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  • ENC_S.HTM
    is a PIL command which prints on the screen the contents of the PHOENICS input file library SEELIB n or in the case of an option library SEELIB On where O is the letter appropriate to the option brings case n to the screen SEEPTS Command interactive SEEPTS command which permits the user to display at the VDU the values of the cartesian coordinates XC YC ZC of all the points of a BFC grid within the sub domain defined by the six arguments of SEEPTS viz SEEPTS I first I last J first J last K first K last This command is used primarily in conjunction with SETPT and VIEW as an aid to making localized improvements to the grid For further details of this BFC nomenclature see BODY F also see GROUP 6 for a list of BFC commands Segment S Photon Help Segment is the name of the current GEOMETRY segment The default is SEGM level where level is the nesting level SELREF SELREF self selection of reference residuals RESREF the iteration cut off threshold for the residuals of a solved for variable is selected internally in PHOENICS when the PIL variable SELREF the default is set T See also the entry for RESFAC SENDP Autoplot Help SE NDP Sends the current picture to a plotting device if one is available See also HELP on DUMP SAVE SENDP Photon Help SE NDP Redraws the current picture on a plotter or into a plot file If more than one plot device is configured in the Graphics Interface a plot device can be selected from a menu of the available devices If a file name is required PHOTON will prompt for it See also DUMP SAVE SENDP Photon Help SE NDP Redraws the current REPLAY display on a plotter or into a plot file If more than one plot device is configured in the Graphics Interface a plot device can be selected from a menu of the available devices If a file name is required REPLAY will prompt for it Sequential file A type of data file used by PHOENICS in which the information is accessed sequentially rather than directly cf direct access file Sequential formatted files are slower to access than direct access files but they have the advantage of being portable across machines of different makes SETBFC is a PIL variable which when set true activates a call to the open source sub routine GXBFGR in file GXBFGR HTM where Fortran coding may be found or placed by the user which calculates the values of XC YC and ZC the cartesian coordinates of the grid cell corners Shade Colr Photon Help Shade Colr activates a colour bar showing all the available colours You can choose a preferable colour by pointing the cursor at the particular colour and clicking the mouse button There are three colours RED GREEN BLUE for shading The subsequent plot with Do will be coloured accordingly Shear stress equation in RSTM see TR305 SHIFT SHIFT X SHIFT Y Autoplot Help SH IFT X or Y a i j A constant increment a is added to the x or y coordinates of data elements i j If these are omitted the program will prompt See also HELP on DIVIDE X DIVIDE Y MULTIPLY X MULTIPLY Y SHIFT Replay Menu Photon Help SH ift is a REPLAY command which sets the position of the next frame It is used with SCALE in order to draw frames with specified positions and sizes on the display Issuing the SHIFT command causes the graphics cursor to be displayed when the position has been selected an alphanumeric key should be pressed to fix the position This position is used as the bottom left hand corner of subsequent frames until reset via a SHIFT or RESET command This command can be used in USE files where interaction with the user is not possible However the format of a SHIFT command in a USE file is USHIFT X position Y position where the X and Y coordinates are given in PHOTON units The WHERE command can be used to return screen positions in a form suitable to be used by SHIFT when SHIFT is employed in a USE file See also DUMP REPLAY SCALE WHERE RESET REDRAW DRAW SHSOA Real group 13 SHSOA is used in a version of the two fluid turbulence model to specify the strength of the shear source See the help and encyclopaedia entries on TURBUL and TURMOD and GXSHSO for further information SIMPLE SIMPLEST These are methods also called algorithms used in PHOENICS for the solution of the systems of algebraic equations for velocity components and pressure SIMPLE stands for Semi Implicit Method for Pressure Linked Equations It was first published by Patankar and Spalding 1973 The method used in PHOENICS is SIMPLEST SIMPLE ShorTened which is a derivative of SIMPLE These algorithms are described here Size Test Menu Photon Help Size changes the size of the characters in an existing text string PHOTON will show all four character sizes near the bottom of the window Select the desired size with the cursor PHOTON will then request the text string to be resized See also SIZE in the menu below Size Contour Menu Photon Help Cells are filled with polygons of a specified size Size Stream Set Menu Photon Help The time step size for each step of streamline tracking The smaller the time step size the more accurate the streamlines will be Size Number Depth Int Contour Menu Size Number Photon Help The number