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  • is adopted it is usual to prescribe a uniform value for the whole fluid field A suitable value is of the order of 0 005 typical velocity typical cross stream distance In PHOENICS setting ENUT to the required value in the Q1 file is all that it is necessary to do It should be noted that the value whch is set is the kinematic viscosity This is automatically multiplied by

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  • as for the mean value of the relevant fluid attribute Subsequently Lockwood and Naguib 1975 made the clipped Gaussian presumption they were followed by others including Kent and Bilger 1976 Kolbe and Kollmann 1980 Rhodes et al 1974 and Gonzalez and Borghi 1991 Clipped Gaussian and beta function presumptions are popular b Doubts Despite their popularity presumed pdf approaches lack physical plausibility That SOME account for the non uniformity of a turbulent mixture must be taken is sure but to presume without evidence that one pdf shape is preferable to another is dangerous Use of the multi fluid model has shown that a wide range of shapes can arise even within the same flame MFM has also been shown that the differing shapes have significant effects on quantities of interest to engineers for example the yields of desired nd undesired reaction products When the presumed shape is mathematically complex some rather time consuming computations can ensue Therefore if the presumed pdf approach is to be used at all simple shapes are to be preferred c Activation in PHOENICS The only presumed pdf model which is supplied with PHOENICS is the two spike version which forms part of the SCRS coding

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  • RQ1.HTM
    following lines at any point within the Q1 file NUGRBEGIN LOG1 T INT1 10 REL1 1 2E3 CHA1 CHAM NUGREND The number of blanks between entries on a line has no significance but the first two spaces on the line should always be left blank Lower case characters may be used they will be converted to upper case by the SATELLITE For method 1 at the point in the GROUND coding where it is desired to read the data the following FORTRAN lines should be inserted LOGICAL LOG1 CHARACTER 4 CHA1 CALL RQ1L NUGR LOG1 LOG1 CALL RQ1I NUGR INT1 INT1 CALL RQ1R NUGR REL1 REL1 CALL RQ1C NUGR CHA1 CHA1 only upper case characters being allowed between the marks Method 2 provides a more economical way to set information in Q1 files and to read it in by FORTRAN coding Moreover as well as being able to read lines such as are shown above it can interpret lines with several data settings such as the following NUGRBEGIN LOG1 T INT1 10 REL1 1 2E3 CHA1 CHAM NUGREND To process these lines the user needs to insert Fortran coding such as the following LOGICAL LOG1 RQ1LG RQ1IN RQ1RL RQ1CH RQ1OK CHARACTER 4 CHA1 10 IF RQ1BG NUGRBEGIN THEN IF NOT RQ1EN NUGREND THEN RQ1OK RQ1LG 1 LOG1 LOG1 RQ1OK RQ1IN 3 INT1 INT1 RQ1OK RQ1RL 5 REL1 REL1 RQ1OK RQ1CH 7 CHA1 CHA1 GO TO 10 ENDIF ENDIF Note that the first argument of each RQ1 subroutines designates the position of the keyname say LOG1 or CHA1 in the line of the Q1 file This line is read in by the RQ1EN subroutine and thereafter processed by the RQ1LG RQ1IN RQ1RL or RQ1CH subroutine Lines containing single settings such as are appropriate to the first method can also be used

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  • Relational Input Tutorial 1 - Part 1
    default case this file comprises 4 more sub cases with additional features differing by their attribute being the case number caseno The next line in this section declares caseno to be integer and this is quite obvious as this variable is introduced only to distinguish one sub case from another The next line is simply a text that explains what is to follow i e what messages are to appear on the screen Next are several mesg commands used to transmit text after an opening round bracket to the screen during interactive session Introducion of this information to the Q1 file enables the user easily orient himself among all four sub cases Each sub case is described here by two successive mesg commands For the basic sub case with caseno 0 these are mesg caseno 0 mesg basic case with minimum settings These two commands will result in the following on the screen caseno 0 basic case with minimum settings What the possibilities are is clear from the picture you will see when you run this case Now follows the last mesg command that is slightly different from the previous ones viz mesgm caseno equals caseno OK If not enter required value Its only difference from the previous is that it puts blank lines above and below the line which follows as you can see from the above picture To read more about mesg commands click here The following four lines are comments which explain how the user s choice of a specific case number is first set by the user and then transmitted to the SATELLITE The user s task is either to type a specific sub case number from 2 to 4 and then press ENTER on the keyboard or if he prefers the basic case to deal with caseno 0 simply press ENTER It is the readvdu command which enables reading of keyboard input i e it enables the user to respond via the keyboard to requests from the