The material in this tutorial was originally created for delivery as a lecture. It consisted of items of information and advice, interspersed with reproductions of what would appear on the screen if the advice were taken, these being contained between the de-limiter lines:
One such example (with a revealing date) can be seen in section 1 below; but all the rest have been removed (apart from the de-limiters themselves), for three reasons, namely:-
The user is advised to look through this tutorial for points of interest, to return to the interaction with the SATELLITE (by entering Q followed by E) so as to perform the appropriate actions, thereby seeing what would formerly have been placed between the de-limiter lines, and then to return to this tutorial for comments and further suggestions.
>>>: Interactive operation requires that the Q1 file should start with the statement TALK=T. For example, the minimum Q1 file might be created, by means of the computer-system editor, thus:
TALK=T;RUN( 1, 1);VDU=VGACURSR STOP
This prepares the PHOENICS satellite for sending one set of input data to EARTH. The VDU=... command differs from one computer system to another.
>>>: The interactive session can now be started by typing:
whereupon the following message will appear on the screen:-
VVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVV --------------------------------------------------------- CCCC HHH PHOENICS VERSION 1.4, 23 JULY 1987 CCCCCCCC HHHHH (C) COPYRIGHT 1984 CCCCCCC HHHHHHHHHH CONCENTRATION HEAT AND MOMENTUM LTD CCCCCCC HHHHHHHHHHHH ALL RIGHTS RESERVED. CCCCCC HHHHHHHHHHHHH CHAM LTD, BAKERY HOUSE, 40 HIGH ST CCCCCCC HHHHHHHHHHHH WIMBLEDON, LONDON, SW19 5AU CCCCCCC HHHHHHHHHH TEL: 01-947-7651; TELEX: 928517 CCCCCCCC HHHHH FACSIMILE: 01-879-3497 CCCC HHH THE OPTION LEVEL IS -18 ---------------------------------------------------------
TYPE NEXT INSTRUCTION PLEASE, OR ? FOR HELP. ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>>: PHOENICS now waits for instructions, either to set data items or to provide information.
It already has "default" settings of all data items and will disclose these if SEE is typed, as explained in section 5 below.
>>>: The PHOENICS satellite is an "interpreter": it immediately translates instructions typed on the keyboard into settings of data.
>>>: Instructions are accepted at any time in any order, and interpreted at once. If it is desired to re-arrange the order of the given instructions, and then to re-interpret, the EDIT mode can be used, as will be explained in section 8 below. First, however, the "help" facility will be described.
>>>: Typing ? or H elicits the following message on the screen:
>>>: Suggestions are provided for obtaining more detailed help on particular topics. For example, if GROUP is typed, the following message is produced:
As the last two lines imply, there is more to come; pressing the return key continues the message:
The message has described the general arrangement of data input, giving the names of the 24 data-item groups. Just what items are to be set in each group can be found, as the message has explained, by typing GROUP followed by the corresponding number. For example, typing GROUP 1 elicits:
>>>: The "help" file contains information about the data-item and command names understood by PHOENICS. This information be elicited by typing the relevant word. For example, typing TEXT brings the following response to the screen:
Typing REAL brings the longer message:
>>>: These messages have introduced further data-item names, e.g XULAST and COVAL. Information about any of them can be elicited simply by typing the name followed by a question mark, e.g. XULAST ? leads to the message:
>>>: Typing only the name (i.e. without a question mark) will cause the current setting for the name to be displayed, if the name corresponds to a variable which takes a single value. Thus, typing XULAST leads to the message.
And so on. Newcomers to PHOENICS are advised to browse through the "help" file, guided by their interest in the messages they receive.
>>>: If they type a word which is not in the "help" file, the following message will appear:
>>>: The "help" file provides information in response to the typing of some words which are not the names of data items or of commands. Which these are can be learned by typing WORDS, with the result:
This introduction to the "help" file should have enabled the PHOENICS user to understand how he can use it, and what kind of information it contains. It can be explored at the VDU; or it can be inspected in report CHAM TR 200, where it appears as an appendix.