shown here depends on the contour mode Fill can be Size Number or Depth depending on which has been chosen in the Set menu Isoline is the number of contour intervals You can change the settings as required See also Set SKIP Character flag groups 11 13 and 23 SKIP is recognized in the SATELLITE and EARTH as a special PATCH name which causes the PATCH in question to be skipped i e it is a means of deactivating a PATCH For example the instructions PATCH AREA1 EAST 1 1 1 1 1 1 1 1 AREA1 SKIP would cause the PATCH arguments to be stored but would inhibit the otherwise implied actions In order to reactivate the PATCH rename the PATCH name back viz SKIP AREA1 alternatively in Q1 simply remove the statement which sets AREA1 to SKIP by means of the system editor When it is desired to deactivate several PATCHes which may later need to be revived proceed by renaming each PATCH name to SKIP1 SKIP2 SKIPn so as to retain their separate identities eg PATCH ONECELL EAST 1 1 1 1 1 1 1 1 PATCH IXEQNX WEST NX NX 1 1 1 1 1 1 PATCH SOURCE PHASEM 1 NX 1 NY 1 NZ 1 LSTEP ONECELL SKIP1 IXEQNX SKIP2 SOURCE SKIP3 If it is desired to re activate PATCH IXEQNX this is achieved by re naming the PATCH named SKIP2 to IXEQNX by the instruction SKIP2 IXEQNX Slab wise variables SWVs SWVs are variables which although they may have significance for all the cells in a 3D grid are stored only in arrays of dimension NX NY As the equation solving operation moves through the grid in the z direction the values pertaining to the previously visited slab are over written by the values pertaining to the currently accessed slab The majority of variables with integer names used inside PHOENICS are of this kind Examples are all those beginning with LXY in COMMON LB of GRDLOC The special auxiliary variables described above may as already mentioned be either FFVs or SWV s They are the latter by default ie if no specific action is taken in the SATELLITE in order to create full field storage for them Of course when the grid does not extend in the z direction ie when NZ equals 1 full field variables are also in a certain sense SWVs The variables in the X wise Y wise and Z wise categories have only one distinct value for each and every value of the coordinate in question The lengths of the F array segments which they occupy are therefore NX NY and NZ respectively Examples are XWV s the distance or angle x from the origin to a cell centre and the difference in x value between successive u velocity locations YWV s the radial distance from the symmetry axis to a cell centre and the difference in y value between successive v velocity locations ZWV s the distance z from the origin to a w velocity location and the difference in z value between successive cell centres Because of the slab by slab nature of the PHOENICS storage and equation solving arrangements there are more ZWV s than there are XWV s and YWV s The variables in question are those which appear in the COMMON block LB of GRDLOC in Appendix 2 as LX for x wise variables LY for y wise variables LZ for z wise variables Slabs Slabs are arrays of cells having the same value of the low to high coordinate z Many of the mathematical operations conducted by PHOENICS operate over a single slab and many cycles of adjustments can be performed for one slab before PHOENICS transfers its attention to the next slab These adjustment cycles are referred to as slabwise solutions Slabs hydrodynamic iterations of see LITHYD Slabs number of iterations during a sweep of see LITC Slabwise iterations see LITHYD SLBSOL Ground logical SLBSOL is set TRUE by EARTH when the NX NY linear equations of the current variable INDVAR at the current slab are to be solved It is set FALSE by EARTH when the NX NY NZ linear equations of the current variable INDVAR are to be solved over the whole field See USOLVE SLIP VELOCITY STORAGE FOR TWO PHASE FLOW Storing the variable SLPU SLPV and or SLPW ensures that the differences between first and second phase velocities are computed and stored at the end of iterations on a slab They can be used for the plotting of slip velocity vectors in PHOTON The relevant sequence in GREX3 is SLIPVL NOT ONEPHS AND LBNAME SLPU NE 0 OR 1 LBNAME SLPV NE 0 OR LBNAME SLPW NE 0 Library case W582 provides an example Slope angle of see SNALFA SLPU See PHENC Slip velocity storage SLPV See PHENC Slip velocity storage SLVR This character variable which is an abbreviation of the word SOLVER is used in GROUND coding to indicate which solver is to be used Current options are FGEM for PARSOL and or fine grid embedding GAUS for the Gauss Seidel solver CGGR for the conjugate gradient solver CRGR for the conjugate residual solver It is not used for MIGAL which is activated in a different manner SLVR is equivalenced in the included file GRDLOC to CSG3 which is the variable which must be used in the Q1 file SLPW See PHENC Slip velocity storage Smagorinsky subgrid scale model See PHOENICS encyclopaedia entry Smagorinsky subgrid scale model SMCHCK Real default 1 E30 group 25 SMCHCK lower limit for F array element INCHCK SNALFA Real default 0 0 group 4 SNALFA sine of the angle of slope of the