Encyclopaedia Index

LABEL LAM-Bremhorst KE-EP turbulence model. LAMINAR LAMPR
Large Eddy Simulation LASLPA/PB LBNAME LBO LCOALA
Lectures
LEN1/2 Length scale of phase 1/2 LES LEVEL
LF LF0 LFS logical variable LG LIBRARY (Input-File) LIBREF LIJ LIK LINE

LINK LINRLX LINVLX LINVLY LINVLZ LIST LITC LITER LITFLX LITHYD LITTLE LITXC LITYC LITZC LJK LN/X/Y LOAD LOCAL LOCATE LOCKING LOG/X/Y LOG LOGICAL LOGREAD LOGO LONGNAME LOOP LOW LOW REYNOLDS NUMBER

LSGx LSOLID LSTEP LSWEEP LTLS LVEL
LVEL turbulence model
LWALL LWP


LABEL

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

LABEL identifies the target for a PIL GOTO statement. The syntax is LABEL name, where name is a string of up to 68 characters.

See the entry on GOTO for further information.


LAM-Bremhorst KE-EP turbulence model.

See the PHENC entry: Lam-Bremhorst KE-EP Turbulence Model

Laminar kinematic viscosity

(see ENUL, VISL)

Laminar kinematic viscosity, formulae for

(see ENUL)

Laminar Prandtl number

(see PRNDTL)

Laminar Prandtl number, formulae for

(see PRNDTL)

Laminar Prandtl number, setting variable of

(see PRNDTL)

LAMPR

LAMPR is an integer index, usable in subroutines called from GROUND, for accessing the 2D array of values, pertaining to the current IZ-slab, of:K
the PRANDTL number. Alternatively, if -GRND = PRNDTL(phi) GRND10, this index is used instead to set the z-slab values for diffusivities.

LASLPA

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

There is currently no help for this item


LASLPB

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

There is currently no help for this item


LBNAME

LBNAME is a function returning the "block-location index" of a variable which is available for use in EARTH.

Its significance and us are explained in the PHENC entry: F-array of EARTH.

Its argument is the four-character string representing the NAME of the variable issued by the SATELLITE.

LBNAME is case-sensitive; so since some SATELLITE operations can replace lower-case characters by upper-case ones, it is safest to use upper-case characters only.


LCOALA

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

There is currently no help for this item


LEN1

------ Integer name; default=0; group 7 -

LEN1.... indicates which whole-field store will be used for the length scale of phase 1 in response to the command STORE(EL1). Such storage is necessary when it is desired to under-relax this scale. Once stored, this field should be initialized in group 11.


LEN2

------ Integer name; default=0; group 7 -

LEN2.... indicates which whole-field store will be used for the length scale of phase 2 in response to the command STORE(EL2). Such storage is necessary when it is desired to under-relax this scale. Once stored, this field should be initialized in group 11.


Length scale of phase 1

(see EL1 integer name, Group 9)

Length scale of phase 2

(see EL2 integer name, Group 9)

LEVEL/LEVEL X/LEVEL Y

---- Autoplot Help ----

LE[VEL] [X or Y] [a] Draws a line of constant x or y with a value a. The program will prompt for unspecified quantities.

See also HELP on : LEVEL CLEAR, LEVEL DELETE


LEVEL CLEAR

---- Autoplot Help ----

LE[VEL] CL[EAR] Clears all levels from memory. REDRAW for a 'clean' plot.

See also HELP on : LEVEL X, LEVEL Y, LEVEL DELETE, REDRAW


LEVEL DELETE

---- Autoplot Help ----

LE[VEL] DE[LETE] Deletes last level entered. REDRAW for a 'clean' plot.

See also HELP on : LEVEL X, LEVEL Y, LEVEL CLEAR, REDRAW


LEVEL KEEP

---- Autoplot Help ----

LE[VEL] K[EEP]

Levels will not be cleared from memory by a CLEAR command, but will be retained for the next plot.

