AS + AH + AL + AP,M
       AD denotes convective and diffusive flux coefficients
          at neighboring nodes D = e,w,n,s,h and l, kg/cu m-sec
       AP,M is influence term from P at previous time step
       S2(i) is the mole no. of species i at point P, kg-mols i/kg
       S2(i),D is the mole no. of species i at near-node D,
               kg-mols i/kg
       SO(S2(i)) is rate of appearance of species i due to chemical
               reaction, kg-moles i/cu m-sec

AP*H,P = AE*H,E + AW*H,W + AN*H,N + AS*H,S + AH*H,H + AL*H,L + SO(H)


H,P is the mixture enthalpy at point P, J/KG H,D is the mixture enthalpy at neighbor nodes D, SO(H) is rate of heat addition to control volume by radiative and kinetic heating, J/CU M-SEC

The calling program must supply the following variables through the labelled COMMON BLOCK /CPARAM/

TK = temperature at node P, degrees Kelvin (estimate)
PA = pressure at point P, Pascals (nt/sq m)
S1(I) = (AE*S2(I),E+AW*S2(I),W..+AL*S2(I),L) / AP S2(I) = previous solutions or estimates for s2(i)...

* if temp TK is set to zero, program constructs *** own estimates *** HSUB0 = (AE*H,E+AW*H,W...+AL*H,L) / AP , J/KG * Q0,Q1,Q2,Q3,Q4, = coefficients in expression following... SO(H) = -(Q0+Q1*T+Q2*T**2+Q3*T**3+Q4*T**4) , J/CU M-SEC

LADIAB = T ---> ignores above expression for source(h), takes source(H)=0.0 LEQUIL = T ---> equilibrium solution sought = F ---> kinetic solution sought LREACT = T ---> chemical reaction permitted (eql or kin) = F ---> adiabatic non-reacting mixing LDEBUG = T ---> intermediate debug printing = F ---> no intermediate debug printing

S2(I),I=1,NS is the solution set of mole numbers, kg-moles i/kg TK is the temperature (degrees K) from thermal energy equation HSUB0 is static enthalpy at node point P (J/KG) RHOP is the mass density at node point P (KG/M**3) SM is reciprocal molecular weight (KG-MOLE/KG) ASUB(I,3) is the species name.

Dimensions NLM = number of elements (7) NS = number of chemical species (20) JJ = number of chemical reactions (36)

These dimensions may be adjusted by simply changing the following labelled common blocks:


and the following dimension statement in routine CALC.

Study of the examples in the advanced-chemistry option library reveals how CREK may be used.


------ Character*4; default=' '; -

CSG1,CSG2,....CSG10....are character variables provided for communication between the SATELLITE and GREX. Some examples of the use of these indices are to be found in subroutine GREX.


CSG3 is set on the Q1 file to select a linear-equation solver. Thus:

If no setting is made, the default "Stone-type" solver is activated.


CSG4 is used in connexion with the CHEMKIN interface for the naming of a file. See the description of this interface in section 2 of POLIS.


CSG10 is used to name the file, if other than PROP, from which material- property data are to be read if the relevant symbol (eg DEN1, CP1, etc) is set equal to GRND10 in the Q1 file.

CSG10='Q1 ' is appropriate if the data are supplied in the Q1 file below a line containing the word MATFLG(If props added in q1 they will not appear in the VR-Material-Scroll window)

CSV File Creation

The CSV ("Comma Separated Values" ) file format is often used to store tabular data in plain-text form. The file consists of any number of records separated by line breaks, and each record consists of an identical sequence of fields, which are separated with commas. Perhaps because they are used in Microsoft Excel, they have become a de facto industry standard for the tabular output of field variables.

CSV files are directly compatible with the AUTOPLOT table format.

They are used in PHOENICS as an export format to output the following:

  1. aerodynamic forces vs sweep or time step to a file named 'forces-*.csv', where * is the the first character of the name of the PHI/PHIDA solution file (see Forces exerted by fluids on solid objects);
  2. profile plots of field variables from the VR Viewer to a file named '<varname>_profile.csv', where <varname> is the name of the selected variable. (see Plot variable profile);
  3. the surface contour values of a selected VR object by writing a file named <objname>_<varname>.csv, where <objname> is the object name and <varname> the current variable name. (see VR-Viewer Object context menu);
  4. the profile values associated with the surface contour values of a selected VR object at a selected plane. The data are written to a file named <objname>_<varname>_<plane>_<planeloc>.csv, where <objname> is the object name, <varname> the current variable, <plane> the currently select plane (X,Y or Z) and <planeloc> the current position of that plane. (see VR-Viewer Object context menu);
  5. time history plots of a selected field variable if a Point_history object has been selected in the VR Viewer. The data points are automatically saved to the file with the default name <objname>_<varname>_history.csv where <objname> is the name of the object and <varname> is the name of the selected variable. (see The Object Dialog Box)

The In-Form facility can be used to produce bespoke tabular output in CSV format to named files, as explained here: Tabular output to CSV file

CVM, the "Virtual-Mass" coefficient

See the Encyclopaedia article on virtual-mass momentum sources

Curve, setting of

(see GSET(V,...) command, Group 6)

Curvilinear grid, definition of

A curvilinear grid is best imagined by supposing that a regular cartesian grid is embedded in a jelly-like medium, which is then squeezed, stretched, bent and twisted in an arbitrary way. All the cells which were originally in contact with one another remain so; but their shapes may have changed considerably.

Curvilinear grids are so often used for flow simulations in which it is desired that the grid should conform to the curved surface of some body, that they are often called body-fitting coordinates, or BFC's for short. It is indeed under these headings (or rather BFC and BODY-F) that they appear in the Encyclopaedia.

Cylindrical-polar grid, definition of

A cylindrical-polar grid, in contrast to a cartesian grid, consists of cells formed by the intersection of:

In cylindrical coordinates, the location y=0 need not correspond to the axis. It is displaced from the axis by the radial extent RINNER (the default value of which is zero). Thus, for flow in an annulus, y=0 corresponds to the inner surface of the annulus.

Once again, the intervals of x, y and z may be arbitrarily chosen.


------ Real; default=0.0; group 19 ---- -

CZW1....parameter used in specification of the movement of the first part of an n-part grid. In the piston-in-cylinder example provided in subroutine GXPIST ( called from GREX ), CZW1 is the ratio of the length of the connecting rod to the crank radius.

See also IZW1, AZW1 and BZW1.