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    associated with the velocity fields within the domain will have little effect If the coefficient is very large by contrast such variations will be effective therefore the magnitude and even the sign of the flow rate will be hard to determine in advance Typically the inflow to a domain is represented by a low coefficient pressure boundary condition whereas an outflow is represented by a high coefficient one but variants are numerous The mass flow source added to the continuity equation is Cp Vp pP where Cp and Vp are the coefficient and value for pressure ie the C and V of the COVAL for P1 The value of the pressure at the nodal point P is denoted by pP e Convective and diffusive sources for j When mass enters a cell from outside the flow domain but not when it leaves the values of all the dependent variables pertaining to the inflowing fluid need to be prescribed The correct effect is achieved by specifying these values as the V s in the correspondi COVAL specification The C s represent the coefficients of the diffu fluxes from the boundary to the nodes in the PATCH The mass flow ra are specified through the pressure boundary condition as explained a The convective and diffusive fluxes of j represented by the above mentioned settings are given by the following expressions for the corresponding source of j Cp Vp pP Vj jP Cj Vj jP for Vp pP ie inflow and Cj Vj jP for Vp pP ie outflow The omission of the convective term for outflow is an expression of the upwind principle and it is analogous to the practice used for the interior coefficient aE see equations 2 4 7 and 2 4 8 To summarize the task is to specify Cp and Vp for pressure P1 and to specify Cj and Vj for the variable j In this way the convective and diffusive fluxes at boundary surfaces are specified Very often the diffusive contribution is zero ie Cj 0 which may also be represented in COVAL by substitution of the word ONLYMS for only mass transfer in its third argument Further information on boundary condition implementation is provided under the COVAL entry in this encylopaedia The entries for PATCH COVAL and SOURCE should be inspected for further information with special attention to the significance which attaches to the use of the arguments FIXVAL FIXFLU ONLYMS FIXP OPPVAL and SAME The keyword commands INLET OUTLET WALL and VALUE can also be used to set the commonly used boundary conditions which correspond to their names f Improved specification of boundary conditions in general menu In Cartesian and cylindrical polar coordinates the location of boundary features inlets outlets blockages etc can now be linked to named objects defined during the grid generation procedure This obviates the need to enter the coordinates twice once when defining the grid and again when specifying boundary conditions as was the case in previous versions If an object

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_enc/boun.htm (2016-02-15)
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    WC1 GRND moving wall UC1E UC1 of east wall VC1E VC1 of east wall WC1E WC1 of east wall UC1W UC1 of west wall VC1W VC1 of west wall WC1W WC1 of west wall UC1N UC1 of north wall VC1N VC1 of north wall WC1N WC1 of north wall UC1S UC1 of south wall VC1S VC1 of south wall WC1S WC1 of south wall UC1H UC1 of high wall VC1H VC1 of high wall WC1H WC1 of high wall UC1L UC1 of low wall VC1L VC1 of low wall WC1L WC1 of low wall iii Turbulent zero slip wall conditions BFC F They are activated by following standart statements WALL SOUTH SOUTH 1 NX 1 1 1 NZ 1 1 COVAL SOUTH UC1 GRND2 UC1WALL COVAL SOUTH WC1 GRND2 WC1WALL iv Turbulent zero slip non moving wall conditions BFC T WALL SOUTH SOUTH 1 NX 1 1 1 NZ 1 1 COVAL SOUTH UC1 GRND GRND COVAL SOUTH VC1 GRND GRND COVAL SOUTH WC1 GRND GRND moving wall UC1E UC1 of east wall VC1E VC1 of east wall WC1E WC1 of east wall UC1W UC1 of west wall VC1W VC1 of west wall WC1W WC1 of west wall UC1N UC1

