Encyclopaedia Index

R1/2 RADIATIVE HEAT TRANSFER RADIA RADIAT RADIATION BOUNDARY CONDITIONS
RADIB RADIUS RANGE

REACTION-RATE

READ in PHOTON READCO READFI READQ1 REAL REALREAD READVDU

RECIPROCAL/X/Y REDRAW REFERENCE REFINE REFLIB REGEXT REGION
RELAX (the PIL variable) RELAXATION (the technique)
Relational Data Input
RELIABILITY of predictions RELXC/YC/ZC
Remote computing
REPLACE REPLAY
Reserved Names RESET RESFAC, the residuals factor RESIDUALS

RESREF RESTRT RESULT FILE REYNOLDS-stress turbulence model

RG ARRAY RG2D RGRAD RHO1/1A RHO2/2A RightHand/LeftHand System RINNER RLOLIM RLXU1/V1/W1 RNG-derived KE-EP turbulence model

ROSA

ROTATE_command_in_PHOTON ROTATIONAL_Momentum_Sources
ROTAXA/XB ROTAYA/YB ROTAZA/ZB
ROTOR object
ROUGHNESS wall functions ROWS

RQ1 RS RSET RSGx RSTGEO RSTM Ruled grids in AUTOPLOT

RUN Run titles and other preliminaries RUNAUT RUNEAR RUNPINTO RUNPIN RUNPHO RUNSAT RUNSTX

RUPLIM RV2D


R1

- -

Integer flag; value=9.

R1....standard name used to denote the first-phase volume fraction.

See PHI and NAME for further information.


R2

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

Integer flag; value=10.

R2....standard name used to denote the second-phase volume fraction.

See PHI and NAME for further information.


RADIA

-------- PIL real; groups 9 & 13 ---------

RADIA... is used to carry the radiation absorption coefficient in cases where the radiation model is activated.


RADIAT

RADIAT....is a PIL command which is used to activate either the composite-flux radiation model or the composite radiosity radiation model. These radiation models are coded in subroutine GXRADI, which is called from GREX3.

The syntax is:

RADIAT(Model,ABSORB,SCAT,Energy)

where:

The user is advised to employ absolute temperature in degrees K, although the of the PIL variable TEMP0 to define a reference temperature, eg TEMP0=273K is allowed.

The command:

RADIAT(Model,ABSORB,SCAT,Energy)

is equivalent to the following PIL settings:

The user is reminded that in earlier versions of PHOENICS the syntax of the RADIAT command was:

RADIAT(ABSORB,SCAT,CP)

This activated the composite-flux model; solution of the H1 equation; and set TMP1=GRND2 and TMP1B=1/CP.
This syntax is still supported in later versions, although TMP1 and TMP1B are no longer set.
Therefore, if H1 is solved the user must select the enthalpy-temperature option and associated specific heat separately;
or alternatively if TEM1 is solved, the user must set the specific heat via the PIL variable CP1.

>>> For more detailed documentation see the Encyclopaedia entry 'RADIATIVE HEAT TRANSFER IN PHOENICS'.


RADIATION and FREE-CONVECTION BOUNDARY CONDITIONS

The star-name-patch feature has a special effect when the variable appearing in the COVAL statement is TEM1, enabling it to represent radiative or free-convective heat loss to (or gain from) surroundings of different temperature.

The RADIATIVE-TRANSFER CASE is activated by following the * in the patch-name by RAD. Then the source introduced within EARTH, per unit area if an area type is chosen, is:

CO * ((VAL + TEMP0) ** 4 - (TEM1cell + TEMP0) ** 4)

where CO and VAL are the COVAL arguments.

Here TEMP0 is the PIL variable representing the quantity which must be added to the temperature on the prevailing scale to make it an absolute temperature. TEMP0 should be set to 273.0 if the Celsius scale is in use.

If CO is made equal to the Stefan-Boltzmann constant, sigma, (ie 5.6697 E-8 W*m**(-2)*K**(-4) ), times the emissivity of the surface, this creates a source having the magnitude:

emissivity * sigma * ( Tsurr ** 4 - Tsurface ** 4)

where T stands for absolute temperature on the Kelvin scale.

This is appropriate to radiative heat loss to (or gain from) surroundings at fixed temperature.

Core library case 608 illustrates the use of this feature.

The FREE-CONVECTIVE CASE is activated by following the * by a plus or a minus and then an integer. Thus:

PATCH(*+2NFACE,north,.........)
COVAL(*+2NFACE,TEM1,CO,VAL) or
PATCH(*-3EFACE,east,..........)
COVAL(*-3EFACE,TEM1,CO,VAL)

The former causes EARTH to provide a source equal to:
CO * (VAL - TEM1cell) ** 2 per unit north area,

and the latter causes EARTH to provide a source equal to:
CO * (VAL - TEM1cell) ** (1/3) per unit east area,

the sign being the same as that of (VAL - TEM1cell).


