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  • Grid Generation Using PIL Commands
    grid generation Grid Generation Using PIL Commands CONTENTS Part 1 BFC grid generation tutorial Part 2 Cartesian polar grid and time setting tutorial Part 3 BFC grid generation examples Part

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_tuts/grid/grtut0.htm (2016-02-15)
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    same way as GRND see GRND for details but permits GROUND to distinguish options according to value For example subroutine GXRHO distinguishes the following options amongst others RHO1 GRND1 for an enthalpy dependent density field and RHO1 GRND3 for an isentropic gas law density field See PHENC entry GRNDx GRND2 Real flag value 10130 0 groups 2 3 4 5 9 10 11 and 13 See PHENC entry GRNDx GRND3 Real flag value 10140 0 groups 2 3 4 5 9 10 11 and 13 See PHENC entry GRNDx GRND4 Real flag value 10150 0 groups 2 3 4 5 9 10 11 and 13 See PHENC entry GRNDx GRND5 Real flag value 10160 0 groups 2 3 4 5 9 10 11 and 13 GRND6 Real flag value 10170 0 groups 2 3 4 5 9 10 11 and 13 See PHENC entry GRNDx GRND7 Real flag value 10180 0 groups 2 3 4 5 9 10 11 and 13 See PHENC entry GRNDx GRND8 Real flag value 10190 0 groups 2 3 4 5 9 10 11 and 13 See PHENC entry GRNDx GRND9 Real flag value 10200 0 groups 2 3 4 5 9 10 11 and 13 See PHENC entry GRNDx GRND10 Real flag value 10210 0 groups 2 3 4 5 9 10 11 and 13 See PHENC entry GRNDx GRNDx ie GRND1 GRND2 GRND10 and their equivalents Since the earliest days of PHOENICS these variables have been used for making selections in the Q1 file of options in GROUND files Starting with version 2 2 SATELLITE recognises certain equivalents the names of which indicate the meanings of the choices The following lists enumerate these The equivalent names may be entered with either upper or lower case characters More such equivalents will be introduced for

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_enc/grnd.htm (2016-02-15)
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    the start of each timestep which is then used to obtain the cell by cell properties ACTIVATION IN PHOENICS The HOL method has been implemented in the GX routine GXHOL which is available with PHOENICS It can be activated from PHOENICS VR by selecting Height of Liquid from the Free Surface Models menu of the Models panel of the Main menu Should the user wish to activate HOL by hand from the Q1 the following commands are required In Group 7 STORE DEN1 PRPS SOLVE VFOL VFOL stores the volume fraction of liquid in each cell If there are no inflows i e for a sealed container it is sufficient to STORE VFOL since the solution of VFOL is performed entirely within GXHOL If inflows occur VFOL should be SOLVEd as inlet boundary conditions must be obtained In Group 8 GALA T Activates a volume continuity satisfying flow field TERMS VFOL N N N N P P TERMS ensures that the solution of VFOL is performed in GXHOL In Group 9 The flow properties are calculated in GXPRPS based on the local property marker PRPS PRPS is updated from the VFOL field at the start of every time step No specific settings are needed in Group 9 the PRPS values for the heavy and light fluids are set in Group 19 In Group 11 Initial conditions are required for VFOL and DEN1 for the initial position of the interface Typical settings to place a volume of water in surrounding air would be FIINIT VFOL 0 FIINIT DEN1 1 189 INIADD F PATCH WATER INIVAL IXF IXL IYF IYL IZF IZL ITF ITL INIT WATER VFOL 0 1 INIT WATER DEN1 0 1000 5 It is not necessary to explicitly set PRPS as this is updated internally from the VFOL field In the VR Editor the material for a Blockage object can be set to Light fluid or Heavy fluid In Group 13 Inflow conditions INLET NAME AREA IF IL JF JL KF KL TF TL VALUE NAME P1 VEL RHOM VALUE NAME U1 UIN VALUE NAME V1 VIN VALUE NAME W1 WIN VALUE NAME VFOL 1 RHOM RHOM is the incoming fluid density computed from the rule given in panel 11 In GALA the default source for inflows in the continuity equation is Sv mass inflow cell density If the cell density is different from that of the incoming flow this is not correct GALA will however recognise the inlet value of VFOL and set the source in the continuity equation as Sv mass flow incoming VFOL RHOM Vel 1 RHOM Vel Outflow conditions PATCH NAME AREA IF IL JF JL KF KL TF TL COVAL NAME P1 GRND Pext Fixed pressure conditions are generally applied If the interface crosses the boundary the pressure Coefficient must be replaced with the local value of the density which is done automatically by using GRND as the Coefficient In Group 16 RELAX P2 LINRLX factor Applies a linear relaxation factor to the rate