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_enc/bcond.htm (2016-02-15)
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  • GRDLOC thus COMMON LBFFV P1 P2 U1 U2 V1 V2 W1 W2 R1 R2 RS KE EP H1 H2 1C1 C2 C3 C4 C5 C6 C7 C8 C9 C10 C11 C12 C13 C14 C15 C16 C17 1C18 C19 C20 C21 C22 C23 C24 C25 C26 C27 C28 C29 C30 C31 C32 1C33 C34 C35 The complete GRDLOC file may be inspected via POLIS path 1 4 In an unsteady flow problem the values of dependent variables which pertain to the PREVIOUS time step ie the so called old values are also FFV s Storage is automatically provided for these variables whenever i A SOLVE or SOLUTN command has required that the variable in question shall be solved for and ii the variable STEADY has been set to FALSE and iii a Y appears as the fifth argument of the relevant TERMS command either by direct setting or by default The command SOLVE TEM1 may also be employed so as to activate the direct solution for temperature as distinct from its indirect solution via enthalpy The name TEM1 is recognised within PHOENICS as necessitating the activation of sequences for multiplying by the specific heat see TEM1 for more details c Auxiliary variables FFV s may also be auxiliary variables which are STOREd but not SOLVEd ie those for which N no appears as the third argument of SOLUTN while Y yes appears as the second argument Porosities are of this kind as are those variables which users decide to introduce for their own purposes in GROUND The above example of a STORE command creates storage for two such variables namely HPOR and EFGH Auxiliary variables are not provided with field stores at the previous time step because EARTH has no need for them d Special auxiliary variables SAV s Also to

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_enc/full.htm (2016-02-15)
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    GRNDx EARTH calls the open source subroutine GXIDIF where the following options are supplied by CHAM CINT indvar GRND7 selects the transfer coefficent for INDVAR equal to COI RHO1 ENUL Nuss PRNDTL indvar Dp As where Nuss the Nusselt Number for a sphere As the surface area of the spheres in each cell 6 R2 Volume Dp Dp sphere diameter CINH2C The Nusselt Number for a sphere is taken from equation 5 25 on p 121 and equations E and F of Table 5 4 of Bubbles Drops and Particles by R Clift JR Grace and ME Weber The minimum slip velocity used in the Reynolds Number calculation is CINH1C The correlation for the transfer coefficient assumes bulk to bulk transfer so the PHINTs for both phases should be left at their default value The CINT of the continuous or carrier phase should be set to GRND7 whereas the CINT for the dispersed phase should be set to a very large number say 1 0E10 see the entry on PHINT for an explanation In the case of heat transfer these settings are appropriate for constant and equal phase specific heats i e CP1 CP2 For constant and different phase specific

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_enc/cint.htm (2016-02-15)
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    minimizes the user s data input actions 2 2 The macros a gravity This PIL fragment is to be found in file d earth d core inplib 074 htm It is activated by the command gravity because the character variable gravity has been declared as L074 in PIL fragment 14 This macro declares some further variables for later use namely DENSITY 075 DENSDIFF 076 BOUSS 077 EXTBOUSS 079 BUOY 078 Then it makes some preliminary settings and prints out some messages The four PIL fragments may be seen by clicking here density densdiff bouss and extbouss They make the ground number settings needed for activation of sequences in the subroutine GXBUOYSO they then load PIL fragment buoy The reason for including the start of and end of lines is that when these macros are used in interactive mode and the answer yes is given to the copy to Q1 question the content of the macros is included in the new Q1 file Some users like subsequently to remove them by editing replacing them by the original commands The start and end markers assist this cleaning out process b PIL fragment buoy The functions of the buoy PIL fragment are to define the whole domain BUOYANCY patch to provide the corresponding COVAL statements for the relevant velocities and to set appropriate values for the PIL variables BUOYA BUOYB BUOYC BUOYD and BUOYE which play their parts in the coding of subroutine GXBUOYSO The PIL fragment buoy responds to the previously made settings of buoyopt gravdir rhoref tref href CARTES BFC NX NY NZ as well as to whether the temperature or the enthalpy is the energy equation variable and to whether fluid properties are being obtained by way the settings of the PRPS variable and its references to the PROPS file in sub directory d EARTH 2 3 Other means The macros as explained above are convenient means of writing PIL statements which will then activate coding sequences to be found in subroutine GXBUOYSO However it is not necessary to use them and users who wish to have control of every move may prefer to make direct settings themselves The present section of this article is for such users The sequences in GXBUOYSO are entered when a PATCH is defined with a name beginning with the letters BUOY either upper or lower case When direct settings are created by the user however any other non reserved name may be used For cartesian coordinates and for cylindrical polar coordinates when the z axis is vertical gravity sources of the form of equation 1 above can be inserted via PATCH and COVAL statements as follows PATCH GRAVITY PHASEM 1 NX 1 NY 1 NZ 1 LSTEP followed if the z direction is vertically upwards by COVAL GRAVITY W1 FIXFLU 9 81 In two phase flows the following additional specification would be required COVAL GRAVITY W2 FIXFLU 9 81 For cartesian coordinates only if it is the x or y directions which are vertically