SATELLITE about specific sub case that he has selected Parameters in round brackets caseno int caseno denote the following caseno a variable to be introduced int its type i e integer caseno the value of this variable that has been set earlier by the user via keyboard input Find more about readvdu command here The following marker save1end shows that the protected part of GROUP 1 ends here 2 4 The next part of the file is the one for GROUP 3 and as its title shows it deals with specification of the X direction grid creating a uniform one for the calculation domain This part of the Q1 file is also protected by the markers save3begin and save3end The first command within these markers is a conditional command of the type if logical expression then statement1 endif The logical expression in round brackets specifies the condition on which the next statement i e statement1 should be fulfilled For the present case this condition is caseno ge 0 meaning that if the variable caseno is greater than or equals to zero i e it covers all the cases given then the next statements should be fulfilled The statement NX 100 as the comment explains divides the x dimension of the slab into 100 elements i e there are 100 grid cells in the X direction XULAST 0 1 means that the thickness of the slab is set to 0 1 m Then comes the GRDPWR command which creates grids It contains four arguments in brackets namely X NX XULAST 1 0 first argument X indicates that the dimension X is in question second argument NX indicates the number of elements or grid cells of this dimension third argument XULAST is the maximum extent of the dimension X i e the thickness of the slab and the fourth argument 1 0 as the comment explains sets the exponent in the power law distribution equal to 1 0 i e creates a uniform grid For more details you may consult Encyclopaedia by clicking here The protected part for GROUP 3 ends here as the save3end marker shows 2 5 We now deal with GROUP 7 which answers for storing solving and naming variables This part is also protected by markers save7begin and save7end The next line is SOLVE TEM1 the command stating which are the solved for variables in future simulation The only variable in brackets is TEM1 which means that the aim of our simulation is to calculate temperature distributions for the heated steel slab You may find more in Encyclopaedia about this command if you click here Then come two store commands stating which auxiliary variables are required to run this simulation but which are not solved STORE PRPS specifies that the material identifying variable PRPS is required As will be seen below assigning its value to steel or to copper which are integers equal to 111 and 103 respectively ensures that the correct values for thermal conductivity are extracted from the file called PROPS which may be seen by clicking here How material properties are introduced into PHOENICS calculations is too large a subject to be discussed in this tutorial but the full account in the PHOENICS Encyclopaedia can be consulted by clicking here STORE KOND brings in the thermal conductivity which is the only property influencing the process which is being simulated You may read more about store command by clicking here The next line endif declares that this is the end of the if command for the condition caseno ge 0 The next part of the Q1 file is valid for the condition if caseno gt 0 i e for all the cases except one with caseno 0 Its purpose is to enable the accuracy of the numerical calculations to be checked by comparison with the known analytical solution Because this part of the file contains explanatory commments it is included here verbatim as follows CHAR FORMULA Declare the character variable FORMULA and set it to the temperature calculated by PHOENICS viz TEM1 divided by the theoretical temperature namely that described by the following FORMULA TEM1 0 5 1 E3 XG 005 XULAST 995 XULAST XG KOND where 0 5 is a constant in the theoretical expression for the parabolic profile 1 E3 is the volumetric heat input xg x value of any grid point 005 xulast xg of first grid point 995 xulast xg of last grid point KOND is the thermal conductivity of the material STORED var RAT is FORMULA Calculates the temperature ratio The comments explain that FORMULA is being used so as to determine the accuracy of the simulation It contains the parabolic temperature distribution which would be derived by solving the differential equation governing one dimensional heat conduction in a uniform property solid XULAST introduced between colons signifies that the numerical value of this variable i e 0 1 should be used in the earlier expression STORED var RAT is FORMULA is the command which assigns the numerical value of the variable FORMULA to another variable called RAT Next line endif shows that here ends the conditional statement for the sub case caseno gt 0 and the following marker save7end confirms the end of the protected part for GROUP 7 2 6 Now comes GROUP 11 connected with initialization of variables or porosity fields It is the part of Q1 where initial values of variables are supplied You may consult Encylcopaedia here to learn more about it This part is also protected by the corresponding markers save11begin and save11end The first