RADIB

-------- PIL real; groups 9 & 13 ---------

RADIB... is used to carry the radiation scattering coefficient in cases where the radiation model is activated.

See the help and encyclopaedia items on RADIAT, and GREX3 and GXRADI for further information.


Radius, inner, specifying the

(see RINNER)


Range

(Contour Edit Menu) -------------------------------------- Photon Help ----

Only contours within the specified band will be plotted. The colour scale for shaded and filled contours is determined by the lower and upper limit of the band.


REACTION-RATE representation

(See also PHENC entries: CHEMKIN, CREK & COMBUSTION)

REACTion-rates are represented in PHOENICS as sources or sinks (ie negative sources) of chemical species. The options provided in the standard GROUND coding are primarily intended for the representation of the diminution of fuel in combustion processes (see COMBUS ); but they can also be used for chemical reactions generally.

The options are provided in subroutine GXCHEMSO (for CHemical SOurces) which is called from group 13 of GREX when the first four characters of a PATCH name are CHSO. For example:

PATCH(CHSO,VOLUME,1,NX,1,NY,1,NZ,1,LSTEP)

would be used when the reaction zone is co-extensive with the domain of integration.

The options listed below are expressed in the form required for the source of the mass fraction of fuel, Mfuel, in the SCRS model of combustion described under the COMBUS entry.

where CHSOB is the rate-controlling parameter, and CHSOA is the stoichiometric mixture fraction (see COMBUS).


REAL

------ Command; defaults 0.0; group 1 - -

REAL....command to declare up to 100 real PIL variables. For example: REAL(RR1,RR2,RR3,RR4) makes RR1, RR2, RR3 and RR4 recognized as PIL variables.

Any name can be used, up to 6 characters, eg REAL(REYNOS).

Such variables can be set in the usual way (eg. RR1=3.1416);

they are also recognized on the right-hand side of assignment statements
(eg XULAST=RR1 sets XULAST to the current value of RR1 ie 3.1416 ).

They are recognized in arguments of other argument-setting commands, eg
COVAL(BOUND,P1,RR1,RR2) .

They can be combined by using arithmetic operators of the following types:
* / ** and brackets ( ) .

The operands can be any combination of integer and real numbers, PIL variables, array elements and user-declared variables.

Examples are:

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

The default provision of up to 100 variables can be enlarged by re-dimensioning in the MAIN program of the SATELLITE. See DIMENS for further information.


REALS

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

The following real variables are recognised by PIL:
ABSIZ ANGMIN AZDZ AZPH AZXU AZYV    
AZW1 BZW1 CFIPA CFIPB CFIPC CFIPD CFIPS CINH1A
CINH2A CMDOT CMDTA CORIOL CZW1 DARCON DIFCUT DRH1DP
DRH2DP DSTTOL DZW1 EL1 EL2 EL1A EL2A ENUL
ENULA ENUT ENUTA FIXCOR HUNIT ORSIZ OVRRLX PBAR
PHNH1A PRESS0 PRLC1A PRLH1A RELXC RELYC RELZC RHO1
RHO1A RHO2 RHO2A RINNER RLOLIM RSG1 RUPLIM SNALFA
TEMP0 TFIRST TLAST TMP1 TMP2 TMP1A TMP2A U1AD
U2AD V1AD V2AD W1AD W2AD WALLA WALLB  

The following real arrays are recognised by PIL:
CINT ENDIT EX FIINIT PHINT PRNDTL PRT RESREF
RG TFRAC VARMAX VARMIN XFRAC YFRAC ZFRAC  

The FLAGS entry includes a list of the real flags recognised by PIL.


RECIPROCAL /RECIPROCAL X /RECIPROCAL Y

---- Autoplot Help ----

REC[IPROCAL] [X or Y] {i j}

Data elements i-j will have the reciprocal taken of the X or Y values. SCALE will give a correctly scaled plot.


REDRAW

---- Autoplot Help ----

R[EDRAW] [i] [j]

Clear the screen and redraw data elements i - j only. If i and j are unspecified, the plot will be redrawn exactly as it was. Any items deleted or cleared will not be redrawn.


REDRAW

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

RE[draw].... is a REPLAY command which clears the screen, and redraws the current frame. If NOCLEAR is in effect, then all the frames comprising the current picture will be redrawn.

