In-Form the INput of data via FORMulae

1
In-Formthe INput of data via FORMulae
However hard they try, creators of CFD codes can
never foresee all the processes which their users
will want to simulate for users are humans. They
think of things never thought of before.
But code creators can provide the tools and
instruments which creative thinkers require.
In-Form is a both a constructional tool and an
investigative Instrument, with which PHOENICS was
first equipped in 2001 and which is still being
extensively developed.
It represents the third stage in the process of
enabling users to extend the simulation
capability of PHOENICS in any direction they
choose..
2
In-Forms predecessors

• The previous two stages were

• User programming, (1981) enabling users to add
  Fortran sub-routines written by themselves.
• This facility is still available and used
  but it requires a re-compilable version of
  PHOENICS.

1. PLANT, (1998) which created the Fortran
   automatically upon the basis of formulae
   provided by the user. This, too, necessitates
   having a re-compilable version.

In-Form is also formula-based but no new Fortran
is written nor is any re-compilation needed.
Yes, time must be watched. And In-Form uses less,
both of computers and humans yet it does all
that PLANT could do, and more.
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For what In-Form can be used(Examples will be
supplied later)

• In-Form has very many uses, of which some are

1. creating initial-value distributions
2. introducing non-linear boundary conditions and
sources
3. defining material properties in accordance
with whatever formulae the user wishes
4. computing exact-solution values for comparison
with those which PHOENICS produces
5. defining how objects move in time through
space
6. defining, computing and printing new variables
7. adjusting diffusion, convection and source
terms locally
8. creating transfer and list objects
9. eliciting details of inner workings of
PHOENICS for diagnosis.
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How In-Form works

• 1. In-Form is activated by statements placed
  by the user in the Q1 (input) file in accordance
  with a special syntax.

That is all that the user has to do and even
this labour can be reduced if PRELUDE is employed
(of which more later).
2. The statements are then read by the PHOENICS
Satellite, which writes their equivalents into
the EARDAT file for reading by the PHOENICS
solver ( EARTH).
3. The solver, on first reading EARDAT, rapidly
parses the character strings. It then writes
instructions (to itself) which cause it to
perform the appropriate computations.
No significant computer-time increase has ever
been detected as compared with user- programming
or PLANT processing.
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Examples of the use of In-Form1. the shell-and
tube heat-exchanger
PHOENICS Input-File library case 800 represents a
shell-and-tube heat exchanger, cooling hot engine
oil by cold water.
In-Form is used to calculate the
temperature-dependent properties at each location
for the shell- and tube-side fluids.
The temperatures vary considerably, as shown
here, for the shell-side fluid
and the tube-side fluid
Shell-side fluid (water) flows from left to
right tube-side fluid (oil) from right to left.
The contours for the central plane are shown.
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The shell-and tube heat-exchangerfluid
viscosities

• In-Form is used to compute material properties,
  by extracting formulae from the PHOENICS library.
  Thus, for the kinematic viscosity of water, the
  lines to be copied into the Q1 file are

rho_expressionPOL5(tems,2446.,-20.6741,.11576,-3.
12895e-4,

4.0505E-7,-2.054E-10) emu_expression1.e-7exp((1.
12646-.039638tems) /

(1.-7.29769E-3tems)) (property rho1 is
rho_expression) (property enul is
emu_expression/(rho1))
wherein tems stands for shell-side
temperature, POL5() indicates that In-Form can
handle 5th-order polynomials, exp() indicates
that it can use the exponential
function. (property rho1 sets the density
everywhere, (property enul sets the kinematic
viscosity.
Corresponding lines must be copied in for the
engine oil.
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The shell-and tube heat-exchangerfluid
viscosities and Prandtl numbers.

• The corresponding computed
• fields of (for example) oil viscosity are shown
  here.

Conventional heat-exchanger-design program
presume, by the way, all material properties are
uniform.
Thermal conductivities and specific heats are
similarly computed and from them Prandtl (prs)
and Reynolds (reys) numbers are computed. The
appropriate In-Form statements are (stored var
reys is diamvabs/enul) (stored var prns is
cpsrho1enul/cond)
wherein diam tube diameter, vabslocal absolute
velocity, cpsshell-side specific heat and
condconductivity
This is all the user has to do. PHOENICS reads,
and understands.
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Nusselt numbers deduced from empirical formulae
Where, the heat-transfer specialist should be
asking, will the empirical Nusselt/Reynolds/Prandt
l number formulae appear? We need these for the
heat-transfer coefficients. Answer In the Q1, in
accordance with the users choice.