y 0 0 boundary for use in parabolic calculations when a cylindrical polar coordinate system is in use ie PARAB T CARTES F When SNALFA is non zero the z direction is measured along the surface of the body the y direction is measured normal to it and x in radians is circumferential SOLID STRESS and STRAIN See PHENC entry Solution procedure for RSTM see TR305 Solution sweeps specifying number of see LSWEEP SOLUTN Command group 7 SOLUTN command for stating which variables are to be stored solved etc The format of the command is SOLUTN variable index Y or N Y or N six times if uncertain enter P for pass The six questions answered by the Y s and N s are Store the variable Solve for the variable Solve by whole field method Solve by point by point method Use explicit formulation if transient Use harmonic averaging of exchange coefficients The defaults are N N N N N N The explicit question is relevant only to time dependent flows The harmonic averaging question relates to how the diffusion coefficients or viscosities are averaged in order to provide the values used in the finite domain equations When N is answered arithmetic averaging is used See STORE for a way of storing and printing out the residuals and corrections of the solved for variables SOLVE Command group 7 SOLVE command for stating which variables are solved thus SOLVE variable name 1 variable name 2 The above command causes the following lower level commands to be executed SOLUTN variable name 1 Y Y N N N N OUTPUT variable name 1 Y N N N Y Y SOLUTN variable name 2 Y Y N N N N OUTPUT variable name 2 Y N N N Y Y etc If the variable name is not one of the recognized ones See VARIABLES to list these the code will search from NPHI downwards until it finds an unused variable ie one not stored this will then be solved and named as requested See STORE for a way of storing and printing out the residuals and corrections of the solved for variables SOLVED Command This command prints on screen all currently solved variables Solver Solver parameters for the Stone type linear equation solver The speed of convergence of the default linear equation solver of PHOENICS can be influenced by settings of the following PIL variables each of which has its own Encyclopaedia entry LITER variable index ENDIT variable index ISOLX ISOLY and ISOLZ and OVRRLX IVARBK and ISOLBK SORT Advanced PIL command The syntax is SORT ARRAY FUNC IMAX This command sorts the array ARRAY according to the function specified in FUNC The allowed functions are ASC sort into ascending order DSC sort into descending order ASCR sort into ascending order remove duplicate entries DSCR sort into descending order remove duplicate entries ASCRT sort into ascending order remove duplicate entries using a tolerance DSCRT sort into descending order remove duplicate entries using a tolerance IMAX specifies the extent of the sorting For 2 3D arrays there are additional arguments as for LOCATE which indicate which particular row column or plane is to be sorted All other elements are then sorted to match the specified one If removal of duplicates is specified then IMAX returns the number of elements left after sorting If a tolerance is used it is set as an additional last argument The element is removed if the absolute difference betrween two adjacent elements is less than or equal to the set tolreance The tolerance can be any valid PIL real variable ARRAY can be any valid PIL real or integer array and IMAX can be any valid PIL integer SOURCE See also nett sources SOURCEs can be set in the following two ways Built in sources are activated by putting Y as the second argument of the command TERMS for the variable in question This is the default value except for TEM1 and TEM2 The built in sources are the pressure gradient source for U1 U2 V1 V2 W1 and W2 the centrifugal and Coriolis sources for U1 U2 V1 and V2 in cylindrical polar coordinates CARTES F the negative of the substantial derivative of pressure for H1 and H2 and the dissipation of mechanical energy into heat for H1 and H2 All other sources have to be introduced by the user who defines through PATCH the section of the domain over which they act and through COVAL the nature of the source Often of course GROUND called functions will require to be activated by the setting of the Coefficient or the VALue of COVAL to GRND GRND1 etc but many settings are capable of being made more directly For example the type PHASEM provides a convenient way of introducing GRAVitational sources in cartesian coordinates Subroutine GREX is supplied with a set of often needed source term options These options are accessed by PATCHes that have names that begin with the characters BFC BUOY CHSO CONM IBFC IPST KESO LATG LESO NE OUTL PROF RADI ROTA SHSO UPOL VPOL Sources in finite volume equations See USOURC logical Group 8 Sources representing inflow boundaries see ONLYMS real flag Group 13 Sources setting of per unit free area or volume see FREEE FREEH FREEN FREEVL flags Group 13 Sources setting of per unit east see EAST real flag Group 13 Sources setting of per unit high see HIGH real flag Group 13 Sources setting of per unit low see LOW