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_enc/grav.htm (2016-02-15)
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    code The interface is a translator which will read an ASCII format IGES wire frame model and write the geometry into a PHOENICS Q1 file This will provide the user with the initial data for the development of a grid using the interactive grid generation facilities within the PHOENICS menu system IGES ENTITIES TRANSFERRED IGES Entity No IGES Entity Name PHOENICS Entity 100 Circular Arc ARC Line 102 Composite curve

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_enc/cad.htm (2016-02-15)
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    Vol i e as compared with the previous case it uses the phase 2 density rather than that of phase 1 Dimensions of FRICCO and C are as before CFIPS GRND causes EARTH to call the open source GROUND subroutine of PHOENICS where it expects to find coding supplied by the user for calculating values of FRICCO cell by cell CFIPS GRND1 GRND2 GRND10 causes EARTH to call open source GXIFRIC HTM GROUND subroutine of PHOENICS and so to take one of the following options supplied by CHAM according to which CFIPS GRND1 selects FRICCO CFIPC M1 R2 where M1 is the phase 1 mass in the cell and R2 is the phase 2 volume fraction CFIPC has units of Newton seconds kg meter CFIPS GRND2 selects FRICCO CFIPC M1 R2 max relspeed CFIPA where relspeed is the relative speed between the phases CFIPC has units of Newton seconds 2 kg meter 2 CFIPA has units of meter second CFIPS GRND3 selects FRICCO CFIPC M1 R2 max relspeed CFIPA CFIPB CFIPC has units of Newton seconds 2 kg meter 2 CFIPA has units of meter second CFIPB is a dimensionless exponent often chosen as 2 0 CFIPS GRND4 selects FRICCO CFIPC M1 R2 max relspeed CFIPA CFIPB EL1 CFIPD CFIPS GRND5 selects FRICCO CFIPC M2 R1 max relspeed CFIPA CFIPB EL1 CFIPD where M2 is the phase 2 mass in the cell and R1 is the phase 1 volume fraction CFIPS GRND6 selects FRICCO CFIPC Vol CFIPS GRND7 selects the dispersed flow model FRICCO 0 75 Cd RHO1 R2 R1 Vol max relspeed CFIPA CFIPB wherein phase 1 is the carrier and phase 2 is dispersed Cd is a dimensionless drag coefficient CFIPB is the particle diameter CFIPD selects the correlation employed for Cd as described below CFIPS GRND8 selects

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_enc/cfips.htm (2016-02-15)
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    CH3 XXX CH3 CH1 CH1 QQQ CH2 is equivalent to CH3 CH1XXXQQQXXXZZ The values of individual variables can be ascertained by typing the variable name as with integers and reals Alternatively typing SEE C gives the values of all currently declared character variables Expression Substitution Character variable names placed between colons have their values substituted for their names This process is actually carried out at a pre processing stage and applies to integer and real expressions a well as character variable names It therefore has more power than merely allowing string concatenation as will now be illustrated The following two PIL statements are exactly equivalent NX 4 PATCH INL NX NORTH 1 NX 1 NY 1 1 1 1 NX 4 PATCH INL4 NORTH 1 4 1 NY 1 1 1 1 This feature can be used to set real or integer variables from character variables as shown below REAL RR CHAR CC CC 4 5 RR CC XFRAC 4 RR However RR CC would elicit an Invalid variable message Case and special characters PIL commands are usually upper cased and compressed to remove all spaces before processing This means that unless avoiding action is taken character strings may not

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