• Here are examples, for shell- and tube-side
  Nusselt numbers
• (stored var nuss is 0.2reys0.6prns0.33)
• (stored var nust is max(2.0,0.328(reytprnt)0.33
  ))

Please note the In-Form convention indicates
exponentiation so these expressions are of
familiar power-law form but this user has
decided that nust should never be less than 2.0.
Wide place-to-place variations are to be seen
here.
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Shell-side, tube-side and overall heat-transfer
coefficients

• What follows is obvious deduce the coefficients
  from the Nusselt Numbers via further In-Form
  statements, viz

Here are the results
(stored var coes is areadvol
nusscond/diam) (stored var coet
is areadvol
nustcont/diam) (stored var coeu is coes
coet/(coescoet))
shell-side
tube-side
wherein areadvol is area divided by volume,
coes, coet and coeu are the three coefficients,
etc.
overall
Recall all this from Q1 statements alone!
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Assistance with the understanding of print-out
In-Forms longname feature

• Before leaving case 800, note the following
  In-Form statements
• (longname of hs print as shell-side_fluid_enthalpy
  )
• (longname of tems print as shell-side_fluid_temper
  ature)
• (longname of rho1 print as shell-side_fluid_densit
  y)
• (longname of cps print as shell-side_fluid_specifi
  c_heat)

The longnames are what is printed in the RESULT
file so there is no need to remember the
abbreviations used in the Q1.
This is just one of many items which In-Form
provides for the users convenience.
More could be provided. Users suggestions are
welcome.
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In-Form can describe the motion of objects

• A useful feature of PHOENCS
• is MOFOR ( Moving Frames
• of Reference), which permits
• Simulation of relatively
• moving objects and grids.

When MOFOR was first introduced, the motion had
to be described by way of the long, and
not-easy-to-create, MOF file.
Now, however, In-Form can be used for specifying
any motion which obeys mathematical relationships.
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An example library case 766a parabolic
trajectory

• The animated picture shows the velocity vectors
  caused by a body moving in a two-dimensional
  fluid-filled space.

The motion is activated by way of PIL
declarations followed by a few In-Form lines in
the Q1, as follows
SAVE13BEGIN
char(xce,yce,zce,radius,usour,vsour,gravt)
char(vel,times) gravt9.81 vel14.14timestim x
ce0.5timesvel/1.414 zce.05
radius.5 yce0.5timesvel/1.414-0.5gravt
times2
Velocity, time and the gravitational acceleration
9.81 are easily recognised here xce, yce and
zce are coordinates of the body
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An example library case 766a parabolic
trajectory (continued)

• That is not all one still has to define what
  moves, and ensure that its motion is imparted to
  the fluid.