real flag Group 13 Sources setting of per unit north see NORTH NWALL flags Group 13 Sources setting of per unit south see SOUTH and SWALL real flags Group 13 Sources setting of per unit volume see VOLUME real flag Group 13 Sources setting of per unit west see WEST and WWALL real flags Group 13 SOUTH Real flag value 5 0 group 13 SOUTH is a PATCH type used for setting sources per unit south ie smaller y area by way of COVAL in group 13 Spatial subdivisions in x direction specifying number of see NX Spatial subdivisions in Y direction specifying number of see NY Spatial subdivisions in Z direction specifying number of see NZ Spin View Menu Photon Help The image can be rotated in the view plane SPINTO i e Simplified PINTO This new 2009 successor to PINTO is a stand alone module the purpose and use of which are described here Its main use is to procure economies in computer time by performing a series of runs starting with coarse grids and proceed via re starts to the finest grid Spot values Spot values sometimes called monitor point values or monitor values are the values of solved for

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  • ENC_T.HTM
    VR Reference Guide TR326 Three dimensional grids in PINTO see TR218 THRME1 Integer used in GXTHRMX to denote 1st phase volumetric thermal expansion coefficient THRME2 Integer used in GXTHRMX to denote 2nd phase volumetric thermal expansion coefficient TICK command in AUTOPLOT TI CK Cause axis tick marks to be drawn on other side of axes Revert to original by repeating TICK See also HELP on AXES BOX FRAME TIM TIM is a Fortran real variable used in GROUND It represents the current time TIMA PIL real group 13 TIMA is used to specify the wave amplitude of a periodic source term See the help and encyclopaedia entries on and GXTIM for further information Time arguments setting of see GRDPWR command Group 2 Time Out feature PHOENICS permits users to set the maximum clock time of a simulation calculation by setting the PIL variable MAXSEC to the maximum allowable number of seconds It was introduced for the convenience of users of CHAM s pay by use Remote Computing Service However it may of course be used in stand alone installations also The coding which effects this is in the open source file grex3 htm This employs the following call to an in EARTH sub routine CALL SECONDS NUMSEC which returns the number of seconds of time which have elapsed since the EARTH run started to execute In the GREX3 sequence provided by CHAM NUMSEC is simply compared with ISG20 in order to determine whether execution is to cease Users who incorporate it in their own coding may well find other uses for it Time as a plotting direction in PHOTON If NZ 1 and STEADY F it is possible to dump field values which can be plotted by PHOTON with the time dimension replacing Z In order to activate this feature it is necessary only to set IDISPA 0 in the Q1 file then because of the statement IF NOT STEADY AND IDISPA GT 0 AND PNAM EQ CALL GXPARA in Group 19 Section 8 of GREX3 F a call is made to subroutine GXPARA IDISPA dictates the frequency in terms of time steps of dumping The file containing the dumped information is called PARPHI if PHIDA F in PREFIX and otherwise PARADA The first time step at which dumping occurs is IDISPB and the last is IDISPC However if these are left as zero dumping occurs for the whole time range Time direction setting number of regions for see NREGT Group 2 Time step setting index number for see LSTEP Time marching computations see STEADY Time step interval print out of see NPRMNT Time step intervals setting of see TFRAC Time step specification see GROUP 2 TINY Real flag value 1 E 20 TINY a small real number defaulted to 1 E 20 which is used in EARTH to guard against division by zero This value may be too small for machines with short word length and would normally be set to an appropriate value at the time of installation When TINY LE 1 E 20 underflow trapping occurs at various locations in the calculation Setting TINY to a higher value therefore saves some time and is acceptable for most problems on most machines TITLE PIL character TITLE is a special character variable which contains the character string generated by the TEXT command Its default setting is NAME TITLE OF RUN HERE MAX OF 40 CHARS This variable should be treated as a read only PIL variable Only the TEXT command should be used to modify it TITLE Photon Help After pressing the button type in the title of the current frame to be saved in the PHOTON save file TLAST PIL real default 1 0 group 2 TLAST multiplier of TFRAC If TLAST is set to GRND EARTH visits group 2 of GROUND for a setting of the time step size DT rather than DT being determined from the settings of TFRAC See the Encyclopaedia for full details To Photon Help The last GEOMETRY element to be DELETE ed or turned ON OFF TOLERANCE Tolerance is a variable having the dimensions of distance which the VR Editor uses when creating a grid containing VR objects which are specified as affecting the grid All such objects do so by default Three tolerance values can be set one for each of the Cartesian coordinate directions