!-------------------------------------------------------------------------------

!                      Code_Saturne version 2.0.4n!                      --------------------------

!     This file is part of the Code_Saturne Kernel, element of the
!     Code_Saturne CFD tool.

!     Copyright (C) 1998-2009 EDF S.A., France

!     contact: saturne-support@edf.fr

!     The Code_Saturne Kernel is free software; you can redistribute it
!     and/or modify it under the terms of the GNU General Public License
!     as published by the Free Software Foundation; either version 2 of
!     the License, or (at your option) any later version.

!     The Code_Saturne Kernel is distributed in the hope that it will be
!     useful, but WITHOUT ANY WARRANTY; without even the implied warranty
!     of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
!     GNU General Public License for more details.

!     You should have received a copy of the GNU General Public License
!     along with the Code_Saturne Kernel; if not, write to the
!     Free Software Foundation, Inc.,
!     51 Franklin St, Fifth Floor,
!     Boston, MA  02110-1301  USA

!-------------------------------------------------------------------------------

subroutine ustssc &
!================

 ( idbia0 , idbra0 ,                                              &
   ndim   , ncelet , ncel   , nfac   , nfabor , nfml   , nprfml , &
   nnod   , lndfac , lndfbr , ncelbr ,                            &
   nvar   , nscal  , nphas  , ncepdp , ncesmp ,                   &
   nideve , nrdeve , nituse , nrtuse , iscal  ,                   &
   ifacel , ifabor , ifmfbr , ifmcel , iprfml , maxelt , lstelt , &
   ipnfac , nodfac , ipnfbr , nodfbr , icepdc , icetsm , itypsm , &
   idevel , ituser , ia     ,                                     &
   xyzcen , surfac , surfbo , cdgfac , cdgfbo , xyznod , volume , &
   dt     , rtpa   , rtp    , propce , propfa , propfb ,          &
   coefa  , coefb  , ckupdc , smacel ,                            &
   crvexp , crvimp ,                                              &
   viscf  , viscb  , xam    ,                                     &
   w1     , w2     , w3     , w4     , w5     ,                   &
   w6     , w7     , w8     , w9     , w10    , w11    ,          &
   rdevel , rtuser , ra     )

!===============================================================================
! Purpose:
! -------

!    User subroutine.

!    Additional right-hand side source terms for scalar equations (user
!     scalars and specific physics scalars).

!
! Usage
! -----
! The routine is called for each scalar, user or specific physisc. It is
! therefore necessary to test the value of the scalar number iscal to separate
! the treatments of the different scalars (if (iscal.eq.p) then ....).
!
! The additional source term is decomposed into an explicit part (crvexp) and
! an implicit part (crvimp) that must be provided here.
! The resulting equation solved by the code for a scalar f is:
!
!  rho*volume*df/dt + .... = crvimp*f + crvexp
!
!
! Note that crvexp and crvimp are defined after the Finite Volume integration
! over the cells, so they include the "volume" term. More precisely:
!   - crvexp is expressed in kg.[scal]/s, where [scal] is the unit of the scalar
!   - crvimp is expressed in kg/s
!
!
! The crvexp and crvimp arrays are already initialized to 0 before entering the
! the routine. It is not needed to do it in the routine (waste of CPU time).
!
! For stability reasons, Code_Saturne will not add -crvimp directly to the
! diagonal of the matrix, but Max(-crvimp,0). This way, the crvimp term is
! treated implicitely only if it strengthens the diagonal of the matrix.
! However, when using the second-order in time scheme, this limitation cannot
! be done anymore and -crvimp is added directly. The user should therefore test
! the negativity of crvimp by himself.
!
! When using the second-order in time scheme, one should supply:
!   - crvexp at time n
!   - crvimp at time n+1/2
!
!
! The selection of cells where to apply the source terms is based on a getcel
! command. For more info on the syntax of the getcel command, refer to the
! user manual or to the comments on the similar command getfbr in the routine
! usclim.