command in this section FIINIT PRPS STEEL specifies the properties of which material should be taken from the whole array of properties in the PRPS file We need properties of steel for this simulation However the next conditional command if caseno gt 3 warns that for the sub case 4 it is necessary to replace steel by copper as the next command instructs FIINIT PRPS COPPER That is the end of the conditional statement endif and of the protected part too save11end 2 7 Next part is for GROUP 13 dealing with boundary conditions and special sources Here boundary and internal conditions as sources and sinks are treated For more details click here This part is protected by the markers save13begin and save13end The first command within these markers is the PATCH minXface WEST 1 1 1 1 1 1 1 1 command that locates the low x face its 10 arguments being as follows minXface patch name up to 8 characters long WEST specifies that WEST direction coincides with X axys starting from smaller X section The last eight arguments are normally integers which locate the patch by reference to the computational grid namely 1 first cell in x direction nx last cell in x direction that is also 1 as we are setting the low x face 1 first cell in y direction ny last cell in y direction being 1 for the low x face 1 first cell in z direction nz last cell in z direction being 1 for the low x face 1 first time step 1 last time step being also 1 as only one sweep or one iteration is to be made Next PATCH maxXface WEST NX NX 1 1 1 1 1 1 command is used to locate the high x face its arguments being practically similar to those of the first PATCH command except for the last cell in x direction And it was assigned to be NX 100 For more details about PATCH command click here Then come two COVAL commands which are used to introduce boundary conditions for our case i e COVAL minXface TEM1 FIXVAL 0 0 and COVAL maxXface TEM1 FIXVAL 0 0 The arguments in round brackets indicate the following minXface and maxXface are the names of the patches located on the corresponding faces to which the COVAL commands refer TEM1 is the solved for variable in question FIXVAL means fix the value of this variable and the last argument 0 0 indicates that the ends first and last faces in x direction should be kept at a constant zero temperature as the explanatory comments which follow the exclamation mark assert To learn more about this command click here There follows the command which introduces the patch called HEATER PATCH HEATER volume 1 nx 1 1 1 1 1 1 The arguments 1 nx specify that the volumetric heat flux extends from low x to high What ensures that it is a volumetric flux is the word volume which appears as the second argument of the PATCH command this specifies the type of the patch A description of what other possible types may be invoked is to be found by clicking here The types WEST and EAST it may have been noticed were used for the slab face patches The type name is not case sensitive It is followed by COVAL HEATER TEM1 FIXFLU 1 e3 that is another COVAL command to fix the heat flux at a constant value of 1kW m 3 Next is the conditional statement if caseno gt 2 giving new instructions for sub cases with the variable caseno exceeding 2 These are the following First two real variables are declared REAL THICK HEATINPT which denote the slab thickness and the heat input Then already familiar numerical values are assigned to these parameters i e THICK 0 1 m and HEATINPT 1 0E3 kW m 3 The command creating the grid is therefore rewritten in the following way GRDPWR X NX THICK 1 0 in view that the slab thickness is now designated as THICK And the same COVAL command fixing the heat input is now as follows COVAL HEATER TEM1 FIXFLU HEATINPT The next line with endif indicates the end of the conditional statement and the very last line in this section save13end marks the end of this protected part 2 8 The last part of the Q1 file is for GROUP 23 which allows variable field print out plotting and tabulation of spot values and residuals Consult Encyclopaedia for more details This part is also protected by the markers save23begin and save23end It starts with with the conditional statement if caseno gt 1 and is valid for the sub cases with the variable caseno starting with 2 These are the sub cases for which the temperature profile will be plotted in the result file as the comment explains Next comes the PATCH command called TEM1PLOT wherein the word PROFIL indicates that a profile is to be plotted along the whole range of the slab thickness i e from the first face to the very last NX PATCH TEM1PLOT PROFIL 1 NX 1 1 1 1 1 1 all other parameters being unchanged i e one cell only in Y and Z directions and one time step considered TEM1PLOT is merely a name which the user has chosen for the patch any other name can be used provided that the same one is used in the following PLOT command You may find more about plotting profiles by clicking here The second argument of the next command PLOT TEM1PLOT TEM1 0 0 0 0 specifies that the variable to be plotted is TEM1 The third and fourth arguments of the COVAL command are provided to enable the user to select first the minimum and then the maximum values of the ordinate scale When they are both left as zeroes the