The first is achieved by declaring the existence
of an in-form object of spherical shape, thus
PATCH(PATCH1,CELL,1,NX,1,NY,1,NZ,1,LSTEP) INFOB
at PATCH1 is SPHERE(xce,yce,zce,radius)
with OB_1)
The PATCH arguments allow the sphere to travel
anywhere and the SPHERE function has coordinates
and radius as arguments
The previous slide showed xce linear with time
and yce quadratic. Hence the parabolic trajectory.
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An example library case 766a parabolic
trajectory (continued)
How ensure that its motion is imparted to the
fluid? By way of In-Form source statements, one
for horizontal velocity u1, and the other for
vertical velocity v1.
usour and vsour have already been declared now
is the time to give them meaning, as follows
usourvel/1.414 vsourvel/1.414-gravttimes
(SOURCE of U1 at PATCH1 is usour with
OB_1!FIXV) (SOURCE of V1 at PATCH1 is vsour
with OB_1!FIXV)
This is In-Form speak for wherever object
OB_1 (i.e. the sphere) finds itself in PATCH1,
fix the values of the velocity components of the
fluid to be those of the sphere.
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An example library case 766a parabolic
trajectory (concluded)
But thats so difficult, some may say. Why
cant the VR-Editor enable me to set up the
problem by way of dialogue boxes?
The answer is that it could be programmed to do
so but only for particular trajectories.
But remember Rodins PHOENICS user.
Nevertheless, PHOENICS does now have a user
interface which assists with the input of In-Form
sources, as will now be illustrated. It is called
PRELUDE.
Whatever PHOENICS supplies, its thoughtful users
will think of something else.
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In-Form sources written by PRELUDEa source of
vertical velocity caused by buoyancy
The picture shows what a user might see when
using PRELUDE to set up the simulation of heat
and air flow in a room.
In such circumstances, buoyancy plays an
important role. How is it to be introduced?
An appropriate In-Form source would be
(source of W1 at BUOYANCY is 9.81rho1(tem1-extte
m)/ (273exttem) with volu)
This is In-Form-speak for source of upward
velocity per unit volume is gravitational
acceleration times difference of temperature from
external one divided by absolute temperature.
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In-Form sources written by PRELUDEa source of
vertical velocity caused by buoyancy (concluded)
The PRELUDE user need not remember how to write
that In-Form statement however for he can summon
a buoyancy object, which, when it appears,
already has its W1 source.
Here is part of the screen which appears
and the In-Form expression which is required is
found right here!
The user is permitted to edit the expression if
he wishes then what he writes will be
transferred to the Q1 and onward.
The compatibility of In-Form and PRELUDE is based
on their both using character strings for data
transfer, unlike the VR-Editor.
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Another MOFOR example when the grid accelerates
To simulate flow around accelerating bodies, it
is necessary to make the grid accelerate too.
In-Form makes this easy.

• It must
• make the boundary conditions depend on time and
• Create a body force everywhere.
• Case v207 does this for a sphere, thus

patch(in,low,1,nx,1,ny,1,1,1,lstep) !
Inlet patch. (source of p1 at in is timrho1)
! Flow rate and velocity (source of w1
at in is tim with onlyms) ! increase with
time patch(acel,phasem,1,nx,1,ny,1,nz,1,lstep) !
Body-force patch. (source of w1 at acel is 1.0)
! Z-direction momentum source.
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Case v207The accelerating sphere
Here are velocity vectors and contours at 1, 5
and 10 seconds after the start. The velocity
field quickly develops a steady pattern but of
course the scale increases with time.
This capability of In-Form, like many others, has
not so far been widely exploited, because too
little publicised. Yet it is powerful and simple.
Swerving cars, manouvering ships and (with
foreseen developments) colliding objects can all
be handled with its aid.
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A more unusual examplethe In-Form wave tank
The VR-Editor can handle HVAC with buoyancy
without In-Form so now a more-challenging task
is considered forces on an underwater structure
on the sea bed.
The picture shows one result of the simulation,
in the creation of which In-Form played a large
part.
Its task was to provide initial and boundary
conditions which corresponded to oscillating
potential flow.
The Navier-Stokes equations for the enclosed
space were then solved by PHOENICS.
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The In-Form wave tankthe mathematical foundation

• The ideal wave motion can be calculated from
  the velocity potential, which, on the assumptions
  that the motion is irrotational and the wave
  amplitude small compared with the wave-length,
  obeys the formula
• Pot a cosh(my) cos(mx sigmat)