By default all three are set to 0 001 m Affecting the grid means requiring the Satellite to create region boundaries co incident with the edges of the object s bounding box The grid can then be specified within each region either automatically or manually If the distance between two region boundaries or a region boundary and the domain edge is less than the tolerance in that direction the second region boundary will not be created If it is desired that an object should not create region boundaries the part of the Q1 file which pertains to it should contain OBJ GRID NO if the object is not to affect the grid in any direction or OBJ GRID p p p where p is Y for Yes or N for No for the X Y and Z co ordinate directions respectively Tolerance values can be specified by the user either interactively or by editing the RSET M line in the Q1 file Judicious settings for the tolerance can help eliminate very thin spaghetti cells formed when objects almost but not quite line up TRACE PIL logical default F When set equal to T TRACE switches on a primitive tracing facility in the Q1 file which functions as an aid to debugging complicated Q1 files After the command TRACE T has been read each line of PIL is written either to the VDU or to the file lupvr depending on the PHOENICS version with the message 123 45 TRACING prefixed to it before it is interpreted by the Satellite The numerical value prefixing the line shows the current machine clock time in seconds The line printing procedure

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_enc/enc_t.htm (2016-02-15)
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  • ENC_U.HTM
    to be found It is therefore unwise to use the poluda command on these files only boot should be used UDIFF Logical default F group 8 UDIFF must be set to T if diffusion fluxes are to be accessed or altered in group 8 of GROUND UDIFNE Logical default F group 8 UDIFNE may be set to T if diffusion neighbours are to be accessed or altered in group 8 of GROUND UDS Upwind differencing scheme see TR304 UGEOM Logical default F group 6 UGEOM when set to T permits current z slab geometry to be changed in group 6 of GROUND at the beginning of each iz slab visitation UNDER PRESCRIPTION of input data a common code user error A common mistake is to set problems for which there is no unique answer For example an incompressible fluid may be caused by some momentum source to circulate steadily within a fixed volume cavity then although the pressure DIFFERENCES which prevail within the cavity can be uniquely computed the ABSOLUTE LEVEL of pressure can not PHOENICS will find this situation confusing especially when the pressure level drifts to such large values that round off errors result when it subtracts the pressure at one point from the pressure at a neighbouring point as it is required to do when solving for velocity In such circumstances PHOENICS must be given more information Thus the pressure might be arbitrarily fixed to zero say at an anchor point within the flow domain by means of appropriate PATCH and COVAL commands Similar difficulties may arise with temperature for example when the flow is steady and all the surroundings are insulated Specification of the temperature at one point at least is essential Another mistake of the same kind is to seek to simulate in a steady flow manner a two phase phenomenon occurring within a container into which only one of the phases is continuously supplied and when there is no transfer of mass between the phases An example is the bubbling of a gas through a liquid held in an open topped tank Such problems have no unique solution for what can determine the amount of the non supplied phase which will be present in the container It is only by setting STEADY F and providing appropriate initial conditions that the flow which is to be simulated can be uniquely determined Alternatively the boundary conditions must be changed in some way which makes the steady flow formulation physically meaningful for example by the provision of non zero inflows for BOTH phases Under relaxation see RELAX LINRLX FALSDT DTFALS EXPERT and SARAH Under relaxation of pressure in non orthogonal grids The PIL setting RELAX P2 LINRLX factor where factor is a real number multiplies the continuity errors by factor before they enter the pressure correction sequence This may be a more effective solution smoothing sequence than under relaxing the pressure correction itself because it results in reduced for factor 1 0 velocity adjustments RELAX P2 has no influence on the P2 values themselves Underline Text menu Photon Help Underline shows whether the current TEXT element is underlined It can be changed here UNEQUAL Autoplot Help UNE QUAL Opposite of EQUAL Forces return to normal axis scaling See also HELP on EQUAL UNIT CONVERSION FACTORS 1 ft 0 3048 m 1 lb 0 4539 kg 1 Btu 0 2520 kcal 1 055 056 J 1 kcal 4 186 8 J 1 bar 100 000 N m2 Units Vector Edit Menu Photon Help Units set the current units of the vector It is shown at the bottom of the colour bar and by the reference vector if the Key option is Yes Units Contour Edit Menu Photon Help Units set the