user is indicating that he wishes to make no specifications In effect he is saying to PHOENICS You choose PHOENICS then chooses such a scaling procedure as causes the lowest point of the curve to lie on the bottom line and the highest point to lie on the top line of the rectangular frame of the picture The last statement in this part is ORSIZ 0 2 This quantity is described in the Encyclopaedia entry as being the height of the frame enclosing the PROFIL plot and having a default value of 0 4 which gives 20 printed lines Evidently the writer of the Q1 preferred a smaller diagram choosing 0 2 for ORSIZ and so printing only 10 lines as will be seen below He was apparently content with its horizontal dimensions for he did not make a setting for the corresponding variable ABSIZ which has a default value of 0 5 giving a 50 column wide plot frame Next line with endif shows the end of the conditional statement when the variable caseno is greater than 1 Next is the statement LIBREF 163 that denotes the reference number of the Input Library case this being as has been stated above 163 Then comes the marker save23end indicating the end of the protected part for GROUP 23 The last statement STOP indicates the end of a particular run For more details press here 3 Some conclusions about the file structure Having discussed every part of the Q1 file it is now possible to give summarization as to its structure It has been already mentioned above that the Q1 under consideration describes the simulation problem with the help of one basic case and four sub cases differing in the variable caseno It may be useful to remind the user what these are caseno 0 This is the basic case with minimum settings caseno 1 The basic case that allows a comparison with exact solution caseno 2 Similar to the previous case the temperature profile along the slab thickness is plotted here caseno 3 Similar to the previous case two real variables THICK and HEATINPT are declared and set here caseno 4 The metal of the slab is here changed from steel to copper 4 Making a simulation In this section we shall make a simulation for the same problem running the basic case andfour sub cases You may make these runs in any possible way you prefer A convenient way of doing so is via the PHOENICS Commander s input file library feature We suggest that first of all you create five separate folders for each run where the results of each simulation will be stored After that do the following 4 1 Sub case with caseno 0 Open the PHOENICS Commander Click the Input File Library button in the top row Click the set work dir button in the top row then click select and browse for the working directory you have created for caseno 0 Click the choose by case number button on the left insert the case number 163 in the case number box and click on the Load it button Your actions will result in the following picture From the list of commands choose Run the case You will see the already familiar screen Click ENTER to load the basic case with minimum settings After some short time the simulation will be made You might have to move the PHOENICS Commander window by the title bar to get the picture like this one Load the result file into the Commander editor clicking the tab Result file in the bottom row Browse the file to the bottom where Field Values are given These values are as follows Field values of KOND are represented by a constant of 4 300E 01 i e the thermal conductivity of this material steel being 43 watts m degC for each face IX here equal to 1 21 41 61 and 81 is a number of a specific face Field Values of PRPS are also represented by a constant of 1 110E 02 this being a number of steel in the database of materials properties collected in the PRPS file And at last Field Values of TEM1 represent acually the solution of the problem under consideration as these are temperature values in specific faces expressed in degrees Celsius Pay attention to the temperature value at the first face IX 1 being 2 500E 09 that is very close to the desired zero value

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  • Relational Input Tutorial 1 - Part 2
    result file then shows to IX 1 value of RAT to be 1 002 which is satisfactory Let us now increase NX further to 10000 by adding the following lines to the bottom of the q1 file NX 10000 GRDPWR X NX XULAST 1 0 To create a uniform grid PATCH minXface WWALL 1 1 1 1 1 1 1 1 to locate the low x face PATCH maxXface EWALL NX NX 1 1 1 1 1 1 to locate the high x face PATCH HEATER volume 1 nx 1 1 1 1 1 1 to show that the volumetric You will see an error message if you try to run EARTH Go no further The subject lies beyond the scope of this tutorial Do not forget to delete the last changes introduced On the basis of the following analysis it is possible make the following conclusion A reasonable setting of of the number of cells is of great importance as it influences the simulation results too coarse a grid introduces a great error and too fine cannot be processed by the solver so the number of cells should always be necessary and sufficient to provide satisfactory accuracy without increasing the time of simulation too much Usually it is not possible to say in advance what grid would be sufficient unlike in this case when