See also HELP on : LEVEL X, LEVEL Y, LEVEL CLEAR, LEVEL DELETE


LFS logical variable


LG

-------- Logical array; default=F; group -

LG....is an array for transferring to subroutine GROUND any logical data that the user may need there.


LIBREF

---- Integer; default=0; group 1 ---- -

LIBREF....is the reference number of the Input Library case currently LOADed in the instruction stack. When the instruction LOAD(case-number) is executed, the case is loaded into the instruction stack, and

LIBREF = case number
is automatically appended.

LIJ

------- Logical; default=F; group 6 ---- -

LIJ....when =T, specifies that MAGIC(L) will solve for the cartesian coordinates XC and YC with ZC fixed, on the planes constant K indicated by the currently-active DOMAIN.


LIK

------- Logical; default=F; group 6 ---- -

LIK....when =T, specifies that MAGIC(L) will solve for the cartesian coordinates XC and ZC with YC fixed, on the planes constant J indicated by the currently-active DOMAIN.


Line

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

[Line] draws a straight line in the current domain. The two points are typed in from the input window.


Line, setting of

(see GSET(L,...))

Line-printer plots, format of

(see IPROF)

Linear-equation solver, user's own

(see USOLVE)

Linear-relaxation, specifying the

(see RELAX, LINRLX, RELXC, RELYC, RELZC)

Linearization, control of

(see KELIN)

LINRLX

---- Integer flag; value=0; group 17 -

LINRLX.... should be entered as the second argument of RELAX when the linear mode of under-relaxation is to be used.


LINVLX

---- Real flag; value=27.0; group 11 -

LINVLX....is a PATCH type used for initialization of field variables in group 11. This type permits the specification of a linear variation in the X direction of field variables identified via INIT. The 3rd argument of INIT specifies the x-wise gradient, and 4th argument of INIT specifies the value required in the first IX location of the PATCH.

Do not use LINVLX when BFC=T; instead use PATCH name IBFC ( see PATCH for further details ).

See INIT, LINVLY and LINVLZ for further information.


LINVLY

---- Real flag; value=28.0; group 11 -

LINVLY....does for the y direction what LINVLX does for the x direction. See LINVLX for details.


LINVLZ

---- Real flag; value=29.0; group 11 -

LINVLz....does for the z direction what LINVLX does for the x direction. See LINVLX for details.


LIST

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

LI[st].... is a REPLAY command to scan the currently open SAVE file, and list the title of each frame. If no title was specified at the time the frame was saved, the message 'no title' is output. The FILE command must have been used to open a SAVE file before LIST can be used.

See also : REPLAY, FILE


LITC

------ Integer; default=1; group 15 --- -

LITC....is the number of iterations at a slab during a sweep of the solution cycle encompassing the variables with indices from 12 upwards. This loop is within the loop of which LITHYD is the counter limit, but unlike the LITHYD loop it does not extend to the solution of the velocities and the slab-wise pressure corrections.

Values in excess of 1 may be useful if several such variables interact strongly, as in the case of chemical reaction. Unless the user has good reason for doing otherwise he is advised to leave LITC at its default value.


LITER

----- Integer array; group 16 -------- - default=various

Definition

LITER(phi) is the maximum number of iterations which are to be performed by the linear-equation solver for the variable phi,

For one-dimensional operations (eg at "slabs" for which NX=1 or NY=1, or for the whole field when only NZ is greater then 1), the linear equations are solved directly; so that, whatever the original setting, LITER is taken as 1.

Watching its effect

In order see how the solver reduces the residuals of the equations more the larger is LITER,set LITER(phi) to minus the number wanted as a signal that a plot of the residuals should be shown on the VDU.

This print-out comes at an iteration frequency of TSTSWP.

Information about the progress of the linear-equation solvers can also be directed to the main output ( ie. to the file RESULT ), by means of the third argument of OUTPUT.

Choosing the value

The larger the value chosen for LITER, the longer the time which will be spent in the solver, and the smaller will be the resulting residuals.

However, in most CFD problems the coefficients in the equation are influenced by changes in other solved-for variables. Therefore it may be economical to set a low value of LITER, in order that the coefficientsmat be updated more frequently.