current units of the variable to be contoured It is shown at the bottom of the colour bar Unlocking string String of characters and numbers provided by CHAM which once inserted in the file CONFIG unlocks the use of PHOENICS The unlocking string contains encoded information about the NODE ID the licence duration modules and features licensed UP Photon Help U p direction changes the orientation of the plot The up direction is any vector is 3D space which appears vertical when projected onto the screen See the help entry for VIEW for details on how to specify directions For example UP Y sets the Y axis as the up direction NOTE that the UP and VIEW directions cannot coincide by definition See also VIEW UPAUSE in Satellite When placed in a Q1 file this PIL command will cause the processing of the file by the Satellite to be paused The message Press RETURN to continue will then appaear in the screen and remain until RETURN is indeed pressed UP X Photon Help Sets the UP vector to 1 0 0 UP Y Photon Help Sets the UP vector to 0 1 0 UP Z Photon Help Sets the UP vector to 0 0 1 UPAUSE Photon Help UPA use nsecs is used within USE files to perform a timed pause It differs from PAUSE in that no user input is required instead a timed pause of length proportional to the nsecs parameter is performed The value of nsecs needed to produce a given time interval will be machine dependent See also PAUSE UREWIND Upper limit Contour edit menu Photon Help The maximum value of the current contour range if the RANGE option is on Upward stream set menu Photon Help Streamlines will be tracked upstream from the starting positions Upwind differencing In the upwind differencing scheme the diffusive flux is present irrespective of the cell Peclet number whereas in the hybrid scheme the diffusive flux is cut out for Peclet numbers in excess of 1 0 DIFCUT See the Encyclopaedia entry DIFCUT for further information UREWIND Photon Help URE wind is used within USE files to rewind the file and restart processing from the start of the file It should be used with extreme care as

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  • ENC_V.HTM
    persons than any other and over a longer period the claim can also reasonably be made that it is the BEST validated CFD code VALUE Command group 13 This command is used to declare non zero values of mass flow velocity pressure and scalar variables associated with INLETs OUTLETs and WALLs The syntax is VALUE NAME PHI VALUE NAME is the name of the boundary condition as used in the associated INLET OUTLET or WALL command PHI is the affected variable and VALUE is the required value Mass flow and pressure are both set by reference to the variable P1 For mass flows INLET the value should be the mass flow unit area whereas for pressure OUTLET it should be the required external pressure The function of the command is to set the 4th argument of the COVAL for the variable PHI in the patch NAME to VALUE The coefficient is left at its previous setting or is set to 0 0 if no COVAL existed before See the entries on SOURCE PATCH and COVAL for further details Value Surface menu Photon Help Value specifies the value of the variable on the surface VAN Driest damping model See PHENC entry The VAN Driest low Reynolds number mixing length model VC1 PIL integer flag VC1 name used to denote the first phase co located velocity component in the y direction VCRT PIL character flag group 7 VCRT integer name recognized by EARTH denoting first phase cartesian YC directed velocity resolute See UCRT VELAD VELAD is an integer index usable in subroutines called from GROUND for accessing the 2D array of values pertaining to the current IZ slab of additions to the current slab velocities at the point in the computation at which the convection fluxes are assembled VELOCITY RESOLUTES AT INLETS boundary conditions for see BOUNDARY CONDITIONS FOR VELOCITY RESOLUTES AT INLETS Velocity variables The velocity variables for which PHOENICS solves are always the resolutes of the velocity vector in the direction of the line joining the grid points on either side of the cell faces at which velocities are stored For cartesian grids these variables are therefore the cartesian velocity resolutes For cylindrical polar grids they are the axial radial and circumferential resolutes For general curvilinear grids they are the resolutes of the velocity vector in the local direction of the lines connecting the nodal points PE PN and PH In vector terminology U V and W are equal to the scalar products of the velocity vector with the unit vector aligned with the direction PE PN and PH respectively Velocity adding extra see U1AD U2AD V1AD V2AD W1AD W2AD Group 8 Velocity print out of see IURPRN integer Group 21 VISCLM Integer used in GXKNVSL to denote laminar kinematic viscosity VISTRB Integer used in GXKNVST to denote turbulent kinematic viscosity VLSQ When STORE VLSQ appears in the Q1 file and velocities are being computed PHOENICS will compute and print the 3D stored variable VLSQ which represents the value of

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_enc/enc_v.htm (2016-02-15)