the accurate solution is available That is the reason why in most cases it is necessary to make several runs with different cell numbers in the calculation grid Step 11 Setting the thermal conductivity The thermal conductivity of most materials varies with temperature It is therefore useful to investigate the effect of such variations on the temperature distribution produced by a given heat flux Before explaining how to do this it will be useful to describe the various ways of introducing CONSTANT conductivities First let us revert to the earlier grid as follows NX 100 GRDPWR X NX XULAST 1 0 To create a uniform grid IXPRL NX NXPRIN NX 5 and run the executable The results should be as follows Step 12 How not to set the conductivity Now we abandon the use of the PROPS file by nullifying the above STORE PRPS by way of the command SOLUTN PRPS N N N N N N and supposing it to be reasonable to do so insert the value of KOND to be used at every point by way of the initial value statement FIINIT KOND 43 0 Both these statements should like all others in this tutorial be placed just above the save25end statement at the bottom of your q1 file The last seven lines of this file should now look like this NX 100 GRDPWR X NX XULAST 1 0 To create a uniform grid IXPRL NX NXPRIN NX 5 SOLUTN PRPS N N N N N N FIINIT KOND 43 0 save25end Running the case then shows that the temperatures are much higher than before and that KOND is being reported as 1 0E 05 i e much lower that the one which we attempted to impose RAT is still unity or very close to it because the formula has used the low value of KOND in both cases i e for simulated temperature and accurate one What has happened is that although PHOENICS will have accepted 43 0 as its initial value of KOND it did not receive the instruction to use that value which was formerly implicit in the setting of the value of PRPS to steel Having no other instructions PHOENICS therefore reverted to its default practice which involves deducing thermal conductivity from the Prandtl Number The relevant default settings are PRNDTL TEM1 1 0 the Prandtl number RHO1 1 0 the density CP1 1 0 the specific heat ENUL 1 0E 05 the kinematic viscosity Since the Prandtl Number is defined as ENUL RHO1 CP1 KOND it is not surprising that KOND has been reported as 1 0E 05 A remark to critics We are here studying how PHOENICS does behave not how a newcomer might reasonably believe that it should behave Therefore the only conclusion we can make here will be this one It is not possible to set the conductivity in the most obvious way but When at Rome do as the Romans do Although most obvious things are not always realized we shall further show what exactly you can do in the land of PHOENICS Step 13 A successful way of setting the conductivity If a conductivity of 43 0 is wanted in the light of what has just been said the most obvious way is to set PRNDTL TEM1 1 0E 05 43 0 If the Satellite and solver are now run KOND will indeed be reported as 43 0 and the temperatures will have the appropriate values exactly as these of Step 11 Pay attention that Field Values of PRPS are missing as we have earlier set the index of the material used to zero Step 14 A still more successful way of setting the conductivity However since neither viscosity nor specific heat nor density have any relevance to the present problem and indeed the viscosity of solid steel must be considered as infinite the just used procedure which derives from the years when PHOENICS was concerned with fluids only may be regarded as rather circuitous There exists another way the conductivity can be set directly thus PRNDTL TEM1 43 0 whereby the minus sign is simply a signal to PHOENICS to treat the number which follows it as the thermal conductivity and not as a Prandtl number at all Running the executable now will confirm that the results are the same as before 3 Introducing temperature dependent material properties All the above methods shown in section 2 concern constant conductivities now in section 3 a method will be described for setting those which vary It involves the use of the In Form Input via Formulae feature of PHOENICS Step 1 Preliminary actions to set temperature dependent conductivity First an example will be shown namely that in which the thermal conductivity increases by AA for each degree of temperature rise and that AA equals say 1 0 We can express this fact in a way which PHOENICS understands by writing REAL AA To declare the variable aa AA 1 0 To set its value CHAR CONDUCT To have a character variable with which to CONDUCT PRNDTL TEM1 show that PRNDTL tem1 is the PIL variable to be used FORMULA 43 0 1 0 AA TEM1 100 To express the desired formula PROPERTY CONDUCT IS ENUL FORMULA to use it via Prandtl No Because the temperature rise was not very large with the previous heat input let us increase it 1000 fold remembering to bring down the COVAL statement which uses it HEATINPT HEATINPT 1000 but don t forget the COVAL which uses it COVAL HEATER TEM1 FIXFLU HEATINPT fix the heat input to HEATINPT and the formula for RAT FORMULA TEM1 0 5 HEATINPT XG XULAST XG KOND Correct formula STORED var RAT is FORMULA Calculates the temperature ratio LSWEEP 5 because the conductiviy has to be re calculated after the latest