>>>: Attention will now be given to a convenient source of input data for PHOENICS, namely the PHOENICS Input- File Library. **********************************************************
>>>: The command SEELIB, mentioned in the first message from PHOENICS, elicits the following information:
>>>: Then typing SEELIB 1 elicits the following:
>>>: All sections after the first contain the titles of particular input files. Thus, typing the command SEELIB 4 elicits:
>>>: If it is now desired to inspect a particular file, SEELIB followed by the case number brings it to the screen. For example, SEELIB 244 results in:
The above is a typical set of instructions, which, if loaded into the PHOENICS satellite, will provide the data file which tells the EARTH program what it should do.
Beginners are advised to study the instructions, inquiring of the "help" file whenever they encounter a PHOENICS- Input-Language word which they do not fully understand.
>>>: The following points should be noted:-
>>>: There are already hundreds of input files in the library. It is expected that many thousands will soon be available to every PHOENICS user.
>>>: If it is desired to bring a library input file into the instruction stack of the PHOENICS satellite, the LOAD command should be used. Thus the example just inspected can be fetched by the command LOAD(244), with the result:
As the above message indicates, the library entry is now available for the user's inspection or modification.
>>>: There are two modes of inspection available, described in sections 5 and 7 of this document; and there are two modes of modification, described in sections 6 and 7.
Readers who wish to proceed directly to the performance of the flow simulation corresponding to the unmodified entry may wish to skip these sections.
>>>: LOADing the library file caused the PHOENICS satellite to interpret the file. Therefore the data items now have non-default settings, which can be inspected by means of the SEE command, the typing of which leads to the following output to the screen:
If the RETURN key is indeed pressed, information about the setting in the next group is provided, thus:
Alternatively, one may jump to a selected group by typing SEE n, where n is the group number. Thus SEE 5 yields:
>>>: It is not intended in this document to explain the significance of every item appearing in a screen- output example; for the "help" facility, and report CHAM TR 100, can provide full explanations.
Nevertheless the following few words may be helpful
at the present juncture:
>>>: Two further examples will now be shown of what can be SEEn, namely the consequences of SEE 9, which throws light on fluid-property settings, and SEE 15, which reveals some of the solution-control settings. The first, which corresponds to the commands under the GROUP 9 comment in the library file, elicits:
The second, which corresponds to entries below GROUP 15 in the library file, yields:
Data settings of the above groups are among those which it will prove interesting to alter. Attention will now be devoted to describing the first way of making alterations.
>>>: Suppose that it is desired to give the run a new title, e.g. MY FIRST RUN. Then the TEXT command should be used, by typing:
TEXT(MY FIRST RUN)
and SEE 1 will now yield:
Next, suppose that it is desired to increase the fluid density, RHO1, from its default value of 1.0, to, say, 4.967. Then the following should be typed at the keyboard:
whereupon SEE 9 will yield:
>>> Finally, let it be supposed that it is desired to change one of the "residual reference" in proportion to RHO1, by typing:
and to check its efficacy by way of SEE 15. Then the information coming to the screen would be:
which shows that the change has indeed been effected.
>>>: From the last example it will be seen that it is possible to make one change depend upon another. However, care is needed: if the PHOENICS user decided to change RHO1 back again, RESREF(P1) would not be automatically restored at the same time, because all commands are acted upon immediately.
There is a way to ensure that interdependent variables all change in correspondence; but it requires the use the EDITOR mode, which will be described in section 7.
>>>: The instructions which were entered at the keyboard have not been erased as soon as acted upon; instead, they have been added on to the bottom of the instruction stack which at first contained only what was supplied by the LOADing of the library file.
This instruction stack can be viewed by using the built-in editing facilities of the PHOENICS satellite, as will now be illustrated.