See also : REPLAY, SCALE, SHIFT, CLEAR, RESET


REDRAW

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

[Redraw] clears the screen, and redraws the current picture.


REDRAW

(Replay Menu) ------------------------------------- Photon Help ----

[Redraw] clears the screen, and redraws the current frame. If [NoClear] is in effect, then all the frames comprising the current picture will be redrawn.


Reference interphase friction formulae

(see CFIPA, CFIPB, CFIPC, CFIPD)


Reference interphase transport-coefficient

(see CFIPS)


Reference pressure

(see PRESS0)


REFINE command

(see TR218)


REFLIB

----- PIL real; Default=0.0 -------------

Used in conjunction with LIBREF when running test battery.


REGEXT

------ Command; group 2,3,4,5 -------

REGEXT....Command to set the default extent of all regions in a particular direction. Format: REGEXT(T or X or Y or Z, length) Note that this will reset the extent of ALL regions even if issued after GRDPWR commands.

For time distribution, the default region length is 1 second; for X, Y or Z directions the default region length is 1 meter.


Region

(Vector, Contour, Grid, Stream Menu) ------------------------------------- Photon Help ----

The current plotting region on the plotting plane.

See also: [Plane No.]


Region

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

The sequential number of the blocked region. The maximum is 10. If you type in any number that is less than the total number of block regions defined as seen near the bottom of the window, the limits of the blocked region will be shown and can be edited.


Region number, current, specifying in the X-direction

(see IREGX )


Region number, current, specifying in the Y-direction

(see IREGY )


Region number, setting in Z-direction

(see IREGZ)


Region number, setting of

(see LSTEP)


Regions of space, definition of

(see RESTRT)


Regions, number of, specifying in the X-direction

(see NREGX)


Regions, number of, specifying in the Y-direction

(see NREGY)


Regions, setting default extents for

(see REGEXT)


Regions, z-direction, setting number of

(see NREGZ)


Relational Data Input (RDI)

Whereas other CFD packages, and PHOENICS itself until 2007, allow the setting up of single-instance flow-simulation scenarios, the user of the latest PHOENICS can set up classes of scenarios, of which sub-sets are selected by way of user-chosen parameters.

To enable users to exploit the power of RDI, PHOENICS has been provided with a new front-end module, PRELUDE; and this, in conjunction with special-sector 'Gateways', enables users to introduce easily the data which they understand from their special knowledge to be necessary, without having to attend to matters not of their concern.

Another of its unique features is: In-Form, which allows users to augment the built-in capabilities of PHOENICS by adding new ones of their own.

Click here for a slide-show devoted to RDI.


RELAX

----- PIL Command; group 17 -------------- of the form:
RELAX(variable name,LINRLX or FALSDT , real constant)

  1. If the second argument is LINRLX,
    the 'real constant' is called the 'linear relaxation factor'. It is dimensionless.

    This setting affects the solution procedure by causing the increment of a solved-for variable to be multiplied by 'factor' prior to its addition to the in-store value of that variable.

    The factor is usually chosen to lie between 0.0 and 1.0, the lower values having the greater slowing-down effect on the solution.

    LINRLX is the default for the volume- fraction equations, for which the factor is 0.4 . Linear under- relaxation is often required for P1 in non-orthogonal grids in which NONORT=T.

    Two special cases should be noted:

    1. Linear relaxation of P1
      The setting RELAX(P1,LINRLX,0.0) sets pressure increments to zero; but this is done after these increments have been used for the calculation and application of the velocity adjustments they imply. This ensures that thee mass-imbalnces are rediced, cell-by-cell, at each iteration.
    2. Linear relaxation of P2
      RELAX(P2,LINRLX,factor), where 'factor' is a real number, has no direct effect on the pressure of the second phase, which is the same as that of the first phase.

      Instead it multiplies the continuity errors by 'factor' before they enter the pressure-correction sequence.
      This may be a more effective solution-smoothing sequence than under-relaxing the pressure correction itself, because it results in reduced (for 'factor' >1.0) velocity adjustments.

      (see entry for P2 ).

  2. If the second argument is FALSDT,
    the 'real constant' is called the 'false time step' . Its dimensions are those of time; so its units are, by default, seconds.

    Its effect is to add to the conservation equation for each cell a source equal to:

    (latest_phi - next_phi) / DTFALS(phi)

    where latest_phi is the current value of the variable being solved for, and next_phi is that which it will take after adjustment.

    Here the appearance of DTFALS(phi) in the denominator entails that its influence is greater the smaller is its value.