The only general rule that can be propounded is that there is usually an optimum value which can be didvovered, however only by experiment.

An example

Library case 274 was run nine times, each with a different LITER(P1) by way of the following Q1 file:

            talk=f;run(1,9)
            load(274)
            lsweep=500
            liter(p1) = 1
            stop
            load(274)
            lsweep=500
            liter(p1) =  2
            stop
            load(274)
            lsweep=500
            liter(p1) =  5
            stop
            load(274)
            lsweep=500
            liter(p1) = 10
            stop
            load(274)
            lsweep=500
            liter(p1) = 15
            stop
            load(274)
            lsweep=500
            liter(p1) = 20
            stop
            load(274)
            lsweep=500
            liter(p1) = 30
            uwatch=t
            stop
            load(274)
            lsweep=500
            liter(p1) = 50
            stop
            load(274)
            lsweep=500
            liter(p1) = 100
            stop                 
The following shows the results.
liter(p1)run timenumber of sweeps
1 49 467
2 32 295
5 30 280
10 27 242
15 28 256
20 27 236
30 31 267
50 33 280
100 36 303

Inspection shows that the optimal value of LITER(p1) is between 10 and 20 for this case.

For problems with larger cell numbers, the optimal value is likely to be larger.


LITFLX

---- Integer; default=1; group 15 --- -

LITFLX....maximum number of iterations on convection-flux-, volume-fraction- and interphase-mass-transfer-calculations. It is for use in two-phase calculations only.

The calculation of the quantities mentioned is the first work done at a slab. LITFLX values greater than unity permit the establishment of a self-consistent set of mass fluxes and volume fractions for subsequent use at the slab: this can sometimes promote convergence.


LITHYD

LITHYD does for a slab in a parabolic flow what LSWEEP does for the whole domain in elliptic flow; and the whole-slab iterations may be terminated, as are the whole-domain ones allowed by LSWEEP, by the falling of the residuals below the user-set values of RESREF. What has been written in Section 5.5(a) therefore applies here also, except that the decision to terminate solution at a slab is subject to the sum of the absolute residuals falling below RESREF*NZ.

However, two further points should be mentioned. First, slabwise iterations can be employed for elliptic problems (ie LITHYD may be set to exceed 1); and convergence may indeed be accelerated by this practice if the flow direction is entirely from low z to high z, especially when the domain is long and thin, and the w component of velocity is always positive.

Secondly, if NZ equals unity, so that only one slab is in question, it is almost immaterial whether LSWEEP or LITHYD is used to control the amount of computational work which is done; but it is probably simpler to set LITHYD to unity and rely only on LSWEEP.


LITHYD

---- Integer; default=1; group 15 --- -

LITHYD....maximum number of hydrodynamic iterations at a slab. This iteration loop covers all solved variables, and includes the solution of the slab pressure-correction equation ( when the N appears as the fourth argument of SOLUTN for P1 ).

For parabolic calculations ( PARAB=T ), LITHYD should always be given a value greater than 1 ( say 10 ). The slab-iteration-loop will then be terminated either after LITHYD iterations, or when the RESREF conditions are met.


LITTLE

---- Autoplot Help ----

LIT[TLE]

Produces plots which will copy directly into a CHAM half-page report box. Default text size is size 4

See also HELP on : BIG, FULL, PAGE


LITXC

----- Integer; default=5; group 6 ---- -

LITXC.... number of inner iterations for the cartesian coordinate XC in MAGIC(L). Often one of the coordinates, eg. XC, converges to a fixed value before the other coordinates do, eg. YC and ZC. In this circumstance set LITXC=0 for economy.


LITYC

----- Integer; default=5; group 6 ---- -

LITYC.... number of inner iterations for the cartesian coordinate YC in MAGIC(L). See LITXC for further information.


LITZC

----- Integer; default=5; group 6 ---- -

LITZC.... number of inner iterations for the cartesian coordinate ZC in MAGIC(L). See LITXC for further information.