>>>: No special command is necessary for entry into the editing mode: its facilities are always on call. However, it may be useful, just before they are employed, to receive a reminder of what they are. This is effected by typing EDITOR, with the following consequential print-out on the screen:
>>>: Some of the commands will now be employed, starting with LB, which results in:
This confirms that the alteration of the RESREF(P1) value is indeed the last command in the instruction stack. Where it lies in relation to the preceding commands can be seen from the "upwards list" shown by the LB command. The prior entries using the TEXT command and setting RHO1 are also shown.
>>>: It should be noted that the editor has added line numbers to the instructions for ease of reference.
>>>: Suppose that the resetting RHO1=1.0 is now made, and followed by L64-68. The bottom of the stack now appears as:
wherefrom it is easily seen that the RESREF(P1) value will correspond with 4.967, not with 1.0.
What was wanted therefore was not the addition of an instruction at the bottom (line 68), but rather the replacement of line 66. This can be effected by typing R66, with the result:
whereupon RHO1=1.0 is typed in. There follows:
again, which means that the editor awaits further editing commands. D68 is appropriate now, because 0 line 68 is redundant; and pressing the return key, on the appearance of the next INSERT EDITS message, signals that the editing is over for the time being.
If now LB is entered,the screen will show:
>>>: If at this stage the PHOENICS user types SEE 15, he will find, possibly to his surprise and disappointment, that RESREF(P1) still equals 4.967E-06. The reason is that, although the instruction stack has been modified, the PHOENICS satellite has not been told to go back to the top and interpret it all over again.
The command which has this effect is LOAD(STACK). If SEE 15 is typed thereafter, RESREF(P1) will at last be found to have the correct value.
>>>: It is especially desirable to use the editor, rather than direct setting of data items, when it is the fineness of the grid which is being changed, for example when NZ is to be increased from 20 to 25. Thus the direct setting NZ=25, followed by SEE 5, will lead to:
This will cause the PHOENICS EARTH run to fail, because NZ has been set to 25 successfully, but still only 20 values of ZFRAC have been provided.
Viewing the instruction stack shows, via LT:
or via L12-15:
VVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVV 12 GROUP 4. Y-direction grid specification 13 GRDPWR(Y,20,0.01,1.0) 14 GROUP 5. Z-direction grid specification 15 GRDPWR(Z,20,0.20,1.0) TYPE NEXT INSTRUCTION PLEASE, OR ? FOR HELP. ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
and via LB:
or via L64-68:
What is needed is D68 to eliminate the last line, and R15, followed by GRDPWR(Z,25,0.20,1.0), RETURN and LOAD(STACK). The result of SEE5 is then:
which is what is required.
>>>: To summarise, instructions can be inserted either directly or after an I (i.e. insert) or R (i.e. replace) command. The direct method is adequate when it is acceptable for the instruction to appear at the bottom of the stack; but the second (i.e. I or R) method should be employed when it is necessary for the instruction to be acted upon before or after certain other instructions.
>>>: When library case 244 is LOADed without modification, the last entry in the instruction stack at line 64 sets the variable NOWIPE to T (for true) as LB reveals:
>>>: The significance of this variable can be ascertained by typing:
which generates the following message on the screen:
>>>: Use of this variable allows successive library cases to build on to a basic problem specification, without the need for typing in many statements which would be the same for the basic case and all its derivatives.
>>>: Consideration of part of the response to entering SEELIB 4 shows that several library cases are dependent on library case 244:
>>>: The dependent cases are 245 to 248 inclusive. However this can be confirmed by typing:
(as indicated in the comment by case 221). The response is:
>>>: The variations made to case 244 are shown by a series of SEELIB commands. Thus typing:
shows the first variation made to case 244:
>>>: A reminder is also issued about how to LOAD this variation, that is to type:
>>>: Typing SEELIB 246 shows the second variation to case 244:
>>>: Entering SEELIB 247 shows the third variation:
>>>: The final variation on the theme of case 244 is shown by typing SEELIB 248:
>>>: Thus case 248 is the same as case 244 with the addition of an internal resriction (case 247) and the introduction of a swirl component to the velocity at inlet.