    Its importance as compared with other terms in the balance equation depends upon the size of the simulated space in the manner expressed by the following table.

    term proportional to and
    convection reference_length ** 2 * reference_velocity
    diffusion reference_length ** 1 *diffusion_coefficient
    chemical reaction reference_length ** 3 * reaction_rate
    time dependence reference_length ** 3 /time_step
    DTFALS reference_length ** 3 / false_time_step

    It follows that account should always be taken of the size of the domain, and of the order of magnitude of the other quantities appearing in the table, when assigning a value to DTFALS; and, since this is hard to do with confidence, it is better not to use false-time-step relaxaton at all.

    PATCH-wise false-time step under-relaxation can be introduced by means of PATCH and COVAL by using SAME as the fourth argument of COVAL.


Relaxation

More properly called 'under-relaxation', this is a technique used for preventing the built-in iterative solution process from 'diverging', i.e. failing to 'home in on' unchanging values as the iterations continue.

It thus assists to procure convergence (q.v.). The most common means of achieving it is by assigning 'value' in the PIL connabd: RELAX(variable name,LINRLX or FALSDT, value). (See RELAX)


RELIABILITY of predictions

See VALIDATION


RELXC

----- PIL real; default=1.0; group 6 -----

RELXC.... linear relaxation parameter for influencing the solution of the coordinate XC when MAGIC(L) is in use. A value of 1.7 is often found to accelerate the rate of convergence of the solution.


RELYC

----- PIL real; default=1.0; group 6 -----

RELYC.... linear relaxation parameter for controlling the solution of the coordinate YC when MAGIC(L) is in use.

See RELXC for advice.


RELZC

----- PIL real; default=1.0; group 6 -----

RELZC.... linear relaxation parameter for controlling the solution of the coordinate ZC when MAGIC(L) is in use.

See RELXC for advice.


Replace

(Test Menu) ------------------------------------ Photon Help ----

[Replace] modifies an existing text string with a new one. Pick the text string to be modified first then PHOTON will prompt for the new string. Type the new string in the input window near the bottom of the window.


REPLAY

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

REP[lay]....is used to display frames from previously created SAVE files. It causes the program to enter 'replay mode', within which only the following REPLAY commands are available :-
FILE LIST DRAW SENDP DUMP REDRAW SCALE SHIFT
RESET WHERE 4VIEW TEXT MONOCHROME CLEAR NOCLEAR  

Help entries are available for all these commands - type 'command ?' to view the help entry for a given command.

See also : SAVE


REPLAY

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

[Replay] is used to display frames from previously created SAVE files. It activates the 'replay sub-menu'. Immediately after each drawing, the replay menu is invisible. Pressing any key or a button of the mouse will pop up the menu to the screen.


RESET

------- PIL logical; group 19 default = F -

When RESET=T in Q1, the subroutine GXRSET (in the file PHOENICS/d_earth/d_core/gxsettim.htm) is called. This monitors the step-to-step change of a user-selected variable, and adjusts the time step if the change is too small or too big.

The field values of the chosen variable are summed over the whole domain, and then averaged by the number of cells.

If the change-limits are exceeded, the time step is reset, and the time step is repeated.

The control parameters are:
ISG10 - index of the variable to be monitored.
RSG10 - minimum acceptable change in average value.
RSG11 - maximum acceptable change in average value.
RSG12 - factor used to adjust time step, usually about 0.9.

The new time step is estimated from:

IF ( average change <RSG10 or> RSG11 ) THEN Dtnew = Dtold * RSG11 * RSG12 / (abs(average change)) ENDIF


RESET

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

RE[set].... is a REPLAY command which resets the position and scaling used for plotting frames to the default values, which are full size, origin at 0,0. It also deletes any stored frames and resets the display mode to CLEAR.

See also : REPLAY, SCALE, SHIFT, CLEAR, REDRAW


RESET

(Results Menu)-------------------------------------- Photon Help ----

[Reset] resets the position and scaling used for plotting frames to the default values, which are full size, origin at 0,0. It also deletes any stored frame and resets the display mode to CLEAR.


Reset

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

Reset all the view parameters (view direction, UP direction, magnification factor...) to the default.


RESFAC, the residuals factor

RESFAC is a PIL variable, defaulted to 0.0001, used by PHOENICS, when the PIL variable SELREF = T (its default value), for determining if the solution has converged. When the reference residual, RESREF, for each variable falls below RESFAC the calculation will terminate. RESREF is calculated from:

RESREF =  typical flow rate of the variable.

The "typical flow rate" is the sum of the absolute values, for all cell volumes and cell faces, of the convection fluxes, diffusion fluxes, sources and transient terms. It is calculated internally, within the PHOENICS solver module; and its dimensions are: (mass per unit time) * (property per unit mass) .