wherea a measure of the wave
amplitudesigma2 gmtanh(mh)g
gravitational accelerationh mean water depthm
2pi/wave-length
Further, the pressure and the two velocity
components u and v are respectively the
differential coefficients of Pot with respect to
time, the negative-y coordinate and the
negative-x coordinate.
Converting these relations into In-Form-speak
is straightforward.
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The In-Form wave tanksome of the In-Form
statements
The relevant Q1 is Core-Library case 743, from
which a few lines will be displayed in order that
their straightforwardness can be recognised.
Formula for the potential as function of space
and time formaa(cosh(myg))cos(mxg-sigtim)
(stored var pot is form) ! Create the
variable formaa(cosh(myg))cos(mxg-sigtim1)
! tim1tlast/lstep (initial of pot at whole is
form) ! Initialise the field
Formula for the potential-derived u velocity
- d pot/dx form aam(cosh(myg))sin(mxu-sig
tim) ! for all times (stored var upot at whole is
form) ! Create the variable form
aam(cosh(myg))sin(mxu-sigtim1) ! note tim1
(initial of u1 at whole is form) ! Initialise
the field
Its tedious to type but easier than Fortran or
c programming!
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The In-Form wave tanksome other clever tricks
In order to make sure that the pressures and
velocities fit the potential-derived values at
the boundaries, use is made of the (little-used
because little-known) greater-than patches,
i.e.those with names starting gtppot..., gtupot
and gtvpot
Also, not only are the forces on the underwater
obstacle computed, but also its deformations.
Because these are not especially connected with
In-Form, they will not be further discussed here.
However, it is worth remarking that PHOENICS has
many such treasures lying buried in the PHOENICS
ocean!
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In-Form computes exact solutions for comparison
with numerical computations
As well as the deformations of solids, PHOENICS
can also calculate the stresses and strains in
them. (It is untrue that finite-element methods
are necessary for stress-analysis).
Here is an example, chosen because it has a known
analytical solution a rectangular strip with a
circular hole is in tension. Symmetry allows only
one quarter of the strip to be analysed for
economy.
It appears as case s202 in the PHOENICS
Input-File library
In-form enables the numerical and analytical
solutions to be compared.
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In-Form computes exact solutions for comparison
with numerical computation
The exact solution is to be found in I.
Demirdzic, S. Mustaferija "Finite-Volume method
for stress analysis in Complex Domains Int.
J. for numerical methods in engineering", vol.
37, pp 3751-3756 (1994).)
When expressed via In-Form, it
is char(form1,form2) ! Useful declarations to
shorten lines below (STORED VAR R7 IS
SQRT(XG2YG2)) ! Note
SQRT (STORED VAR TET7 IS ATAN(YG/(XG1.e-10)))
! and ATAN form2COS(4TET7))1.5(R0/R7)4
COS(4TET7)) ! and COS (STORED VAR SXTH IS
form1form2 with imatgt100) ! Imatgt10 (STORED
VAR SX-T IS STRX/SXTH-1 with imatgt100) ! 0
solid (STORED defines
and computes new variables (longname of sx-t
print as sx_minus_sxth_divided_by_sxth)
The last line is useful it enables the
fractional error to be printed
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In-Form computes exact solutions for comparison
with numerical computation
Many people turn immediately to graphical display
so as to inspect their results. Here analytical
and numerical x-direction stresses are compared.
Not bad agreement? But the scale maxima are 2.9e4
and 3.26e4 .
Sometimes its better to look closely at numbers,
not colour plots.
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Comparison between analytical solutions
(concluded)
Here then is an extract from the RESULT file
Field Values of SY-T sy_minus_syth_divided_by_sxt
h IY 60 -3.146E-04 1.242E-04 9.213E-04
1.376E-03 8.655E-04 IY 48 -2.133E-02
-1.572E-02 -5.273E-03 3.121E-03 8.614E-03
IY 36 -4.177E-02 -2.867E-02 1.588E-03
1.827E-02 1.782E-02 IY 24
//////////////////////////////////// 4.043E-02
4.374E-02 2.426E-02 IY 12
hole ///////////////////////////////
1.435E-01 3.099E-02 Field Values of SX-T
sx_minus_sxth_divided_by_sxth IY 60
2.302E-02 2.157E-02 1.782E-02 1.334E-02
5.359E-03 IY 48 1.072E-02 7.732E-03
1.691E-03 -2.600E-03 -3.856E-03 IY 36
1.180E-02 1.132E-02 -1.050E-02 -1.467E-02
-6.902E-03 IY 24 ////////////////////////////
////// -4.286E-02 -2.229E-02 -3.843E-03 IY
12 hole ///////////////////////
////// 1.146E-02 6.945E-03 IX 1
13 25 37 49
Appreciable errorsexist near hole edge much
less elsewhere.
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Other uses for In-Form connectedwith
solid-stress analysis
In-Form statements are used in Q1 files to
express stress, load or displacement boundary
conditions, e.g. in case s202
RIGHT U - normal
char(fU3,fU4,TU2,RU2) RU2(R02/(LX2YG2))
TU2ATAN(YG/LX) fU3FX(1-RU2(1.5COS(2T
U2) fU4COS(4TU2))1.5RU22COS(4TU2))
PATCH(RIGHTU,EAST,NX,NX,1,NY,1,1,1,1) (source
of U1 at RIGHTU is COVAL(FIXFLU,fU3fU4))
Of course, this is far too complex for anyone but
a specialist to write therefore the VR-Editor
and PRELUDE are being provided with dialogue
boxes enabling users to insert data in ways
meaningful to them.
PHOENICS is becoming the first SFT (solid-fluid
thermal) code.
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Representing the atmospheric conditions for
wind-farm simulations
When simulating wind farms, it is necessary to
allow for the variation of temperature, pressure
and density with altitude.
In the absence of significant motion and heat
transfer, these properties accord with known
formulae. In-Form provides a convenient means of
inputting these as reference values, tref, pref
and dref, to PHOENICS, thus
(stored var tref is t0(1-zgconst1 )
(stored var pref is p0(1-zgconst1)const2
) (stored var dref is p029/(8314.0t0)(1-zg
const1 ) where zg is altitude and const1 and
const2 are constants depending on ground-level
altitude and temperature
The temperatures, pressures and densities which
PHOENICS computes are then the local deviations
from these quantities.
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Representing the upstream wind-velocity profiles
A related use for In-Form is the specification of
the wind profile. The PHOENICS Commander even
offers a tutorial on this and on many other
topics!
For example a sixth-power polynomial may be used
POL6(arg1,arg2,arg3,arg4,arg5,arg6,arg7,arg8) -
where arg1 may be a constant or a stored/solved
variable, arg2, arg3, arg4, arg5, arg6, arg7 and
arg8 must be constants.
Above is not a sunset but a computed dref
distribution plus hills.
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Domain partitioning exporting and importing
via In-Form

