CINT

------ PIL real array; default=1.0; group 10,

CINT(phi) concerns inter-phase diffusion in two-phase flow simulations.

If CINT(phi) has a positive value, the bulk-to-interface diffusion coefficient for the variable phi is equal to that value times the reference interface coefficient set by way of CFIPS.
It is in this case a dimensionless multiplication factor.

If CINT(phi) has a negative value other than GRND or GRNDx the bulk-to-interface diffusion coefficient for the variable phi is equal to the negative of that value.
Its dimensions are then transfer rate per unit volume divided by phi-difference.

If CINT is set equal to GRND, EARTH calls GROUP 10 of GROUND, where it expects to find an array of interphase-coefficient values computed by coding introducd by the user.

If CINT is set equal to 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 heats, phase 1 must be taken as the continuous phase and PHINT(H1)=CP1/CP2 (again see the PHINT entry for an explanation).

  In the case of heat-transfer, the correlations assume that the bulk values are temperatures, not enthalpies.

  If the shadow volume fraction, RS, is SOLVEd, the diameter is taken as CINH2C*(R2/RS)**2.

  STORE(NUSS) causes the Nusselt Number to be stored.

  NOTE - If this option is used together with CFIPS = GRND7 or GRND8, the STORED diameter (STORE(SIZE)) will be used instead of CINH2C, and the STORED slip velocity (STORE(VREL)) will also be used if present.

• CINT(indvar) = GRND8 selects the same form of transfer coefficient as GRND7, except that the Nusselt Number is calculated from the Ranz-Marshall correlation,
  Nu = 2 + 0.6*Pr**0.333*Re**0.5

  See CFIPS and PHINT for further information.