Thus,

Users should be aware that the employment of SELREF=T, with a value of RESFAC which is the same for all variables, is a convenient but crude method of controlling the cut-off point of the solution procedure. To set SELREF = F, and set the individual RESREFs for themselves may be safer, when obtaining a well-converged solution is especially important.

Input-library cases 530 and 531 have been designed to enable the influence of RESFAC to be explored.

See also the PHENC entry for RESREF.


Residuals

These are imbalances (errors) in the finite-volume equations which are computed during the solution procedure, the aim of which, of course, is to reduce them to an acceptable magnitude.

Their magnitudes can be reported to the user, variable-by-variable, in two ways, namely as:

  1. global values, which are the sums of the absolute values for all cells; or

  2. fields of values, which can be printed in the RESULT file, or viewed by means of PHOTON, AUTOPLOT or the VR-Viewer, in the same manner as for other SOLVEd or STOREd variables.

The global values are appear both in the result file, where they are influenced by the setting of ITABL and in and in the graphical monitor, if that is activated.

The most convenient means of printing and plotting the field values of residuals (and of "corrections" also) is to make use of the In-Form function RESI (and the function CORR for corrections.)  For example, the residual of the temperature equation,TEM1, can be placed in the 3D variable T1R by the command

(STORED of T1R is RESI(TEM1))

However, the older-established method described in the next paragraphs is still available, though are not recommended.

When a solved-for variable is given the name xxx% and the statement STORE(xxxR) appears in the Q1 file, the field of xxxR contains the values of the residuals of variable xxx% before entry to the linear-equation solver.

These values can be printed in the result file, or viewed via PHOTON or AUTOPLOT, in the same was as other stored variables.

When, further, the statement STORE(xxxC) appears in the Q1 file, the field of xxxC contains the values of the corrections to variable xxx% after exit from the linear-equation solver.

These values can be printed in the result file, or viewed via PHOTON or AUTOPLOT, as for other stored variables.


RESREF, the reference-residual for a solved-for variable

RESREF(variable name) is PIL variable, which may be set in the Q1 file, or by way of the menu.

However the there-set value will be effective only if the PIL variable SELREF, the default of which is T, is set to F. Otherwise the values set by the user will be over-written (See PHENC entry: RESFAC).

When the sum of the absolute value of the residuals for all variables falls below the associated RESREF, the solution as a whole is terminated. In this case, one more sweep of the domain is performed to give print-out, but no solving is done.

GROUND is informed about the termination of iterations and sweeps by the two logical variables ENUFIT and ENUFSW. When the slab-wise iterations ( governed by LITHYD ) terminate, ENUFIT is set to T; when the sweeps are terminated, ENUFSW is set T.

In the RESULT file, the print-out of the whole-domain residual sum for each variable is normalized by its RESREF; therefore printed values below RESFAC signify that the convergence criterion has been satisfied.

The diminution of the residuals during the course of the solution may be observed by way of the graphical monitor, activated by TSTSWP=-1, as shown in the following picture. In the case shown, none of the residuals has fallen to the reference value.

GAS-TURBINE COMBUSTION CHAMBER


RESTRT

---- Command; group 11 --------------

RESTRT(variable name 1,variable name 2,...etc.) is a command which instructs EARTH to read the initial fields of the specified variables from the restart file.

Restart files ( named PHI or PHIDA by default according to the presence in the PREFIX file of the lines PHIDA=F or PHIDA=T respectively) are created in runs for which the PIL variable, SAVE, equals T ( which is the default )
except when given a different name by the PIL statement:
NSAVE = four-character file name.

NSAVE names the file to which the fields are dumped at the end of a run; but to instruct EARTH to take its values from that file, the command:

NAMFI = four-character file name

must appear in the Q1 file.

The RESTRT command permits the user to select which of the fields on the restart file he wishes to use as the initial fields of a subsequent calculation. In addition to those fields selected from the restart file, new variables can be introduced for storage and solution on any restart run.

The most common use of RESTRT is to perform "continuation runs" by means of the instruction RESTRT(ALL), which ensures that all variables will be read. FSWEEP may be set to the last sweep of the previous plus one, so as to keep track of the number of sweeps to date.

RESTRT(phi) acts by setting FIINIT(phi) equal to the flag READFI, (signifying "read from a file")

Its effect can be undone by re-setting FIINIT(phi) to any other value.

RESTRT(NONE) will reset all FIINIT values to 1.0E-10.

