Encyclopaedia Index

- running executables
- compiling source code
- building executables

------------- PIL real; group 13 --------------- BFCA

BFCA... is used to carry the density of the incoming fluid at the boundary of a BFC case into the subroutine GXBFC. In a two phase case it represents the (phase 1 density) * (volume fraction) product at the inlet. The corresponding phase 2 value is carried by RSG28.

If DEN1 (and DEN2 for two phase cases) is STOREd, then inlet densities for individual patches can be specified by INIT statements for DEN1 (or DEN2).

For further information see the help and encyclopaedia entries on BODY-F and BFC, and GREX3 and GXBFC for further information.

(see BFC logical, Group 6)

---- PIL real; default=1.E30; group 25 -- -

BGCHCK....upper limit for F-array element INCHCK.

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BI[G]

Produces plots which, when reduced by 70% on a photocopier, will fit directly into a CHAM half-page report box. Default text uses size 2 characters. This is the default plot size. See also HELP on : FULL, LITTLE, PAGE

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BL[B]n [i] [j]

Plots data elements i - j using blobs of type n. If i & j are omitted, all elements in memory but not on the screen will be plotted. 'n' is an integer in the range 1 - 5, as follows:

BLB1 = circle;

BLB2 = square;

BLB3 = diamond;

BLB4 = '+';

BLB5 = 'x'.

If n is omitted, 1 is assumed

See also HELP on : PLOT,
DOT

How these are used is described by comments in the open-source Fortran file GXBLIN.HTM.

Both 'log-law' and 'power-law' velocity profiles can be set; and profiles are also provided for k, the kinetic energy of turbulence and eps, the volumetric dissipation rate of k.

Input-File-Library case v163 exemplifies the use of a 'BLIN' patch.

How to introduce such a patch *via* the VR-Editor is explained in
TR326 ,

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BL[OB] [i] [j]

Plots data elements i - j with circles at the data points. If i & j are omitted, all elements in memory but not on the screen will be plotted. Synonymous with BLB1. See also HELP on : PLOT, DOT, BLB

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BL[ock]....defines blocked regions for the plot, in which no contours or vectors will be plotted. PHOTON prompts for the number of blocked regions, and for the extent of the region in the X,Y and Z directions. Up to 10 blocked regions may be specified, and subsequent use of the block command will clear all previously defined regions.

A BLOCKAGE object defines a volume of material, either solid or fluid. For solid blockages, materials and heat sources can be specified. For fluid blockages, momentum sources can also be set. See the description in the PHOENICS_VR Reference Guide, TR326

(see POROSITY)

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BLOK....to employ the arbitrarily-adjustable block-correction feature of the equation solver, set STORE(BLOK) in the Q1 file. Values ascribed to BLOK indicate which cells are to be associated with which block. Set FIINIT(BLOK)=1.0 and INIADD=F; blocks then defined by PATCH/INIT commands should be given consecutive integer values.

The marker BLOK should be used to identify sections of the solution domain where the values of any solved-for variable (or the coefficients in the finite-volume equations) are expected to differ greatly from elsewhere in the domain. For example, in a conjugate heat-transfer problem, it would be appropriate to identify each solid component as a separate block.

The block-corrections, made for a selected variable every ISOLBK iterations, cause large-scale influences on the values of the variable solved in this way to be more rapidly transmitted to all parts of the domain, by grouping the cells in each block together as if to form a coarser grid. In this way, the speed of convergence may be improved for certain types of problem, particularly those in which different areas of the domain may have widely differing material properties.

Use of this feature requires IVARBK to be set equal to the index of the variable which is to be solved by the block-correction method, or to -1 when it is to be used for all variables.

The nature of the block-correction feature is this:

- If the number of blocks created is NBLOK, it solves NBLOK simultaneous linear algebraic equations by a direct matrix-inversion method.
- The NBLOK unknowns in these equations are the values of the corrections which, if applied uniformly to all cells in the individual block of cells, would make the nett residuals for the blocks zero.
- The coefficients in the NBLOK equations are derived from the equations for the individual cells by summation, in which process the cell-to-cell links within the block cancel each other out.
- Calls to the block-correction feature and to the standard cell-wise solver are interspersed within the main iteration loop.
- The corrections are applied as soon as they have been calculated, and the individual residuals of the cells within them are then re-calculated.

See also the entry on ISOLBK.

The block-correction feature is illustrated in library cases 100 and 459 to 467.

--- Command; defaults F; group 1 --- -

BOOLEAN....command to declare up to 50 PIL logical variables. For example: BOOLEAN(LOG1,LOG2,LOG3,LOG4) makes LOG1, LOG2, LOG3 and LOG4 recognised as local working logical variables. Any name of not more than 6 characters can be used, eg: BOOLEAN(LOGVAR).

Variables are assigned by the statement: LOG1= <logical expression>

Permitted simple logical expressions are:- T or F for TRUE or FALSE <logical variables> <numeric expression><operator><numeric expression> where implicit FLOATING is performed on Integer values and all FORTRAN operators are valid.

Simple logical expressions can be combined with the logical operators .AND. , .OR. , and .NOT. to create arbitarily complex logical expressions. There are two limitations:

- There is no precedence defined; and, in the absence of brackets, evaluation is carried out from left to right. It is therefore recommended that brackets are used to remove potential ambiguity from complex logical expressions.
- A .NOT. operator must not immediately follow an .AND. or .OR. without an intervening bracket. eg CARTES.OR..NOT.NONORT is illegal and must be re-written as CARTES.OR.(.NOT.NONORT)

In interactive work, the current set of user-declared logical variables, and the values assigned to them, may be displayed by entering the command SEE L.

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.

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BO[X]

Alternately removes and replaces the outer frame around the plot Default ON. See also HELP on : FRAME

(see CINT real array, Group 10)

----------- PIL real; group 13 -----------

BUOYA... is used by GXBUOY to carry the gravitational acceleration in the x-direction.

In the GRND4 (or LINBC) option for GRAVitational source terms, BUOYC is used as a constant in a linear function of two variables for the VALue.

See the help on GRAV for further information.

See PHENC entry: GRAVITATIONal sources

----------- PIL real; group 13 -----------

BUOYB... is used by GXBUOY to carry the gravitational acceleration in the y-direction.

In the GRND4 ( or LINBC) option for GRAVitational source terms BUOYC is used as a constant in a linear function of two variables for the VALue.

See the help on GRAV for further information.

----------- PIL real; group 13 -----------

BUOYC... is used by GXBUOY to carry the gravitational acceleration in the z-direction.

In the GRND4 (or LINBC) option for GRAVitational source terms BUOYC is used as a constant in a linear function of two variables for the VALue.

See the help on GRAV for further information.

----------- PIL real; group 13 -----------

BUOYD... is used by GXBUOY in the calculation of buoyancy forces to carry either;

- reference density for the GRND2 (or DENSDIFF) option
- volumetric expansion coefficient for the GRND3 (or BOUSS) option

See help on GRAV for further information.

----------- PIL real; group 13 -----------

BUOYE... is used by GXBUOY to carry the reference temperature in the GRND3 (or BOUSS) option for the calculation of buoyancy forces.

See help on GRAV for further information.

------ PIL real; default=0.0; group 19 ----

BZW1....is a 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), BZW1 is the radius of the crank.

If AZW1=GRND1, BZW1 is the constant piston velocity.