• Domain-partitioning reduces a large calculation
  to a succession of smaller ones
• It is useful for simulation of phenomena
  characterised by a predominant direction of flow,
  e.g when several chemical-plant vessels are
  connected in series.
• A similar situation arises when simulating flow
  over an extensive tract of terrain, e.g. a
  complete city or a wide forest. Partitioning is
  then possible because usually the direction of
  wind varies little from place to place.
• Upstream partitions are simulated first their
  results are dumped as export objects which
  are treated as import objects by the
  next-downstream partitions.
• The computations are carried out successively.

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Using In-Forms transfer objects for import
and export
The idea is simple but implementation has to be
made easy. Therefore Transfer Objects have been
introduced by providing two keywords for In-Form,
namely (EXPORT and (IMPORT
The first causes the PHOENICS solver module,
EARTH, to write a transfer-object file at the end
of its run the second causes EARTH to read such
a file at the start of its run.
Transfer objects can accordingly be created by
placing in the Q1 file In-Form statements such
as (EXPORT in NAME_of_TRANSFER_OBJECT at
PATCH_NAME) or (EXPORT in NAME_of_TRANSFER_OBJECT
at OBJECT_NAME)
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Transfer-object tests, 1
This 2D steady laminar convective and diffusive
flow shows how one gets the same answer whether
one partitions the domain (case B) or does not
(case A)
For this to happen, the flow must be
uni-directional with Reynolds number gtgt 1.
This is Input-File Library case 856 . The
variable is a scalar, viz H1 .
Here is how one of the three export objects is
created PATCH(PAT1,HIGH,1,NX,1,NY,NZ,NZ,1,1) !
States where it is (EXPORT in TROB1 at PAT1)
! Names the file to be used
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Transfer-object tests, 2
This 3D example shows partitioning in two
directions.
It represents a steady atmospheric boundary layer
with a point source of pollutant.
The results with (case B) and without (case A)
partitioning are in close agreement
It is Input-File-Library case 858., in which
TALKTRUN( 1, 5) launches five runs in
succession, one for each sub-domain and a last
one for the whole domain.
35
Transfer-object tests, 3three-dimensional and
transient
This example concerns unsteady spread of a finite
release of pollutant into the atmosphere.
With (lower diagram) and without (higher)
partitioning, the concentration distribution at a
fixed time is much the same
The wind field was constant, but it could have
been allowed to change with time.
This is Input-File Library case 859, in which a
power-law inlet-velocity profile is created by
In-Form thus PATCH(LINLET,LOW,1,NX,1,NY,1,1,1,LST
EP) CONSTRHOINABS(VELZ)/REFHALPHA (SOURCE of
P1 at LINLET is CONSTYGALPHA)
36
Transfer-object tests, 4objects of differing
shape and size
The individual partitions may be more different
from each other, and connected in more complex
ways.