Special care is needed when restarts are to be made from runs in which the GCV algorithm is in use for a multi-block grid.
The reason is that, to permit PHOTON to represent such flows properly, the dumped is modified; but the modification renders the file unsuitable for restarting.
The modification is not made however when both nsave and namfi are both set to the same name, eg 'othr', for this is taken by EARTH as a signal that a restart is intended.

See FIINIT for further information.


REYNOLds-stress turbulence-model

-----------

(also referred to as RSTM)

See PHOENICS encyclopaedia file, Turbulence Models in PHOENICS: Reynolds-stress turbulence model


RG array

RG array This array of real variables can be set in SATELLITE and is recognised by GX-type subroutines if the appropriate COMMON is included. When it was first introduced, RG was intended to be kept available for users who were writing their own GROUND subroutines. However, its use has spilled over into subroutines made available to ALL users. Therefore, in preparation for the launch of version 2, this excessive use was curbed in accordance with the rules:-

  1. RG may be used by CHAM programmers ONLY for special-purpose programs such as ESTER and HOTBOX, but by non-CHAM users for anything else they desire;
  2. Different variables must be introduced to convey from SATELLITE to GROUND such real-variable data as are needed for general-purpose (GX..) subroutines.
  3. If insufficient variables are available in SATEAR or GRDLOC, the necessary information must be conveyed by use of SPEDAT, RQ1R, etc.

Similar remarks apply to the arrays IG( ), LG( ) and CG( ).


RG2D

RG2D is an integer index, usable in subroutines called from GROUND, for accessing the 2D array of values, pertaining to the current IZ-slab, of:

distances from the axis of symmetry to the cell centres. RG2D is of significance only in cylindrical-polar coordinates, i.e. when CARTES=F and BFC=F.


RGRAD

----- PIL real flag; value= 14.0; group 13 -

RGRAD....is a PATCH type, to provide by means of COVAL momentum sources of magnitude equal to:


(cross-sectional area in direction of velocity)*0.5*
(sum of phase volume fractions on either side of velocity node)
*(decrement of volume fraction in the velocity direction)
*(the quantity appearing in the "value" argument of COVAL) .

Momentum sources of this kind occur when shallow layers of fluid are influenced by gravity. Then the "value" is the fluid density times the gravitational acceleration, times the vertical height of the channel cross-section.

The first three terms in the above expression represent the proportion of the cross-sectional area over which the associated pressure difference operates; and it is valid only for wide or rectangular-sectioned channels.

If the cross-section is not rectangular, the RGRAD option should not be used. Subroutine GXLATG ( for lateral gravity ) called from GREX provides the option valid for a pipe of circular cross-section. It makes use of the functions FN101, FN102 and FN103. See the GRAVity entry for further information.

The third (coefficient) argument of COVAL has no significance for RGRAD-type PATCHes, and is best set to zero.


RHO1

------ PIL variable; Real; default= 1.0; group 9

RHO1 signifies the density of the first phase.

Contents


RHO1 greater than zero

If RHO1 is given a positive value, that value is used for the first-phase density by EARTH.

Recourse to GROUND is necessary when the density is a function of other variables. The following options have been provided in subroutine GXDENS called from within EARTH; they are selected as indicated below:-


RHO1 = GRND1

RHO1=GRND1 selects one of the following:

  1. density = RHO1A+RHO1B*h1 , where h1 is the enthalpy variable stored in H1 (i.e. variable number 14). This is the default condition.

    or

  2. If RHO1C > 0 then; density = RHO1A + RHO1B*NAME(RHO1C)

    or

  3. If IBUOYB > 0 and IBUOYA = 0 then; density = RHO1A + RHO1B*NAME(IBUOYB) + RHO1C*NAME(IBUOYC)

    or

  4. If IBUOYB > 0 and IBUOYA > 0 then density = RHO1A+RHO1B*NAME(IBUOYB)+RHO1C*NAME(IBUOYC)+ RHO2A*NAME(IBUOYA)

RHO1 = GRND2

RHO1=GRND2 selects: density=1./(RHO1A+RHO1B*h1) .


RHO1 = GRND3

RHO1=GRND3 selects: density=RHO1A*(p1+PRESS0)**RHO1B+RHO1C, where p1 is the relative pressure stored in P1. This option is the one to use for isentropic gas flow.


RHO1 = GRND4

RHO1=GRND4 selects: density=RHO1A+RHO1B*t1, where t1 is the first phase temperature stored in T1 ( see also TMP1 ).