approximation to the temperature has been calculated we need several iterations 5 may be enough ISG21 LSWEEP This ensures that all 5 sweeps are completed NPRINT 1 and this causes print out to occur after every sweep IXMON NX 2 while this will provide a line printer plot of the centre slab temperature versus sweep Step 2 Running the case Running the case precisely as specified proves to be disappointing the conductivity stays at 43 0 However the reason proves to be that we left PRNDTL TEM1 equal to 43 0 and this meant that the In Form settings were by passed Re setting its default value is needed thus PRNDTL TEM1 1 0 Then In Form is allowed to do its work but not at the first sweep where the result appear as before thus Flow field at ITHYD 1 IZ 1 ISWEEP 1 ISTEP 1 Field Values of RAT IY 1 1 005E 00 1 0 1 0 1 0 1 0 IX 1 21 41 61 81 Field Values of KOND IY 1 4 300E 01 4 300E 01 4 300E 01 4 300E 01 4 300E 01 IX 1 21 41 61 81 Field Values of TEM1 IY 1 5 814E 01 1 895E 01 2 802E 01 2 779E 01 1 826E 01 IX 1 21 41 61 81 The reason is that it is only AFTER the first temperatures have been calculated that In Form knows by how much to increase the conductivity There are therefore sweep to sweep changes but by the fifth sweep the print out has reached it final content namely Field Values of RAT IY 1 1 005E 00 1 080E 00 1 111E 00 1 110E 00 1 078E 00 IX 1 21 41 61 81 Field Values of KOND IY 1 4 325E 01 5 050E 01 5 371E 01 5 363E 01 5 024E 01 IX 1 21 41 61 81 Field Values of TEM1 IY 1 5 781E 01 1 743E 01 2 492E 01 2 473E 01 1 684E 01 IX 1 21 41 61 81 Comparison of the two outputs shows that The conductivity has indeed increased the highest increase being in the middle of the slab where the temperature is greatest The temperatures are lower than before because the increased conductivity makes it easier for the heat to escape to the walls Inspection of the values of RAT however shows that they differ from unity Does that mean that the calculations are incorrect No what it results from is the fact that the formula which we have used for calculating RAT no longer corresponds to the exact solution of the differential equation Step 3 Checking the accuracy of the PHOENICS solution The exact solution of the differential equation for the problem which PHOENICS has just solved is somewhat complex but if our desire is solely to check whether PHOENICS is able to solve varying conductivity problems correctly we can do so by making the heat input non uniform also Indeed the task of checking is made easiest by using a concentrated rather than a distributed heat source at the central plane of the slab For this we need an odd number of cells with NX 101 say not 100 for only then will the grid truly have a central point Were we to leave NX at 100 we should have to provide sources at IX 50 and IX 51 for symmetry then the centre of the slab would lie between them Therefore its temperature would not be calculated and so could not be printed for checking This can be effected by introducing into the Q1 file the following statements NX NX 1 to create an odd GRDPWR X NX XULAST 1 0 number of cells i e 101 PATCH HEATER CELL NX 2 1 NX 2 1 1 1 1 1 1 1 to supply heat only to the central 51st cell and at a rate COVAL HEATER TEM1 FIXFLU 10 2 43 xulast 2 which would make the temperature arbitrarily equal 10 degrees if the conductivity were 43 NXPRIN 1 to print the results for every cell on either side of the central cell IXPRF NX 2 1 from 49th IXPRL NX 2 3 up to 53d When you do this you will have the following results Field Values of RAT IY 1 3 454E 01 3 524E 01 3 597E 01 3 524E 01 3 454E 01 IX 49 50 51 52 53 Field Values of KOND IY 1 4 695E 01 4 703E 01 4 710E 01 4 703E 01 4 695E 01 IX 49 50 51 52 53 Field Values of TEM1 IY 1 9 183E 00 9 364E 00 9 545E 00 9 364E 00 9 183E 00 IX 49 50 51 52 53 and will see that the central temperature is not 10 0 degrees but 9 545 as is appropriate because the conductivity has risen on average by nearly 5 You may care to experiment with other values of AA and other choices for centre point temperature and make other checks to assure yourself that PHOENICS is correctly calculating temperatures which accord with the exact solution of the differential equation this is for the chosen linear variation of conductivity with temperature the quadratic equation of the form T AA T 2 2 constant x Step 4 Understanding COVAL FIXFLU and FIXVAL Before proceeding further it is necessary to learn more about how sources of heat or for that matter of mass momentum or other quantity are represented in PHOENICS COVAL is a command with four arguments as seen above thus COVAL HEATER TEM1 FIXFLU 10 2 43 xulast 2 of which the third FIXFLU is used as a signal meaning insert a fixed heat flux with the following magnitude and the fourth is the magnitude itself However other arguments can be used For example to fix the value of temperature at 10 degrees precisely insert at the bottom of the Q1 file the line COVAL HEATER TEM1 FIXVAL 10 then make the run You will find that the central point IX 51 temperature is indeed 1 000E 01 It is natural to suppose that FIXVAL is another signal to the solver signifying insert a fixed value of temperature with the following magnitude This is indeed so but a more meaningful interpretation is