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_lecs/hollec.htm (2016-02-15)
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    integration domain with dire effects on the subsequent course of the solution Sometimes divergence results from such effects and sometimes a converged solution is arrived at with inflow which differs from the one which corresponds to the situation ostensibly being simulated Of course the belief that the patch should exhibit only outflow may be wrong The patch may comprise several cells through SOME of which fluids flows out while through others it flows in One satisfactory preventive measure is to ascribe physically plausible values of the fluid properties even at outlet boundary condition patches then transitory inflow does no damage Another is so to prescribe the scalar properties of the incoming fluid but NEVER the velocity variables as to make no difference to what prevails in the cell this is effected by way of the command COVAL patchname variable ONLYMS SAME This is indeed highly probable if the third argument of COVAL for P1 is large for then small differences of pressure resulting from the varying dynamic head of the fluid can easily give rise to some cells being above and others below the fourth argument value of the command If this is the case the above mentioned use of SAME in the COVAL commands for other variables will NOT be satisfactory it becomes essential to insert values which are properly representative of the fluid which is drawn in through the patch Should it be desired to eliminate this effect of the variations of dynamic head which can cause non convergence a smaller COVAL coefficient for pressure is required The magnitude of this pressure coefficient Cp is estimated by the following argument The mass flow rate per unit area u is equal to Cp Vp p where Vp is the COVAL value and p is the in cell pressure Hence

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_enc/inad.htm (2016-02-15)
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  • include.htm
    modules are to be re compiled is the sub directory phoenics d includ The files which must be present in this directory for all the options are asapcm bfcear bfcwrk clpcmn cmncvd cmndmn colcmn cvdrad fgemcb gracm1 gracm2 grdbfc grdear

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_enc/include.htm (2016-02-15)
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  • inflow.htm
    COVAL INFLOW H1 FIXVAL H1IN etc Here it should be noted that the mass flow rate is being specified indirectly by way of the value of the velocity U1IN which will prevail at the east side of the first column of cells and by way of the pressure P1IN and enthalpy H1IN which will dictate it is here supposed by way of example the density which is associated with the velocity U1IN This boundary condition prescription takes firmer hold of the values pertaining to the first column of cells than does the one which makes use of ONLYMS it is therefore sometimes preferable An example of this is provided in the following item b Inflow conditions at the circumferential boundary of a cylindrical polar grid The specification of the momentum resolutes to be convected into a polar grid CARTES F at its circumferential boundary necessitates the resolution of the external flow vector into the local directions of u and v These directions change from cell to cell with increasing angle ie increasing IX One approach is to introduce a PATCH for each cell in which the velocity resolutes are set in the 4th argument of COVAL according to the angle between the flow direction and the grid direction A more economical solution is to provide a GROUND sequence which sets all resolutes for a single PATCH that covers the entire zone of inflow Such sequences are provided in subroutine GXPOLR called from Group 13 of GREX3 RSG22 sets the magnitude of the exterior velocity which must be aligned with the radial direction at x 0 GXPOLR is activated separately for u and v by having two PATCHs named UPOL and VPOL For example for inflow over the semi circle extending from NX 4 to 3 NX 4 the following PIL

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_enc/inflow.htm (2016-02-15)
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    NX 4 NY 4 1 3 NY 4 1 1 1 1 INIT MIDDLE H1 0 0 100 0 sets the values of H1 in the centre of the IZ 1 slab to FIINIT H1 100 0 if INIADD T or to 100 0 if INIADD F The default value of INIADD is T Use of this value especially in conjunction with the use of other types than INIVAL permits complex initial value patterns to be created by the use of multiple partly overlapping PATCHes When INIADD F by contrast the effect of any PATCH INIT combination is simply to overwrite the value already set If it is desired to give the variable initial values which vary linearly with x y or z the following steps should be taken the PATCH type should be LINVLX LINVLY or LINVLZ the third argument of INIT should be given the value of the multiplier of x y or z ie the gradient the fourth argument of INIT should be given the value of the additive constant i e the value in the first cell When porosities eg NPOR fields are being set it is important to remember to put FIINIT NPOR 1 0 so that no blockage is present in sections of the domain not identified by PATCH For more complicated variations of the initial fields than those provided by the above options the fourth argument of INIT should be set to GRND This causes EARTH to visit group 11 of GROUND for an array of GROUND set VALues for each cell in the PATCH For example PATCH DOMAIN INIVAL 1 NX 1 NY 1 NZ 1 1 INIT DOMAIN H1 0 0 GRND requires the user to provide in group 11 of GROUND a sequence which fills the EARTH array referred to

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_enc/info.htm (2016-02-15)
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    in X Y and Z defining the block of cells ITF ITL have no significance and should be set to 1 phi is any SOLVEd or STOREd variable value is the value required If it is required to set a different value in each cell of a block then value in the INIT command can be set to one of the ground flags GRND GRND1 GRND10 to activate coding in Group 11 of GROUND The PATCH limits can be set in terms of region numbers by specifying them as IXF IXL etc Initial fields from previous run see PICKUP Initial fields additive or intersecting see INIADD Initial fields printing of see INIFLD Initial guesses Although the final solution is usually independent of the initial guesses supplied via FIINIT or PATCH and INIT by you these guesses can influence both the time taken to attain the solution and indeed whether the solution is reached at all as has been mentioned in sub Section 5 8 above It is therefore a good rule to seek always to supply initial guesses which are as close as possible to the values to be expected in the final solution Thus they should have the right

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