RHO1 = GRND5

RHO1=GRND5 selects one of the following:

  1. If RHO1A=0 then; density=
    RHO1B*(p1+PRESS0)/(t1+TEMP0)

    This option is the one to use for ideal-gas flow with constant gas constant, 1/RHO1B

    or

  2. If RHO1A > 0 then; density=
    (p1+PRESS0)/((RHO1A*(1-C1)+RHO1B*C1)*(t1+TEMP0))

    This option is the one to use for ideal-gas flow with species- dependent gas constant.

Here:

In both cases p1 is the relative pressure stored in P1 and t1 is the first phase temperature stored in T1 determined by the ascription of TMP1, or TEM1, depending on whether H1 or TEM1 is solved.


RHO1 = GRND6

RHO1=GRND6 is for use with the simple chemical reaction scheme of combustion ( see COMBUS ).

This option sets, density=
(p1+PRESS0)*Wmix/(8314.3*t1), where:
the mixture molecular weight is computed from:


RHO1 = GRND7 Setting rho1 to GRND7 activates the seven-gases options, which is often used for the simulation of hydrocarbon-air combustion.
RHO1 = GRND8 Setting rho1 to GRND8 activates the density options of the special-purpose program PHOENICS-CVD if this forms part of the installation.
RHO1 = GRND9 Setting rho1 to GRND9 activates the density options of the CHEMKIN add-on.
RHO1 = GRND10 Setting rho1 to GRND10 sets density as the reciprocal of a linear function of temperature.

If these options failed to meet the user's needs, in the past, he or she would have had to set RHO1=GRND and to provide Fortran coding in subroutine GROUND, in GROUP 9 SECTION 1.

Nowadays however it is preferable to use either the In-Form feature, or PLANT.

See the PHENC entry for GROUND for examples of this.

For the density formulae which imply a strong pressure dependence, the variable DRH1DP should be set accordingly. DRH1DP is set automatically in options GRND3 and GRND5.


RHO1A

----- PIL real; default= 0.0; group 9, se -

RHO1A....parameter used in phase-1 density formulae. Further parameters of the same kind are: RHO1B,RHO1C.


RHO2

------ PIL real; default= 0.0; group 9, se -

RHO2....density of the second phase, used similarly to RHO1.
See RHO1 for further information.

The following feature is useful when shallow-water theory is extended to the simulation of waves on deep water:
RHO2 is used to convey what the reference density is; but it is given a negative sign so as to signal that this is its ( unusual ) role.


RHO2A

----- PIL real; default= 0.0; group 9, se -

RHO2A....parameter used in phase-2 density formulae. Further parameters of the same kind are: RHO2B,RHO2C.

RightHand/LeftHand System

---------------- R Photon Help ----

[Right/LeftHand System] changes the coordinate system to a left-handed or a right-handed coordinate system. The default is [RightHand System].


RINNER

---- PIL real; default= 0.0; group 4 --- -

RINNER....Inner radius, i.e. the distance from the axis of symmetry to the cylinder y=0. The default setting of zero therefore corresponds to the straightforward cylindrical-polar coordinate system in which y is measured from the axis of symmetry.

RINNER can be set greater than zero, for example to specify the flow through an annulus, or for the calculation of flow over of a body of revolution whose shape, in parabolic flows, may be distorted by SNALFA.


RLOLIM

---- PIL real; default=0.0; group 8 -----

RLOLIM....For DONACC=T, set to the value of the volume fraction of phase 1 below which cell will be regarded as being empty of this phase.

RLOLIM can also be used to prevent interphase friction from vanishing when the volume fraction is zero: see CFIPS for details.


RLXU1

------------ PIL real; default=1.0

RLXU1... is underrelaxation factor for U1


RLXV1

------------ PIL real; default=1.0

RLXV1... is underrelaxation factor for V1


RLXW1

------------ PIL real; default=1.0

RLXW1... is underrelaxation factor for W1


RNG-derived KE-EP turbulence model

See PHENC entry: RNG-derived KE-EP turbulence model


ROTAXA

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

ROTAXA... is used in GXROTA for BFC cases with rotating coordinate systems to specify the x-value of one of a pair of points that define the axis around which the rotation occurs. See the help and PHENC items on ROTA, and GXROTA for further information.


ROTAXB

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

ROTAXB... is used in GXROTA for BFC cases with rotating coordinate systems to specify the x-value of one of a pair of points that define the axis around which the rotation occurs. See the help and PHENC items on ROTA, and GXROTA for further information.


ROTAYA

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

ROTAYA... is used in GXROTA for BFC cases with rotating coordinate systems to specify the y-value of one of a pair of points that define the axis around which the rotation occurs. See the help and PHENC items on ROTA, and GXROTA for further information.