!
! STEEP SOURCE TERMS
!===================
! In case of a complex, non-linear source term, say F(f), for scalar f, the
! easiest method is to implement the source term explicitely.
!
!   df/dt = .... + F(f(n))
!   where f(n) is the value of f at time tn, the befinning of the time step.
!
! This yields :
!   crvexp = volume*F(f(n))
!   crvimp = 0
!
! However, if the source term is potentially steep, this fully explicit
! method will probably generate instabilities. It is therefore wiser to
! partially implicit the term by writing:
!
!   df/dt = .... + dF/df*f(n+1) - dF/df*f(n) + F(f(n))
!
! This yields:
!   crvexp = volume*( F(f(n)) - dF/df*f(n) )
!   crvimp = volume*dF/df

!-------------------------------------------------------------------------------
! Arguments
!__________________.____._____.________________________________________________.
! name             !type!mode ! role                                           !
!__________________!____!_____!________________________________________________!
! idbia0           ! i  ! <-- ! number of first free position in ia            !
! idbra0           ! i  ! <-- ! number of first free position in ra            !
! ndim             ! i  ! <-- ! spatial dimension                              !
! ncelet           ! i  ! <-- ! number of extended (real + ghost) cells        !
! ncel             ! i  ! <-- ! number of cells                                !
! nfac             ! i  ! <-- ! number of interior faces                       !
! nfabor           ! i  ! <-- ! number of boundary faces                       !
! nfml             ! i  ! <-- ! number of families (group classes)             !
! nprfml           ! i  ! <-- ! number of properties per family (group class)  !
! nnod             ! i  ! <-- ! number of vertices                             !
! lndfac           ! i  ! <-- ! size of nodfac indexed array                   !
! lndfbr           ! i  ! <-- ! size of nodfbr indexed array                   !
! ncelbr           ! i  ! <-- ! number of cells with faces on boundary         !
! nvar             ! i  ! <-- ! total number of variables                      !
! nscal            ! i  ! <-- ! total number of scalars                        !
! nphas            ! i  ! <-- ! number of phases                               !
! ncepdp           ! i  ! <-- ! number of cells with head loss terms           !
! ncssmp           ! i  ! <-- ! number of cells with mass source terms         !
! nideve, nrdeve   ! i  ! <-- ! sizes of idevel and rdevel arrays              !
! nituse, nrtuse   ! i  ! <-- ! sizes of ituser and rtuser arrays              !
! iscal            ! i  ! <-- ! index number of the current scalar             !
! ifacel(2, nfac)  ! ia ! <-- ! interior faces -> cells connectivity           !
! ifabor(nfabor)   ! ia ! <-- ! boundary faces -> cells connectivity           !
! ifmfbr(nfabor)   ! ia ! <-- ! boundary face family numbers                   !
! ifmcel(ncelet)   ! ia ! <-- ! cell family numbers                            !
! iprfml           ! ia ! <-- ! property numbers per family                    !
!  (nfml, nprfml)  !    !     !                                                !
! maxelt           ! i  ! <-- ! max number of cells and faces (int/boundary)   !
! lstelt(maxelt)   ! ia ! --- ! work array                                     !
! ipnfac(nfac+1)   ! ia ! <-- ! interior faces -> vertices index (optional)    !
! nodfac(lndfac)   ! ia ! <-- ! interior faces -> vertices list (optional)     !
! ipnfbr(nfabor+1) ! ia ! <-- ! boundary faces -> vertices index (optional)    !
! nodfbr(lndfbr)   ! ia ! <-- ! boundary faces -> vertices list (optional)     !
! icepdc(ncepdp)   ! ia ! <-- ! index number of cells with head loss terms     !
! icetsm(ncesmp)   ! ia ! <-- ! index number of cells with mass source terms   !
! itypsm           ! ia ! <-- ! type of mass source term for each variable     !
!  (ncesmp,nvar)   !    !     !  (see ustsma)                                  !
! idevel(nideve)   ! ia ! <-- ! integer work array for temporary developpement !
! ituser(nituse    ! ia ! <-- ! user-reserved integer work array               !
! ia(*)            ! ia ! --- ! main integer work array                        !
! xyzcen           ! ra ! <-- ! cell centers                                   !
!  (ndim, ncelet)  !    !     !                                                !
! surfac           ! ra ! <-- ! interior faces surface vectors                 !
!  (ndim, nfac)    !    !     !                                                !
! surfbo           ! ra ! <-- ! boundary faces surface vectors                 !
!  (ndim, nfavor)  !    !     !                                                !
! cdgfac           ! ra ! <-- ! interior faces centers of gravity              !
!  (ndim, nfac)    !    !     !                                                !
! cdgfbo           ! ra ! <-- ! boundary faces centers of gravity              !
!  (ndim, nfabor)  !    !     !                                                !
! xyznod           ! ra ! <-- ! vertex coordinates (optional)                  !
!  (ndim, nnod)    !    !     !                                                !
! volume(ncelet)   ! ra ! <-- ! cell volumes                                   !
! dt(ncelet)       ! ra ! <-- ! time step (per cell)                           !
! rtpa             ! ra ! <-- ! calculated variables at cell centers           !
!  (ncelet, *)     !    !     !  (preceding time step)                         !
! rtp              ! ra ! <-- ! calculated variables at cell centers           !
!  (ncelet, *)     !    !     !  (current time step)                           !
! propce(ncelet, *)! ra ! <-- ! physical properties at cell centers            !
! propfa(nfac, *)  ! ra ! <-- ! physical properties at interior face centers   !
! propfb(nfabor, *)! ra ! <-- ! physical properties at boundary face centers   !
! coefa, coefb     ! ra ! <-- ! boundary conditions                            !
!  (nfabor, *)     !    !     !                                                !
! ckupdc(ncepdp,6) ! ra ! <-- ! head loss coefficient                          !
! smacel           ! ra ! <-- ! value associated to each variable in the mass  !
!  (ncesmp,nvar)   !    !     !  source terms or mass rate (see ustsma)        !
! crvexp           ! ra ! --> ! explicit part of the source term               !
! crvimp           ! ra ! --> ! implicit part of the source term               !
! viscf(nfac)      ! ra ! --- ! work array                                     !
!  viscb(nfabor)   ! ra ! --- ! work array                                     !
! xam(nfac,2)      ! ra ! --- ! work array                                     !
! w1 to w11(ncelet)! ra ! --- ! work arrays                                    !
! rdevel(nrdeve)   ! ra ! <-> ! real work array for temporary developpement    !
! rtuser(nituse    ! ra ! <-- ! user-reserved real work array                  !
! ra(*)            ! ra ! --- ! main real work array                           !
!__________________!____!_____!________________________________________________!