LJK

------- Logical; default=T; group 6 ---- -

LJK....when = T, specifies that MAGIC(L) will solve for the cartesian coordinates YC and ZC with XC fixed, on the planes constant I indicated by the currently-active DOMAIN.


LN /LN X /LN Y

---- Autoplot Help ----

LN [X or Y]
Changes x- or y- axis to a natural log scale. Repeated use of the command will continue taking logs. Negative values are trapped to 1.0E-6, and will not be recovered on return to linear scale. The plot will be redrawn with the correct axis scaling using the SCALE command. ALN reverses the process.

See also HELP on : ALN, SCALE, LOG, ALOG


LOAD

The PIL LOAD command, which can be edited into a Q1 file or issued during an interactive SATELLITE session, has the following functions:

  1. to fetch and interpret a complete Q1 file from one of the Input-File Libraries; or
  2. to fetch and interpret a PIL macro.

Its syntax is:

Loading a Q1 file or macro has the effect of wiping out whatever already exists in the 'instruction stack' and restoring the default settings,
unless:

  1. the said stack already contains the statement:
    NOWIPE = T
    or
  2. the name of the loaded file is preceded by a dollar sign, as in:
    #$unigrid
    .

The following additional points should be noted:


Local arrays, declaration of

(see ARRAY)

LOCATE

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

The syntax is : LOCATE(ARRAY,VALUE,IP)

LOCATE tries to find the VALUE in an array ARRAY, and returns the index in IP. If the value is not found, IP is set to -999. For 2 and 3D arrays there are 2 and 3 extra arguments respectively. One is ?, indicating the dimension to be searched, and the other(s) set the row/column/plane. For example, if AR1(4,8)=0.5, then:

LOCATE(AR1,.5,IP,?,8)
would return IP=4, and
LOCATE(AR1,0.5,IP,4,?)
would return IP=8. IP can be any valid PIL integer, and ARRAY can be any valid PIL array.

Locking

A hardware or software device which is used to ensure that PHOENICS runs only on the machine it is licensed for, using the features that have been licensed, for the duration of the licence.

LOG /LOG X /LOG Y

---- Autoplot Help ----

LO[G] [X or Y]

Changes x- or y- axis to log base 10 scale. Repeated use of the command will continue taking logs. Negative values are trapped to 1.0E-6, and will not be recovered on return to linear scale. The plot will be redrawn with the correct axis scaling using the SCALE command. ALOG reverses the process.

See also HELP on : ALOG, SCALE, LN ALN


LOG

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

LOG opens the named LOG file in which all subsequent commands in the current interactive session or from a USE file are recorded. The LOG file can be used as a USE file in a later session.


LOGO

---- Autoplot Help ----

LOGO
The CHAM logo will alternately appear and disappear from the bottom right-hand corner of the plot. The location of the logo can be changed with LOGO MOVE, and its size with LOGO SCALE.


LONGNAME

LONGNAME is a SPEDAT "context" name, the function of which is best illustrated by consideration of an example. Library case N131 will serve.

This case is used for comparing the merits of various numerical schemes, each of which is applied to a distinctly-named variable.

Thus:

and so on.

This is satisfactory; but the long-established 4-character limit to the NAME variable, places some burden on the user's memory.

Recent versions of PHOENICS resolve the difficulty by permitting a 40-character 'longname' extension to be added, by inclusion in the Q1 file of lines such as the following:

    
SPEDAT(LONGNAME,USOL,C,Upwind)
SPEDAT(LONGNAME,CSOL,C,Cds)
SPEDAT(LONGNAME,QSOL,C,Quick)
SPEDAT(LONGNAME,LSOL,C,Linear_upwind)
SPEDAT(LONGNAME,3SOL,C,Cubic_upwind)
SPEDAT(LONGNAME,FSOL,C,Fromm's_scheme)
SPEDAT(LONGNAME,SSOL,C,Smart)
SPEDAT(LONGNAME,KSOL,C,Koren )
SPEDAT(LONGNAME,MSOL,C,Minmod)
SPEDAT(LONGNAME,VSOL,C,Van_Aldbda)
SPEDAT(LONGNAME,BSOL,C,Superbee)
SPEDAT(LONGNAME,HSOL,C,Hquick)
SPEDAT(LONGNAME,NSOL,C,Van_Leer_1_(Noll))
SPEDAT(LONGNAME,ZSOL,C,Van_Leer_2_(Zhu))
SPEDAT(LONGNAME,OSOL,C,Ospre)
SPEDAT(LONGNAME,ISOL,C,UMIST)
Here the fourth argument of the SPEDAT command is the said extension, which appears in the RESULT file in the following manner:
 Field Values of ZSOL: VAN_LEER_2_(ZHU:
 IY=  20   9.999E-01   9.997E-01   9.974E-01   9.800E-01   8.148E-01
 
 Field Values of VSOL: VAN_ALDBDA
 IY=  20   9.999E-01   9.996E-01   9.968E-01   9.748E-01   8.088E-01
 
 Field Values of USOL: UPWIND
 IY=  20   9.997E-01   9.956E-01   9.629E-01   8.458E-01   6.284E-01
 
 Field Values of SSOL: SMART
 IY=  20   9.999E-01   9.996E-01   9.975E-01   9.844E-01   8.224E-01
 
 Field Values of QSOL: QUICK
 IY=  20   9.999E-01   9.996E-01   9.975E-01   9.844E-01   8.222E-01
 
 Field Values of OSOL: OSPRE
 IY=  20   9.999E-01   9.996E-01   9.972E-01   9.781E-01   8.132E-01
 
 Field Values of NSOL: VAN_LEER_1_(NOLL:
 IY=  20   1.000E+00   9.997E-01   9.978E-01   9.881E-01   8.158E-01
 
 Field Values of MSOL: MINMOD
 IY=  20   9.999E-01   9.994E-01   9.950E-01   9.615E-01   7.780E-01
 
 Field Values of LSOL: LINEAR_UPWIND
 IY=  20   1.000E+00   9.999E-01   9.998E-01   9.896E-01   8.005E-01
 
 Field Values of KSOL: KOREN
 IY=  20   9.999E-01   9.997E-01   9.975E-01   9.860E-01   8.216E-01
 
 Field Values of ISOL: UMIST
 IY=  20   9.999E-01   9.996E-01   9.967E-01   9.735E-01   7.998E-01
 
 Field Values of HSOL: HQUICK
 IY=  20   9.999E-01   9.996E-01   9.971E-01   9.789E-01   8.234E-01
 
 Field Values of FSOL: FROMM'S_SCHEME
 IY=  20   1.000E+00   9.997E-01   9.978E-01   9.882E-01   8.153E-01
 
 Field Values of CSOL: CDS
 IY=  20   9.999E-01   9.993E-01   9.957E-01   9.780E-01   8.168E-01
 
 Field Values of BSOL: SUPERBEE
 IY=  20   1.000E+00   9.999E-01   9.992E-01   9.945E-01   8.471E-01
 
 Field Values of 3SOL: CUBIC_UPWIND
 IY=  20   9.999E-01   9.997E-01   9.975E-01   9.861E-01   8.203E-01

 Field Values of MSOL: MINMOD
and so on, so rendering the print-out easier to understand

The following points should be noted:

As usual, the data appear in the EARDAT file, which is the intermediary between the SATELLITE and EARTH. In the present case, EARDAT contains the following lines:

 LONGNAME  USOL           CUPWIND
 LONGNAME  CSOL           CCDS
 LONGNAME  QSOL           CQUICK
 LONGNAME  LSOL           CLINEAR_UPWIND
 LONGNAME  3SOL           CCUBIC_UPWIND
 LONGNAME  FSOL           CFROMM'S_SCHEME
 LONGNAME  SSOL           CSMART
 LONGNAME  KSOL           CKOREN
 LONGNAME  MSOL           CMINMOD
 LONGNAME  VSOL           CVAN_ALDBDA
 LONGNAME  BSOL           CSUPERBEE
 LONGNAME  HSOL           CHQUICK
 LONGNAME  NSOL           CVAN_LEER_1_(NOLL:
 LONGNAME  ZSOL           CVAN_LEER_2_(ZHU:
 LONGNAME  OSOL           COSPRE
 LONGNAME  ISOL           CUMIST