ROTAYB

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

ROTAYB... is used in GXROTA for BFC cases with rotating coordinate systems to specify the y-value of one of a pair of points that define the axis around which the rotation occurs. See the help and PHENC items on ROTA, and GXROTA for further information.


ROTAZA

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

ROTAZA... is used in GXROTA for BFC cases with rotating coordinate systems to specify the z-value of one of a pair of points that define the axis around which the rotation occurs. See the help and PHENC items on ROTA, and GXROTA for further information.


ROTAZB

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

ROTAZB... is used in GXROTA for BFC cases with rotating coordinate systems to specify the z-value of one of a pair of points that define the axis around which the rotation occurs. See the help and PHENC items on ROTA, and GXROTA for further information.


ROTOR, a PHOENICS-VR object type

A ROTOR object is used to define a region of rotating coordinates with a static cylindrical-polar grid. See the description in the PHOENICS_VR Reference Guide, TR326


Rows, setting number of

(see NROWCO)


RS

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

Integer flag; value=11.

RS....standard name used to denote the second-phase shadow volume fraction, i.e. that which would be present in the absence of inter-phase mass-transfer. RS is especially useful for the simulation of particle combustion.
See PHI , NAME and prtsiz for further information.


RSTGEO

---- PIL logical; default= F; group 6 --- -

RSTGEO....may be set to T to initiate a BFC geometry restart. When done this ensures that all the geometrical quantities required for BFC working are read from the pre-existing file, which must have been created in an earlier run by setting SAVGEO to T. Normally, when RSTGEO is set T, SAVGEO should be set F for there is no need to save the geometry on each run, especially as the act of so doing may be time-consuming. Note that on some systems the time taken to read the file may be greater than the cpu time taken to re-calculate all the geometrical quantities.


RSTM

------ PIL logical; default=F; group 19 --- - < 95:13>

Set RSTM=T to activate the Reynolds-stress turbulence-model.

See Reynolds-stress Turbulence Model


Ruled grids in AUTOPLOT

A grid made up of dashed lines parallel to the axes, at intervals corresponding to the axis calibrations, may be ruled on the plot by the command GRID. A second GRID command will remove the grid again, and further repetitions of the command will alternately restore it and remove it.

You can obtain more closely-spaced grids by using the command GRID DEFINE, which enables you to specify the intervals you require.

For logarithmically-scaled axes, the GRID command will draw a ruled grid at the powers of ten. To rule a finer grid based on the subsidiary calibrations, you should use the GRID DEFINE command. As usual, this will request grid spacings in the x-and y-directions. In a direction plotted logarithmically, you must enter a number for the grid spacing, although it will not be used. In a direction plotted linearly, the number you enter will be used for the grid spacing (as is always the case for linear plots).


RUN

This PIL command is the second item (after TALK) on the first line of the Q1 file. This line often appears thus:
TALK=T; RUN(1,1),
where the arguments 1,1 signify that only the first run appearing in Q1 is to be read by the SATELLITE, i.e. all the PIL statements following this line up to the first STOP will be read.

When the Q1 contains more than one STOP, with a distinct set of PIL statements between each, RUN can be used to select which set (or sets) is (or are) to be used.

Thus, RUN(10,20) would cause the SATELLITE to read the 11 sets of statements following the 9th STOP up to the 20th STOP.

RUN can also be used to select individual sets in the range indicated Thus, RUN(10,20:12,15,19) would cause runs 12, 15 and 19 to be read.


Run titles and other preliminaries

(GROUP 1)


runaut

Command-line entry which starts the execution of AUTOPLOT on any system.


runear

Command-line entry which starts the execution of the Windows/Intel or Unix/Linux version of the PHOENICS flow-solver module, EARTH.


Running PINTO

(see TR218)


runpho

Command-line entry which starts the execution of the Windows/Intel or Unix/Linux version of the PHOENICS graphical-display module, PHOTON)


runpin

(A command to run PINTO)


RUNPHO

(A command to run PHOTON)


runsat

This command causes the Windows/Intel PHOENICS-Input module (SATELLITE) to begin execution


RUPLIM

---- PIL real; default= 0.0; group 8 --- -

RUPLIM....For DONACC=T, set to value of R1 (volume fraction of phase 1) above which cell will be regarded as being full of this phase.


RV2D

RV2D is an integer index, usable in subroutines called from GROUND, for accessing the 2D array of values, pertaining to the current IZ-slab, of:
distances from the axis of symmetry to the north wall of the continuity cells, at which the v velocities are stored.
RV2D is of significance only in cylindrical-polar coordinates, i.e. when CARTES=F and BFC=F.

Note that this index is present only if CALL MAKE(RV2D) is present in Group 1, Section 1 of GROUND.


wbs