!     Type: i (integer), r (real), s (string), a (array), l (logical),
!           and composite types (ex: ra real array)
!     mode: <-- input, --> output, <-> modifies data, --- work array
!===============================================================================

implicit none

!===============================================================================
! Common blocks
!===============================================================================

include "paramx.h"
include "pointe.h"
include "numvar.h"
include "entsor.h"
include "optcal.h"
include "cstphy.h"
include "parall.h"
include "period.h"

!===============================================================================

! Arguments

integer          idbia0 , idbra0
integer          ndim   , ncelet , ncel   , nfac   , nfabor
integer          nfml   , nprfml
integer          nnod   , lndfac , lndfbr , ncelbr
integer          nvar   , nscal  , nphas
integer          ncepdp , ncesmp
integer          nideve , nrdeve , nituse , nrtuse
integer          iscal

integer          ifacel(2,nfac) , ifabor(nfabor)
integer          ifmfbr(nfabor) , ifmcel(ncelet)
integer          iprfml(nfml,nprfml)
integer          maxelt, lstelt(maxelt)
integer          ipnfac(nfac+1), nodfac(lndfac)
integer          ipnfbr(nfabor+1), nodfbr(lndfbr)
integer          icepdc(ncepdp)
integer          icetsm(ncesmp), itypsm(ncesmp,nvar)
integer          idevel(nideve), ituser(nituse), ia(*)

double precision xyzcen(ndim,ncelet)
double precision surfac(ndim,nfac), surfbo(ndim,nfabor)
double precision cdgfac(ndim,nfac), cdgfbo(ndim,nfabor)
double precision xyznod(ndim,nnod), volume(ncelet)
double precision dt(ncelet), rtp(ncelet,*), rtpa(ncelet,*)
double precision propce(ncelet,*)
double precision propfa(nfac,*), propfb(nfabor,*)
double precision coefa(nfabor,*), coefb(nfabor,*)
double precision ckupdc(ncepdp,6), smacel(ncesmp,nvar)
double precision crvexp(ncelet), crvimp(ncelet)
double precision viscf(nfac), viscb(nfabor)
double precision xam(nfac,2)
double precision w1(ncelet), w2(ncelet), w3(ncelet)
double precision w4(ncelet), w5(ncelet), w6(ncelet)
double precision w7(ncelet), w8(ncelet), w9(ncelet)
double precision w10(ncelet), w11(ncelet)
double precision rdevel(nrdeve), rtuser(nrtuse), ra(*)