Another example is provided by case c110, in which the following statements in the Q1 file:
  
  ** long names for print-out
spedat(longname,epke,c,micro-mixing_rate)
spedat(longname,rady,c,y-direction_flux_sum)
spedat(longname,radz,c,z-direction_flux_sum)
produce the following lines in the RESULT FILE:
  
 
 Field Values of EPKE: MICRO-MIXING_RATE
 IY=  32  1.000E+00  5.682E+02  2.184E+02  6.688E+01  1.064E+01
 
 Field Values of RADY: Y-DIRECTION_FLUX_SUM
 IY=  32  0.000E+00  6.167E+03  6.906E+03  7.448E+03  8.886E+03
 
 Field Values of RADZ: Z-DIRECTION_FLUX_SUM
 IY=  32  0.000E+00  9.671E+03  9.185E+03  8.759E+03  8.922E+03
 
 Field Values of ENUT
 IY=  32  1.000E-20  6.615E-01  7.178E-01  7.769E-01  4.970E+00
It should be remarked although the long-name facility is here illustrated only in connexion with print-out, users can employ it for conveying other information about a variable in their own coding; for they can ascribe whatever meaning they desire to any character, or string of characters, of the long name, and then provide coding in GROUND which reads the name and executes the corrresponding action.

Users who do perform their own coding may care to be reminded that, if the statement debug=t appears in the Q1 file, information about the f-array zero-location is also printed below the field-values line.

Thus, in the case of C110, the print-out would appear as:

 Field Values of EPKE: MICRO-MIXING_RATE
 at L0f= =   17657
 IY=  32  1.000E+00  5.682E+02  2.184E+02  6.688E+01  1.064E+01
 
 Field Values of RADY: Y-DIRECTION_FLUX_SUM
 at L0f= =   17689
 IY=  32  0.000E+00  6.167E+03  6.906E+03  7.448E+03  8.886E+03
 
 Field Values of RADZ: Z-DIRECTION_FLUX_SUM
 at L0f= =   17721
 IY=  32  0.000E+00  9.671E+03  9.185E+03  8.759E+03  8.922E+03
 
 Field Values of ENUT
 at L0f= =   17753
 IY=  32  1.000E-20  6.615E-01  7.178E-01  7.769E-01  4.970E+00

LOOP advanced PIL command

The LOOP.... ENDLOOP construct in PIL

A primitive but powerful looping facility is provided by the LOOP...ENDLOOP construct. The SATELLITE repeatedly executes the statements within the loop until a terminating condition is met. This is provided by a statement such as
IF(logical expression) EXIT which terminates looping when the  logical expression evaluates to TRUE, as in the following example:
 

II=IST
LOOP
MESG(One more time !
+ II=II+1
+ IF (II.GT.IL) EXIT
ENDLOOP

which is equivalent to:
 

DO II=IST,IL
+ MESG(HI THERE)
ENDDO

LOOP constructs can be nested to a maximum depth of 20 and inter- leaved freely with DO loops and other "flow-control" constructs.


LOW

------- Real flag; value= 7.0; group 13 -

LOW....is a PATCH type used for setting sources per unit low ( ie. smaller-z ) area by way of COVAL in group 13. 

LOW-REynolds-number turbulence models

See the PHENC entry: Low-Reynolds-number turbulencs models

Lower limit

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

The minimum value of the current contour range if the RANGE option is on.


LSGx

------ Logical; default= F; group 19 -- -

LSG1,LSG2,LSG3, etc up to LSG100 are spare integers provided for user communication between the SATELLITE and GROUND.

