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The main features of PHOENICS

PHOENICS is a general-purpose CFD software package, created and marketed by CHAM.

• What PHOENICS does
• How the problem is defined
• How PHOENICS makes the predictions
• How the results are displayed
• Hardware on which PHOENICS runs
• Customisation of PHOENICS
• Learning to use PHOENICS

1. problem definition, in which the user prescribes the situation to be simulated and the questions to which he wants the answers;
2. simulation, by means of computation, of what the laws of science indicate will probably take place in the prescribed circumstances;
3. presentation of the results of the computation, by way of graphical displays, tables of numbers, and other means.

The three modules of PHOENICS are called:-

1. SATELLITE;
2. EARTH; and,
3. PHOTON.

and here to learn about the more varied environments and satellites of PHOENICS.

How the problem is defined.

Problem definition normally involves making statements about:

• geometry, ie shapes, sizes and positions of objects and intervening spaces;
• materials, ie thermodynamic, transport and other properties of the fluids and solids involved;
• processes, for example:
  • whether the materials are inert or reactive;
  • whether turbulence is to be simulated and if so by what model;
  • whether temperatures are to be computed in both fluids and solids; and
  • whether stresses in solids are to be computed;
• grid, ie the manner and fineness of the sub-division of space and time, ie what is called the "discretization"; and
• other numerical (ie non-physical) parameters affecting the speed, accuracy and economy of the simulation.

• problem definition can be carried out in a variety of ways, selected by the user according to his experience or preference;

• thus, engineers who use CAD packages can export the corresponding files directly to PHOENICS-VR (ie Virtual Reality);

• VR, and other interactive input procedures of PHOENICS, create as a record a "command file", called Q1, which experienced users of PHOENICS can modify by editing, thus sparing themselves the tedium (as they sometimes see it) of further interactive sessions;

• the "PLANT" feature of PHOENICS allows the property laws of new materials to be supplied by the writing of formulae into the command file; and

• hundreds of quality-assured command files are supplied with the standard PHOENICS software in a set of easily accessible libraries, so that the user rarely has to start from scratch.

PIL is a directly-interpreted language, requiring no compilation; and its capabilities include:

• direct assignment, as in:
  • NX=10;
  • CARTES=F (ie false);
  • PI=3.1416
• interrogation, as in:
  • NX?
  • CARTES?
  which print the values of the referenced variables
• arithmetic commands, as in: NX=2*NY
• conditional settings, as in:
  • IF(NX.EQ.10) THEN
  • CARTES=F
  • ENDIF
• DO loops, as in:
  • DO II=1,3
  • MESG(Three cheers! HURRAH!
  • ENDDO
• INCLUDE commands, as in: INCL(file name
• LOAD commands, as in:L(library case number
• numerous other facilities for setting grids, boundary and initial conditions, material properties, output needs and other data.

PHOENICS simulates the prescribed physical phenomena by:-

• expressing the relevant laws of physics and chemistry, and the "models" which supplement them, in the form of equations linking the values of pressure, temperature, concentration, etc which prevail at clusters of points distributed through space and time;
• locating these point-clusters (which constitute the computational grid) sufficiently close to each other to represent adequately the continuity of actual objects and fluids;
• solving the equations by systematic, iterative, error-reduction methods, the progress of which is made visible on the VDU screen;
• enabling the computations to be interrupted, and the controlling settings to be modified, as the user desires;
• terminating when the errors have been sufficently reduced.

Special features relating to how PHOENICS makes the predictions are:

• PHOENICS can handle a wider range of physical processes, and is equipped with a more extensive range of physical models, than any of its competitors.
• The ways in which these physical processes are represented in the computer language, Fortran, are visible and accessible to users, and not hidden as in most other codes. The relevant coding, called GROUND, constitutes more than fifty percent of the EARTH module.
• This open-source coding is written in a well-annotated easy-to-follow manner, in order that users can, if they wish:
  • understand,
  • decide whether CHAM's provision meets their needs, and
  • either modify it or add coding of their own.
• For users who are not confident of their ability to do this, CHAM has provided the PLANT option, which reduces the user's duties to entering the required formulae into the command file.
• Unlike those other CFD codes which cope with geometrical complexity by the use of "unstructured grids", PHOENICS retains the computational economy of the more-orderly "structured grids", while utilising "multi-block", "fine-grid-embedding" and PARSOL, ie "cut-cell", techniques for handling geometric complexity.
• A related and unique feature is the MOVSOL, feature, which makes it easy, economical and accurate to allow curvilinear solids to move relative to each other across cartesian grids.
• PHOENICS possesses a unique EXPERT feature, which automatically optimises the numerical parameters as the computation proceeds.
• PHOENICS also employs an economical and unique-to-it "parabolic" grid when flow is of the very common "boundary-layer" character.
• The PHOENICS grid has lent itself particularly well to "domain-decomposition", which is what is needed for parallel computers.

It has its own stand-alone graphics package called PHOTON; and it can also export results to such third-party packages as TECPLOT, AVS, and FEMVIEW.

Unique to PHOENICS is its ability to take the results of its flow predictions back into the same Virtual Reality environment as is used for setting up the problem at the start.

This facilitates understanding by the user; and it also affords a means of conveying the significance of the flow-simulation operation to interested but non-technical persons, eg. high-level managers.

Of course, numerical results are also provided, in the RESULT file. This, when the appropriate commands are placed in the Q1 file, can provide either sparse or voluminous information.

PHOENICS runs satisfactorily, with full functionality, on all hardware platforms, from personal computers, through UNIX work-stations, to single- or multi-processor super-computers.

On personal computers, the operating systems may be: DOS, Windows-95, WINDOWS-NT, or LINUX.

The parallel version of PHOENICS has been successfully ported to all the most- frequently-encountered shared-memory parallel machines, as well as to those employing distributed memory.

Of especial interest, because of the high power/cost ratio, is the use of PHOENICS on net-worked clusters of personal computers, under either the LINUX or Windows-NT operating systems.

So far as is known from published information, PHOENICS is the only general- or special-purpose CFD code to be capable of working in this way at the present time.

(a) Customization by addition.

Rich though it is in flow-simulation capability, users of PHOENICS often wish to apply the code to tasks requiring additional features.

PHOENICS has therefore, from the start, been given an open-ness of structure and access which has allowed users to add Fortran modules of their own. This is represented by the GROUND feature (see above).

The PLANT facility carries customizability to new levels of convenience (see below).

Many examples of user-generated GROUND coding are to be found in, and can be copied from the pages of the regularly-published PHOENICS Journal.

Although some other CFD codes have recently been equipped with some "user- programmable sub-routines", none, it has been asserted by PHOENICS users who have examined other codes, afford such customization power as PHOENICS does; and the majority provide none at all.

(b) Customization by subtraction.

Many users require not greater power but less; for their range of applications is narrow; and they do not wish to be distracted by, or to pay for, what they will never use.

The structure of PHOENICS itself, and of its pricing, are compatible with their desires; for many of the features of PHOENICS are optional; and, if they are struck from the list at purchasing time, the price of the software licence is correspondingly reduced. Options which can be dispensed with in his way are:

• Two-phase (IPSA);
• Body-fitted coordinates;
• Solid-stress and -strain;
• Multiblock & fine-grid-embedding;
• GENTRA particle tracking;
• PLANT;
• Multi-phase flow;
• Numerical algorithms;
• Chemical reactions;
• Radiation;
• Conventional turbulence models;
• Multi-fluid models.

(c) Customization by BOTH subtraction and addition.

The largest number of users may require customization of both kinds; for the narrowness of their application sector may render many of the physical-simulation capablities of PHOENICS unnecessary; but they probably have special requirements in respect of:

• geometrical shapes of objects to be imported;
• materials, and their flow-influencing properties;
• initial conditions, for example sudden local heat input;
• output requirements, for example the stresses at critical locations;
• display requirements, for example to export the result and make then visible in AutoCad;
• automatic selection of optimal solution-control settings;
• nomenclature.

In order to make these special-purpose programs available to users who need CFD only occasionally, CHAM is creating a remote-computing facility via the Internet.

The most important sources of information are listed below.

An extensive set of on-line documentation, which includes:

• lectures;
• tutorials;
• an Encyclopaedia; and
• an Applications Album.