>>>: In order to LOAD case 248, the correct command is:
which causes the satellite to respond with:
>>>: This message arises because LOAD(244) had previously been entered. Replying with the answer Y causes the instruction stack to be erased. The satellite then gives the message:
>>>: Confirmation that the relevant files have been selected from the library and correctly LOADed can be obtained by using the instruction stack EDITOR.
>>>: Thus L64 followed by an LU command shows the bottom of case 244, and a series of LD commands shows the successive, derivative library cases correctly LOADed into the instruction stack.
>>>: Thus it can be seen that the use of the NOWIPE coupled with the ability to develop from a basic case a series of derivative cases in the PHOENICS input file library, gives a powerful way in which to build up parametric studies.
>>>: When the PHOENICS user is satisfied with the instructions which he has provided, he can terminate the interactive data-input session by typing END.
The following message will then appear on the screen:
The answer Y (i.e. yes) causes the original Q1 file to be over-written by the new set of instructions.
WARNING: Since it is easy to answer Y without due consideration, it is wise to ensure that a back-up copy of every valuable Q1 file is made before the interactive session starts.
The answer Y leads to the following message on the screen:
>>>: Before stopping, the satellite has written a formatted file called EARDAT, which is what will be picked up by EARTH when its execution begins.
>>>: Execution of the EARTH program is initiated by typing:
>>>: Immediately execution begins, the following message appears on the screen:
The first two lines provide information about the GROUND files which are in use, while the third confirms that the EARDAT file has been read.
Of course, the dates will differ according to the version of PHOENICS which is being employed.
>>>: If library case 244 is being run, there follow, after delays corresponding to the execution time needed for each sweep through the integration domain, the messages:
and so on, until the run terminates. Termination is signalled by the message:
>>>: The messages starting TOTAL RESIDUAL are indicators of the extent to which the iterative solution process is converging towards a satisfactory result.
The messages about total residuals, and also the frequency with which they are printed out, are optional, being controlled by the settings of OUTPUT and TSTSWP. The meaning of these names can of course be learned by consultation of "help".
>>>: The final message indicates that, before termin- ation,the values of all dependent variables have been stored in file PHIDA so as to be available for restarts, or for plotting with PHOTON.
PHIDA does not however contain the results that the PHOENICS user wants to look at; the results stored on PHIDA can only be read by EARTH or PHOTON. The results he can read are in the file RESULT, and can be viewed by way of the computer system's editing facility.
For library case 248, the contents of RESULT are as as shown in section 1 of the lecture on PHOENICS output. Discussion of these results will be deferred to that lecture, and to others devoted to boundary conditions and sources.
>>>: There is no necessity to enter insert data interactively; and it is not always convenient to do so.
In non-interactive working, the first statement in the Q1 file must be TALK=F. Then the PHOENICS satellite will simply act upon the instructions in the remainder of the file, without pausing for inputs from the keyboard.
>>>: A Q1 file which would produce the results referred to in section 10 is the following:
>>>: Comments can of course be placed within the file without affecting execution. For example:
>>>: Additional instructions can be added; and they will operate in just the same way as they do during interactive working. Thus:
TALK=F;RUN(1,1) Load case 244 from the input library LOAD(244) Change density RHO1=4.967 Change residual reference of P1 to correspond RESREF(P1)=RESREF(P1)*RHO1 STOP
>>>: All these changes have to be effected by means of the editing facility of the computer system which is being used; for the built-in PHOENICS- satellite editor is available only for inter- active working.
>>>: It will be appreciated that the present document, long though it is, has drawn attention to only a very small proportion of the data-input facilities open to the PHOENICS user.
Even that small proportion can be appreciated by the beginner only if he gains practical experience: and since it is desirable that his earliest experience should be successful, he is here advised to deviate only by small steps from what has been presented above.
Specifically, the beginner is advised:-
Of course, each individual has his own style of learning; and some are bolder (and less prone to discouragement by failures) than those for whom the above advice is designed. There is certainly no necessity to proceed as circumspectly as has been suggested. The main thing is to get started.