! Local variables

character*80     chaine
integer          idebia, idebra
integer          ivar, iiscvr, ipcrom, iel, iphas, iutile
integer          ilelt, nlelt

double precision tauf, prodf, volf, pwatt

!===============================================================================



!===============================================================================
! 1. Initialization
!===============================================================================

idebia = idbia0
idebra = idbra0

! --- Index number of the variable associated to scalar iscal
ivar = isca(iscal)

! --- Name of the the variable associated to scalar iscal
chaine = nomvar(ipprtp(ivar))

! --- Indicateur of variance scalars
!         If iscavr(iscal) = 0:
!           the scalar iscal is not a variance
!         If iscavr(iscal) > 0 and iscavr(iscal) < nscal + 1 :
!           the scalar iscal is the variance of the scalar iscavr(iscal)
iiscvr = iscavr(iscal)

! --- Index number of the phase associated to scalar iscal
iphas = iphsca(iscal)

! --- Index number of the density in the propce array
ipcrom = ipproc(irom(iphas))

if(iwarni(ivar).ge.1) then
  write(nfecra,1000) chaine(1:8)
endif


!===============================================================================
! 2. Example of arbitrary source term for the scalar f, 2nd scalar in the
!    calculation

!                             S = A * f + B

!            appearing in the equation under the form

!                       rho*df/dt = S (+ regular terms in the equation)


!In the following example:
!     A = - rho / tauf
!     B =   rho * prodf
!        AVEC
!     tauf   = 10.d0  [ s  ] (dissipation time for f)
!     prodf  = 100.d0 [ [f]/s ] (production of f by unit of time)

!which yields
!     crvimp(iel) = volume(iel)* A = - volume(iel)*rho/tauf
!     crvexp(iel) = volume(iel)* B =   volume(iel)*rho*prodf

!===============================================================================


! ----------------------------------------------

! It is quite frequent to forget to remove this example when it is
!  not needed. Therefore the following test is designed to prevent
!  any bad surprise.

iutile = 0

if(iutile.eq.0) return

! ----------------------------------------------

!Source term applied to second scalar
if (iscal.eq.2) then

   tauf  = 10.d0
   prodf = 100.d0

   do iel = 1, ncel
      crvimp(iel) = - volume(iel)*propce(iel,ipcrom)/tauf
   enddo

   do iel = 1, ncel
      crvexp(iel) =   volume(iel)*propce(iel,ipcrom)*prodf
   enddo

endif

!===============================================================================
! 3. Example of arbitrary volumic heat term in the equation for enthalpy h

! In the considered example, a uniform volumic source of heating is imposed
! in the cells with coordinate X in [0;1.2] and Y in [3.1;4]

! The global heating power if Pwatt (in W) and the total volume of the concerned
! cells is volf (in m3)

! This yields
!     crvimp(iel) = 0
!     crvexp(iel) = volume(iel)* Pwatt/volf

!===============================================================================


! ----------------------------------------------

! It is quite frequent to forget to remove this example when it is
!  not needed. Therefore the following test is designed to prevent
!  any bad surprise.

iutile = 0

if(iutile.eq.0) return

! ----------------------------------------------

! WARNING :
! It is assumed here that the thermal scalar in an enthalpy.
!  If the scalar in a temperature, PWatt must be devided by Cp.

pwatt = 100.d0

! calculation of volf

volf  = 0.d0
CALL GETCEL('X > 0.0 and X < 1.2 and Y > 3.1 and'//               &
            'Y < 4.0',NLELT,LSTELT)

do ilelt = 1, nlelt
  iel = lstelt(ilelt)
  volf = volf + volume(iel)
enddo

do ilelt = 1, nlelt
  iel = lstelt(ilelt)
! No implicit source term
  crvimp(iel) = 0.d0
! Explicit source term
  crvexp(iel) = volume(iel)*pwatt/volf
enddo

!--------
! Formats
!--------

 1000 format(' User source terms for vaiable ',A8,/)

!----
! End
!----

return