insert a heat source of such a magnitude as will fix the temperature to the following value In order to find out more about FIXFLU and FIXVAL and incidentally to discover some of the idiosyncrasies of the PHOENICS Satellite paste the following lines at the bottom of your Q1 file NX To show how SATELLITE reports values FIXFLU To cause the value of FIXFLU to be displayed FIXVAL To do the same for FIXVAL But neither will work So now to trick SATELLITE into revealing their values REAL HOWBIG To declare a real variable mesg The next number is FIXFLU 10 HOWBIG FIXFLU 10 To set it equal to FIXFLU 10 HOWBIG NOW to find out FIXFLU s value HOWBIG FIXVAL 10 To do the same for FIXVAL mesg The next number is is FIXVAL 10 HOWBIG and the run the case Some messages will appear briefly on your screen and then disappear probably too rapidly for you to read them Never mind Such messages are always written also to the file satlog txt which you can open by clicking on the satlog txt icon indicated below You will then find them to be as follows NX 101 FIXFLU FIXFLU FIXVAL FIXVAL The next number is FIXFLU 10 HOWBIG 2 000000E 11 The next number is FIXVAL 10 HOWBIG 2 000000E 09 EARDAT file written for RUN 1 Library Case The explanation is this The value of any PIL variable can be displayed on the screen and in satlog txt by simply typing its name as is shown by the top line in respect of NX This might be expected to work for FIXFLU and FIXVAL also but it does not because PHOENICS believes that users will prefer to see in their RESULT files something to remind them of their intentions namely COVAL HEATER TEM1 FIXVAL 1 000000E 01 rather than the next line COVAL HEATER TEM1 2 000000E 10 1 000000E 01 which does not This is why we saw the unhelpful messages FIXFLU FIXFLU FIXVAL FIXVAL and were able to overcome this by introducing the factor of 1 10 We have thus learned that FIXFLU and FIXVAL are real numbers having the values 2 E 10 and 2 e 10 respectively All this might have been learned more easily by looking them up in the PHOENICS Encyclopaedia You may find it interesting to do this now by clicking on the hyperlinks FIXFLU and FIXVAL Also highly relevant is the Encyclopaedia article on COVAL indeed you are advised to read the first page of this so as to observe that there exists a comprehensive source of information about this PIL command of which only a summary can be given in the present tutorial The essential facts which you need to know now about COVAL and its four arguments are that the first argument is the name of the PATCH to which the source is to be applied the second is the name of the solved for variable named now as VAR in the present case temperature TEM1 the third and the fourth arguments named now as A3 and A4 are constants which appear in the equation which the PHOENICS solver uses to determine what source to apply namely source A3 A4 VAR in this special case in which A3 2 e 10 i e when it equals FIXVAL that constant is so large that the source becomes enormous whenever the difference A4 VAR is other than zero Therefore when VAR falls below A4 the source causes it to increase and when it rises above A4 the source causes it to decrease As a result VAR has to equal A4 exactly which we have indeed observed the temperature at the centre point did equal the specified 10 0 degrees In the other special case in which A3 2 e 10 i e when it equals FIXFLU the PHOENICS solver employs not the above equation but source A3 A4 A3 VAR i e source A4 A3 VAR which reduces since A3 is so small to source A4 which is precisely what is desired In order to consolidate your understanding now make runs in which you replace the constant FIXVAL by a smaller number e g 1 e5 thus COVAL HEATER TEM1 1 e5 10 You will find when you run the solver that the centre point temperature is less than 10 0 namely 9 823 Clearly

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  • How to Write geometry Files
    data file contains the following entries 8 the number of points 0 0000E 00 1 0000E 00 0 0000E 00 1 0000E 00 1 0000E 00 0 0000E 00 1 0000E 00 1 0000E 00 1 0000E 00 0 0000E 00 1 0000E 00 1 0000E 00 normalized coordinates 1 0000E 00 0 0000E 00 0 0000E 00 of the points 0 0000E 00 0 0000E 00 0 0000E 00 1 0000E 00 0 0000E 00 1 0000E 00 0 0000E 00 0 0000E 00 1 0000E 00 6 the number of facets 2 1 4 3 2 5 2 3 7 11 6 5 7 8 4 the point numbers building 1 6 8 4 14 the facets and colour number 8 7 3 4 13 1 2 5 6 15 3 1 3 5 the number of orientations and rotation codes Examination of the data file suggests that the file can be divided into three parts 1 a list of normalised coordinates for each point 2 a connectivity list for each facet showing how the facet is generated from 4 points 3 a rotation code which lists available orientations Part 1 The coordinate list The first line contains an integer in I6 format which gives the total number of points 8 in this case The next lines contain 3 real numbers in E12 5 format which are the normalized coordinates Note the following rules for entering data The character for the number of points on the top line should not be written beyond the 6th column for example a number 8 can be written in the 6th column but a number 18 should begin with the 5th column and a number 120 should begin with the 4th