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  • ENC_W.HTM
    which the rapid temperature dependent reaction rates accentuate the local non uniformities The macro WSR is therefore by far the more realistic object of study The names of the models will be abbreviated to IWSR the I coming from Ideal or mIcro and AWSR the A coming from mAcro or Average from now on The following description exemplifies the AWSR idea It is taken from MFM library case L001 htm Stirred reactor with a 1D population distribution and reactedness ranging from zero to 1 as the population distinguishing attribute It is supposed that two streams of fluid enter a reactor which is sufficiently A well stirred for space wise differences stirring of conditions to be negligible but not C sufficiently for micro mixing to be paddle complete B The two entering streams have the same elemental composition but one may be more reacted than the other 2 Extinction of combustion in an IWSR The different behaviour of the two kinds of WSR is well highlighted by consideration of that dramatic and practically important phenomenon of combustion systems known as extinction by which is meant the transition from a finite rate of burning to a near zero rate which results from a small change in the operating conditions The analysis for IWSRs is the simpler and will be presented first for the case of a single entering stream of pre mixed fuel and oxidant The following diagram from an old lecture forms the starting point It shows the typical shape of the dependence of the rate of reaction on the reactedness i e the extent to which reaction has progressed As indicated by the abscissa legend reactedness can be measured for an adiabatic system by the dimensionless temperature rise where Tu stands for the temperature of the fully unburned gas and Tb for that of the fully burned gas combustion 11 2 The simple chemically reacting system lecture SCRS 5 1 20 Reaction rate for fixed f and h oxygen x x x x x reaction unburned fuel x rate R x x x x 0 reactedness r T Tu Tb Tu 1 The shape of the reaction rate curve is easily understood if it is recalled that the rate increases rapidly with temperature which explains the concave upward shape of the left hand part of the curve it must fall to zero when the concentration of either of the reactants fuel or oxidant becomes zero and this happens as is shown by the two straight lines on the diagram when the burned gas temperature is reached Now let it be recalled that in the steady state two relations between r and R must be obeyed namely that indicated above and another which expresses the conservation of fuel mass namely Mdot mfu u r R vol where Mdot mass flow rate of the entering fuel bearing stream mfu u mass fraction of fuel in this stream and vol reactor volume This relation can be expressed as a straight line through the

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  • ENC_X.HTM
    used for the balances of all variables except for NX greater than 1 x direction velocity components U1 and U2 Distances or angles if CARTES F so that x is measured in radians are measured from the low x i e extreme west boundary of the flow domain XFRAC values may be set by means of any of the methods described for TFRAC XG2D XG2D is an integer index usable in subroutines called from GROUND for accessing the 2D array of values pertaining to the current IZ slab of either for CARTES T or BFC T distances of the centres of the continuity cells from the x 0 0 plane in a Cartesian coordinate system or for CARTES F and BFC F angular coordinates of the centres of the continuity cells in a cylindrical polar system Note that this index is present only if CALL MAKE XG2D is present in Group 1 Section 1 of GROUND XL Photon Help XL specifies the last I index of the current plotting region The default value is NX 1 for GRID and NX for other plotting elements XRAT XRAT is a Fortran real variable used in GROUND It represents the multiplier of the previous XULAST which gives the current XULAST XU2D XU2D is an integer index usable in subroutines called from GROUND which has a significance similar to XG2D except that the east faces of continuity cells are involved not cell centres Unlike XG2D XU2D has no significance when BFC T Note that this index is present only if CALL MAKE XU2D is present in Group 1 Section 1 of GROUND XULAST Real default 1 0 group 3 XULAST is the overall length of the integration domain in the x direction measured in metres for CARTES T and in radians for CARTES F The U in the name is a reminder that the staggered grid arrangements entail that the extremity of the domain in the x direction is occupied by a velocity specifically U1 and U2 location Grid points at which pressure temperature volume fraction and other scalar quantities are located lie halfway between velocity locations In parabolic calculations XULAST can be changed as a function of downstream location by means of the parameter AZXU XYZ Photon Help XYZ is used to specify the name of a PHOENICS BFC grid file XYZ or XYZDA file which PHOTON will attach in order to allow viewing of BFC grids Before attaching the grid PHOTON enables the specification grid scaling factors When a grid file has been attached for viewing by means of the XYZ command all commands which rely upon data from a PHI file eg VECTOR CONTOUR SURFACE are invalid and the PHI command must be used to attach a PHI file before these commands can be used See also PHI file XYZ command in PHOTON It is possible to view body fitted co ordinate grids alone within PHOTON without you having to attach a fields file The XYZ command prompts you to enter