• For example,
• the first might be used to compute the flow and
  heat transfer within, and the output from, a
  computer cabinet
• then the second might comprise a computer room
  with several identical computers within it,

• Another example
• the first might be a room with a smoke-producing
  fire in it,
• the second the space around the building, and
• the third another room into which smoke enters
  through open windows.

Both of these will be illustrated in what follows.
37
Transfer-object tests, 5computers in a room

• Here is the result of computing
• the temperature distribution within, and
• the heat output from,
• a (highly idealised) computer cabinet

Its effects are exported to its environment via
transfer objects at its fan inlets and outlets.
It is Input-File Library case 863, in which some
of the In-Form statements are PATCH(HPAT,HIGH,1,N
X,1,NY,NZ,NZ,1,1) (EXPORT in HIGHTROB at HPAT)
PATCH(LPAT,LOW,1,NX,1,NY,1,1,1,1) (EXPORT in
LOWTROB at LPAT)
38
The cabinet temperature distributionenlarged for
better visibility
39
Several computers in a room
This is the result of the subsequent simulation
of the temperature distribution in a room
containing several identical computers
Their effects are imported via the export
objects of the previous calculation,
This is Input-File Library case 864.,wherein some
of the relevant In-Form statements are (IMPORT
from HIGHTROB at CMP1L) (IMPORT from LOWTROB at
CMP1H) where HIGHTROB and LOWTROB are names of
transfer-object files and CMPIL and CMP1H are
names of placed VR-objects .
40
The computer room enlarged
41
A further example smoke from a room fire
spreads through a building
Here a fire in a room exports its smoke through
open windows.
The fire is treated as steady, which is not
realistic but suffices to show how transfer
objects are used.

• This is Input-File Library case 860., wherein
  VR-object settings convey the export information
  thus
• gt OBJ, NAME, NWIND1
• gt OBJ, POSITION, 6.000E00, 6.000E00, 1.000E00
• gt OBJ, SIZE,
• gt OBJ, EXPORT, wind1.pob

PHOENICS VR-Editor provides menus for
transfer-object setting
42
The flow of smoke around the building
Here the smoke is imported into the
surroundings, which then export some of it to
other rooms in the building.

• This is library case 861.

• Here are some relevant statements fom that file
• gt OBJ, NAME, IMTROB1
• gtOBJ, POSITION, 1.600E01, 2.200E01, 1.000E00
• gt OBJ, IMPORT, wind1.pob

43
Smoke is imported into another room
Here an adjoining room imports smoke through
its open windows
This is library case 862 which, on inspection,
will be found to have the expected import
statements.

• In a more realistic simulation,
• the calculation would have been carried out in a
  time-dependent manner
• all the rooms in the building would have been
  treated in the same way, and
• if two-way interactions were suspected,
  Iterative procedures would have been introduced.

The transfer-object framework is strong enough to
bear all these extra loads..
44
In-Form opens new research doors, e.g. to the
Population Dimension
Other PHOENICS-related presentations have
stressed the population dimension as an important
new direction of CFD developments.
In-Form greatly facilitates entry and
participation.

• The new dimension can take many forms for
  example
• age, or height or pigmentation in humans in one
  country
• temperature, concentration, velocity or droplet
  size in a given cell in a four-dimensional (x, y,
  z, time) CFD computation.

Computed distributions can be represented as
histograms thus
or
45
Built-in population-dimension features of
PHOENICS
PHOENICS has some built-in population-dimension
features, notably its multi-fluid model of
turbulence, especially useful for simulating
chemical-reaction processes.
This calculates both one-dimensional and
two-dimensional histograms such as the following.
But users who have different ideas can express
these via In-Form.
46
Turbulent jet-mixing within a circular pipe
library case 781

• Some history
• PLANT entered PHOENICS in 1998.
• The multi-fluid model (MFM) entered PHOENICS
  during 1995-6.
• Sergey Zhubrin, the initiator of PLANT, used
  PLANT to make his own version of MFM in 1999.
• Nikolay Pavitskiy, the creator of In-Form,
  re-wrote Zhubrins model in terms of In-Form in
  2001.