column and so on The order for entering the coordinates of the points is of no importance however once the coordinates have been entered numbers are allocated to the points on the first line is the point number 1 on the second the point number 2 and so on The X coordinates should not be beyond the 12th column the Y coordinates should not be beyond the 24th column and similarly Z coordinates should not be beyond the 36th column therefore the character length of each coordinates must not exceed eleven Part 2 The second part of the data file contains the connectivity information for each facet The number of facets 6 in this case is given before a set of lines indicating the point numbers which create these facets As mentioned above a facet is always defined by four points if a facet is formed from three points then a repeated point number must be entered twice The numbers are written as integers in I6 format The number of the point is the sequence number designated in the first part of the data file and has been described above A colour number is given at the end of each line The colour palette is given in Appendix A Again note

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  • seereslt.htm
    and address followed by date of expiry of licence Preliminary information about materials and properties Sometimes i e when READQ1 is set TRUE by the Satellite print out of text placed by the user in a special part of the Q1 Click here to find this Often information about constants used for particular model e g of turbulence A group by group statement of non default data settings similar in lay out to Q1EAR files grid geometry information for cartesian and polar coordinate simulations Below INTEGRATION OF EQUATIONS BEGINS tables of numbers representing values of physical quantities of the flow field such as pressure or velocity or numerically significant quantities such as imbalances in equations at various locations in space and time Which variables appear and with what frequency are controlled by the user by way of settings made in the input data file Q1 and especially those in Group 23 Summaries for all the computational cells in the domain of the residuals i e remaining imbalances of the equations of each solved for variable Information about the nett sources and sinks of the relevant physical entities e g mass momentum energy chemical species for each of the regions where

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  • for all species in a cell simultaneously whereas PHOENICS EARTH requires the properties for a single species for all cells in a slab at each call The differences in the order of data access are resolved by making the calls to the CHEMKIN and TRANLIB routines when the first species is accessed the properties are then stored in dedicated F array segments created using GXMAKE calls which have NX NY K elements Note that K is the number of species specified in the CHEMKIN input file The primary data input to PHOENICS is as usual through the Q1 file and it is the Q1 file that controls the options in the CHEMKIN interface However if the CHEMKIN SATLIT programme CHEMST is run the SATELLITE will read the CKLINK file and make settings on the basis of its contents However in addition to the EARDAT file generated by the SATELLITE from the Q1 file the user must supply the following CHEMKIN file CKLINK the CHEMKIN link file generated by the user from the mechanism file xxxx CKM by running the CKINTERP program and if the Sandia Transport Library is used to supply the transport properties TPLINK the Transport Properties link file generated by the user from the CKLINK file by running the TRANFIT program The data flow may be visualised thus xxxx CKM CKINTERP CKLINK TRANFIT TPLINK V V V Q1 SATELLITE EARTH If variable CSG4 is set in the Q1 file then the non blank characters of CSG4 are used to construct a file name for the CKLINK and TPLINK files For example if the setting CSG4 ho11 is made the CKLINK data will be read from the file ho11ckln and the TPLINK data will be read from the file ho11mcln The PHOENICS EARTH code will attempt to read the CKLINK and TPLINK files from the users private directory however if one of the files is not found then an attempt will be made read the file from the directory PHOENICS d earth d spefor d chmkin After a successful read will report the files used in the RESULT file and in the screen output The user may change the directories searched by modifying the appropriate lines of the EARCON file The same procedure is followed by the SATELLITE when the CHEMST coding is activated see below for further details 1 2 Basics of the Model a Specification of Composition There is a choice to be made regarding the variables used to specify the composition of the gas mixtures that will be used Compositions may be specified in terms of mass fractions Y mole fractions X and concentrations C From the point of view of the conservation equations to be solved the most convenient variables to use are the mass fractions Y For laminar cases the last species of the set is not solved but instead is derived from the mass fractions of the other species and the knowledge that the sum of all mass fractions must be 1 The

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