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_enc/enc_x.htm (2016-02-15)
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  • ENC_Y.HTM
    F YC is also a GROUND accessible real function returning the corner coordinate value See also SUBROU YCEN When the Q1 file contains BFC T and STORE YCEN the values of the cell centre y coordinates are printed in the result file They may also be accessed and used by In Form statements YF Photon Help YF specifies the starting J index of the current plotting region The default value is 1 YFRAC PIL real array default 100 1 0 gro YFRAC Array for use in setting the y direction coordinates of the north faces of the computational cells used for the balances of all variables except for NY greater than 1 y direction velocity components V1 and V2 Distances are measured from the low y i e extreme south boundary of the flow domain YFRAC values may be set indirectly by means of the commands GRDPWR SUBGRD or by one of the two methods described for TFRAC In polar coordinates CARTES F and BFC F the YFRACs measure distance from the inner boundary of the domain which is separated from the axis of symmetry by the radial distance RINNER YG2D Integer index used in GROUND YG2D EARTH index used to access the 2D array of values pertaining to the current slab of the distances of the centres of the continuity cells from the y 0 0 plane for CARTES T or BFC T or cylinder for CARTES F and BFC F See RINNER Note that this index is present only if CALL MAKE YG2D is present in Group 1 Section 1 of GROUND YL Photon Help YL specifies the last J index of the current plotting region The default value is NY 1 for GRID and NY for other plotting elements YPLS PIL logical group 25 YPLS is used

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_enc/enc_y.htm (2016-02-15)
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  • ENC_Z.HTM
    the Cartesian coordinate z of the corners of the continuity cells See also XC YC and BODY F ZC is also a GROUND accessible real function returning the corner coordinate value See also SUBROU ZCEN When the Q1 file contains BFC T and STORE ZCEN the values of the cell centre z coordinates are printed in the result file They may also be accessed and used by In Form statements ZDIFAC PIL real default 1 0 group 8 ZDIFAC proportion of z direction diffusion coefficient added to the denominator of the finite volume correction equation when the whole field solver is not used Positive values less than 1 0 may accelerate convergence when z direction diffusion is strong Since this acts only on a coefficient of the correction equation it does not affect the final solution but only the speed with which the solution is reached ZF Photon Help ZF specifies the starting K index of the current plotting region The default value is 1 ZFRAC PIL real array default 100 1 0 ZFRAC Array for use in setting the z direction coordinates of the high faces of the computational cells used for the balances of all variables except for NZ greater than 1 z direction velocity components W1 and W2 Distances are measured from the low z i e extreme low boundary of the flow domain ZFRAC values may be set indirectly by means of the commands GRDPWR SUBGRD or by one of the two other methods described for TFRAC ZGNZ ZGNZ is an integer index usable in subroutines called from GROUND for accessing the 2D array of values pertaining to the current IZ slab of the distances of the centres of the continuity cells from the z 0 0 plane The array is accessed via GETZ and holds values for all IZ ZL Photon Help ZL specifies the last K index of the current plotting region The default value is NZ 1 for GRID and NZ for other plotting elements ZMOVE PIL real flag value 10230 0 ZMOVE Set W1AD ZMOVE in order to inform EARTH that the z wise moving grid option is to be used This moving grid option permits the z wise grid to be sub divided into any number of parts up to NZ which may be specified as stationary moving and expanding or contracting by way of subroutine GXPIST in section 1 of group 19 of GROUND Subroutine GXPIST called from GREX supplies an example of a 2 part grid suited to piston in cylinder calculations The control parameters for this option are IZW1 AZW1 BZW1 and CZW1 GXPIST presumes that the settings of the grid distribution by ZFRAC are for the grid when the piston is at bottom dead centre The following diagram depicts a 3 part grid suited to piston in cylinder calculations when the cylinder head has a cavity in it which requires a fixed grid 1 z 1 1 IZW 1 IZW 2 IZW 3 1 1 1 2

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_enc/enc_z.htm (2016-02-15)
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