Library case 781 uses Zhubrins model In-Formised
by Pavitskiy, to simulate turbulent mixing of two
coaxial streams.
The k-epsilon model is used to simulate the
hydrodynamics.
A seventeen-fluid model is used to simulate
mixing, each fluid having a different proportion
of material from the two streams
Conventional single-fluid equations for
time-average concentration and root-mean-square
concentration fluctuations are also solved.
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The results for the conventionally-computed
quantities
Computed values of usual variables are as
expected. Here are the velocity vectors.
Here are longitudinal-velocity contours. The
largest value is on the axis at the entrance.
Time-average concentration contours have similar
shapes.
Root-mean-square fluctuations also present no
surprises
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Results for unconventional quantities
individual-fluid mass fractions
Now for the interesting results individual-fluid
mass fractions. Fluid1 clearly disappears almost
as soon as it enters.
Fluid 17 has a longer life but it is absorbed
into the turbulent jet boundary.
Colliding there with other fluids, it creates
first Fluid 16, and others of course.
Here are the contours of the next-richest in
injected- substance content, Fluid 15.
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Results for conventional quantities computed in
an unconventional way
And so on for all the other intermediate-richness
fluids, which need not however be displayed.
From the complete spectrum (pdf) average and RMS
fluctuations can be directly deduced
Here are the former. The contours are of
identical to those shown above, based on
conventional one-fluid theory.
And here the latter. They are not identical to
those shown earlier. Why not?
Because the g-equation is based on a presumed,
not calculated (by MFM) pdf.
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A calculated pdf at one location in the
turbulent jet
Here is a calculated probability-density function
deduced from knowledge of the individual-fluid
mass fractions, One exists for each computational
cell.
Now that the MFM is available, there is no need
to guess the pdf shape.
Nor need the built-in MFM coding be used In-Form
lets users create own versions.
Question 1. Are the predictions correct?
Answer 1. Only qualitatively for collision-rate
constants are first estimates and experimental
research to refine them is absent.
Question 2. Why is it absent?
Answer 2. Because the existence and ease-of-use
of MFM have been too little known but this can
now change.
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How the 17-fluid model is createdby In-Form
statements
The case-781 Q1 contains all the necessary
statements some of these will now be shown
The conventional RMS fluctuations g is introduced
thus Source term for g PATCH(ISORG,VOLUME,1,NX
,1,NY,1,NZ,1,1) ! Where compute (SOURCE of G at
ISORG is 2.0RHO1EPKE ! How compute
GENG/(2.0RHO1EPKETINY)-G))
where STORED of GENG is 2.8RHO1ENUT