However, CHAM has already made use of several of them by ascribing special meanings to them, as is revealed by inspection of the following extract from the SATGRD common block:

COMMON/LSG/LSG1,LSG2,LSG3,LSG4,LSG5,LSG6,LSG7,LSG8,LSG9,LSG10,
LSG11,LSG12,LSG13,LSG14,LSG15,LSG16,LSG17,LSG18,LSG19,LSG20,
LSG21,LSG22,LSG23,LSG24,LSG25,LSG26,LSG27,LSG28,LSG29,LSG30,
LSG31,LSG32,LSG33,LSG34,LSG35,LSG36,LSG37,LSG38,LSG39,LSG40,
LSG41,LSG42,LSG43,LSG44,LSG45,LSG46,LSG47,LSG48,SYMBFC,GENTR,
LSG51,LSG52,LSG53,LSG54,LSG55,LSG56,LSG57,LSG58,LSG59,ASAP,
LSG61,LSG62,LSG63, GCV, FDFSOL, LASLPA, LASLPB, LCOALA, RESET, PHS2P,
DUDX, DVDX, DWDX, DUDY, DVDY, DWDY, DUDZ, DVDZ, DWDZ, GENK,
ADJEPR, READQ1, PRTSIZ, LCOLOA, LCOLOB, JMPBCK, COMPRS, POTCMP,
POTVEL, JACOB,HOL, QUIK,RADI,RSTM, FGEM,SURF, S2SR, YPLS, STRA

In addition, LSG1, LSG3 and LSG5 are used in connexion with PARSOL.

CHAM has made no use however of the LG(20) array, which is provided for a similar purpose. Users are advised to prefer this to LSG in their own Fortran coding.


LSTEP

------ Integer; default=1; group 2 --- -

LSTEP is a PIL variable set by the user to determine for how many time steps a transient-flow simulation (for which STEADY=F) is to continue.


LSWEEP

---- Integer; default=1; group 15 --- -

LSWEEP is a PIL variable set by the user to determine the maximum number of iterative sweeps through the integration domain are to be performed for each time step.

In a steady calculation, the run is then complete; but in a transient calculation, the computation then progresses to the next time step. LSWEEP is inactive for parabolic calculations ( ie. PARAB=T), for which, by the nature of the calculation , only one solution sweep is required.

Thus, for a steady non-parabolic calculation in which FSWEEP retains its default setting of unity, LSWEEP is the number of solution sweeps to be performed in the run. If FSWEEP has been set to a finite value, for a restarted ( see RESTRT ) run, the number of sweeps to be performed will be LSWEEP-FSWEEP+1 .

For a transient run, FSWEEP will always be unity, LSWEEP is then the number of sweeps to be performed at each time step. Further, if any of the variables are solved whole field (ie. Y entered in the fourth argument of SOLUTN), LSWEEP should never be less than 2, because the effects of the whole-field solver are only felt at the beginning of the second sweep.

In many transient runs it can be helpful to perform more iterative sweeps on the first time step than on subsequent steps. Similarily, if a boundary condition changes, it may be helpful to perform more sweeps on that step.

Inform provides a method doing this, using constructs like:

  save15begin
(store1 of lsweep is 10 with if(tim.gt.10.and.tim.le.20))
  save15end

which would set the number of sweeps to 10 for all steps where the current time (tim) was between 10 and 20 seconds. Outside this period, the number of sweeps would be that assigned to LSWEEP.

The VR-Editor Main Menu, Numerics panel allows up to 15 bands of sweep settings to be made, based on time or timestep number.

For both steady and transient cases, the succession of iterative sweeps will be terminated before LSWEEP is reached, if the total sum of the absolute residuals for all cells in the integration domain becomes less than RESREF(phi) for all phis solved.


LTLS

LTLS is the name of a scalar variable, solution of which is activated by the command DISWAL. From the solution of the equation, two further field variables are deduced, namely the distance to the nearest solid wall, and the distance across the gap between the two nearest solid walls.

See also PHENC entries: DISTANCE from the WALL and LVEL Turbulence Model


LWALL

----- Real flag; value= 22.0; group 13 -

LWALL....is a PATCH type used in group 13 in conjunction with COVAL for representing the sources resulting from a wall at the low faces of the cells identified by PATCH.

See WALL and WALLS for further information


wbs