(DFZDFYDFZHDFYN)) EPKEepsilon/k, a
standard PHOENICS turbulence-rate term, DFZ and
DFY and In-Form-calculated concentration
gradients PATCH(PAT1,CELL,1,NX,1,NY,1,NZ-1,1,1)
! Where compute (STORED of DFZ at PAT1 is
((H1,,1-H1)/DZG)2) ! How
Its tedious to disentangle but becomes clear in
the end.
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How collision (i.e. coupling splitting)are
represented by In-Form
Coupling/splitting rates PATCH(iMIX,PHASEM,1,NX
,1,NY,1,NZ,1,1) ! where (SOURCE of F1 at iMIX is
MMCEPKE (F3F5F7F9F11F13F15F17)(0.-F
1) with LINE) ! How
Fluid 1 is never created, only destroyed by
colliding with fluids 3, 5, 7, 9, 11, etc. Not 4,
6, 8 etc. ? Thats Zhubrins concept the
built-in MFM allows more In-Form users decide
for themselves.
Fluid 3 is both created and destroyed. Here is
Zhubrins proposal for its nett source
(SOURCE of F3 at iMIX is 2.MMCEPKE(F2F4F1F
5)- MMCEPKE(F1F17F5F7F9F11F13F
15)F3)
So it is created when fluids 2 and 4 collide
also 1 and 5 and it is destroyed by collisions
with 1, 17, 5, 7, 9, 11, 13 and 15.
Is that reasonable? Each can have his own
opinion. Here we are watching a researcher
exploit the freedom In-Form provides
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More of the same
Long In-Form statements are hard to read but the
PHOENICS Input Language has many ease-of-use
features. Here we see CHARacter declarations
being exploited.
CHAR(SUM1,SUM2) SUM1(F8F10F7F11F6F12F5F13
F4F14F3F15 F2F16F1F17) SUM2(F1F3F5F7F
17F11F13F15) (SOURCE of F9 at iMIX is
2.MMCEPKESUM1-MMCEPKESUM2F9)
Lastly, SUM1 and SUM2 are also used here, where
all the fluid mass fractions are summed for
output purposes
Output calculations SUM116./16.F115./16.F2
14./16.F313./16.F4 SUM212./16.F511./16.F61
0./16.F79./16.F88./16.F9 (STORED of CAV is
SUM1SUM2 with IF(ISWEEP.EQ.LSWEEP))
54
What have we learned from the study of case 781?
That PHOENICS is capacious enough to enable users
to introduce new stored or solved-for variables
at will.
That In-Form then allows them to prescribe their
values, their sources and their boundary
conditions according to arbitrary formulae.
That these are precisely the facilities which are
needed to allow users to undertake researches in
the Population Dimension of modern CFD.
That unprecedented new CFD simulations can then
be swiftly carried out without creation of any
new Fortran, C or C codiing whatever.
The facilities are of course available for any
other, even not-yet-thought-of novel
investigations. PHOENICS is the Thinkers code.
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When the fluids do not all have the same density
Multi-fluid models throw much light on
chemically-reacting flows then the distinct
fluids have differing compositions, temperatures
and densities. The latter effect will now be
explored.
A single In-Form line added to the case-581 Q1
allows this (property rho1 is (f1f17)1.0(1.-f1
-f17)0.1) which gives all the created-by-collisio
n fluids the density 0.1, so as to represent
crudely the effect of combustion which can be
done in a few seconds, whereas a few minutes
would be needed to represent it realistically .
In a few more seconds one has performed the run
and can inspect the results. Here is the pdf for
the same position as before. It is of course
different.
56
More results when density of new-created fluids
has been reduced to 0.1
Here is the resulting distribution of
mixture-average density
here is the consequent velocity-vector diagram,
which is of course different from before.
and here is the resulting distribution of
fluid-16 mass fraction, also different.
Having thus very quickly established that results
are qualitatively as expected, it is worth
spending the few minutes required for realism.
It is the existence of the hundreds of
input-file-library cases as starting points,
which allows such swift progress to be made
57
Further possible directions of investigation
opened up by In-Form
Because fluids of different density respond
differently to pressure gradient, relative
velocities arise, expressible via In-Form, which
influence collision rate.
Different temperatures and compositions lead to
different reaction rates, e.g. of NOX or smoke
formation. Non-linearity invalidates conventional
single-fluid computations, also two-fluid models
such as eddy-break-up and eddy-dissipation.
How many fluids are needed for accuracy? That
depends on the particular problem,
In-Form permits fluid number to be easily varied,
so allowing population-grid-refinement studies.
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Further possible directions of investigation
opened up by In-Form
Radiation fluxes vary as T4 and with
composition. Therefore hazards from gas
explosions require multi-fluid analysis for their
prediction. In-Form facilitates this.
The built-in MFM of PHOENICS allows 2D
populations (eg fuel-air ratio and reactedness.
An In-Form-based alternative would be simple to
create. Remember no coding is needed. Any
user can do it.
In short, the possibilities are endless
59
User-support in respect of In-Forma warning
In-Form is so powerful that CHAM has had to
introduce a change of policy whereas much user
support has been provided free of charge, this is
not possible when In-Form has been extensively
exploited.

Many users have enthusiastically adopted In-Form
as their means of creating process simulations of
unprecedented nature and complexity and
sometimes they have obtained unexpected, puzzling
and even undesired results.


Understandably, they ask why? or did I do
something wrong? CHAMs user-support team would
like to assist them. but this time-consuming
assistance needs to be paid for.
Of course, if finally the results can be
attributed to a defect in the software or
documentation, the obligation to pay is waived.
But such defects are nowadays rarely found.
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