1!
2!     CalculiX - A 3-dimensional finite element program
3!              Copyright (C) 1998-2021 Guido Dhondt
4!
5!     This program is free software; you can redistribute it and/or
6!     modify it under the terms of the GNU General Public License as
7!     published by the Free Software Foundation(version 2);
8!
9!
10!     This program is distributed in the hope that it will be useful,
11!     but WITHOUT ANY WARRANTY; without even the implied warranty of
12!     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13!     GNU General Public License for more details.
14!
15!     You should have received a copy of the GNU General Public License
16!     along with this program; if not, write to the Free Software
17!     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
18!
19      subroutine extrapol_tel3(ielfa,xrlfa,icyclic,ifatie,gradtfa,
20     &  gradtel,c,ipnei,xxi,ifabou,xxn,xload,nfacea,nfaceb,ncfd)
21!
22!     interpolate/extrapolate the temperature gradient from the
23!     center of the elements to the center of the faces
24!
25      implicit none
26!
27      integer ielfa(4,*),icyclic,ifatie(*),ipnei(*),nfacea,nfaceb,
28     &  iel1,iel2,i,l,indexf,ifabou(*),ncfd
29!
30      real*8 xrlfa(3,*),gradtfa(3,*),gradtel(3,*),c(3,3),xxi(3,*),
31     &  gradnor,xl1,xl2,q,xxn(3,*),xload(2,*)
32!
33!
34!
35      do i=nfacea,nfaceb
36         iel1=ielfa(1,i)
37         xl1=xrlfa(1,i)
38         iel2=ielfa(2,i)
39         if(iel2.gt.0) then
40!
41!           face between two elements
42!
43            xl2=xrlfa(2,i)
44            if((icyclic.eq.0).or.(ifatie(i).eq.0)) then
45               do l=1,ncfd
46                  gradtfa(l,i)=xl1*gradtel(l,iel1)+
47     &                 xl2*gradtel(l,iel2)
48               enddo
49            elseif(ifatie(i).gt.0) then
50               do l=1,ncfd
51                  gradtfa(l,i)=xl1*gradtel(l,iel1)+xl2*
52     &                  (gradtel(1,iel2)*c(l,1)+
53     &                   gradtel(2,iel2)*c(l,2)+
54     &                   gradtel(3,iel2)*c(l,3))
55               enddo
56            else
57               do l=1,ncfd
58                  gradtfa(l,i)=xl1*gradtel(l,iel1)+xl2*
59     &                  (gradtel(1,iel2)*c(1,l)+
60     &                   gradtel(2,iel2)*c(2,l)+
61     &                   gradtel(3,iel2)*c(3,l))
62               enddo
63            endif
64         elseif(ielfa(3,i).gt.0) then
65!
66!           the above condition implies iel2!=0
67!           if iel2 were zero, no b.c. would apply and
68!           ielfa(3,i) would be zero or negative
69!
70!           boundary face; no zero gradient
71!
72            if(ifabou(-iel2).gt.0) then
73!
74!              temperature given: extrapolate gradient
75!
76               do l=1,ncfd
77                  gradtfa(l,i)=xl1*gradtel(l,iel1)+
78     &                 xrlfa(3,i)*gradtel(l,abs(ielfa(3,i)))
79               enddo
80            else
81!
82!              facial temperature gradient given, may be nonzero
83!
84               indexf=ipnei(iel1)+ielfa(4,i)
85!
86               if(ifabou(-iel2+6).eq.0) then
87                  q=0.d0
88               else
89                  q=xload(1,ifabou(-iel2+6))
90               endif
91               gradnor=gradtel(1,iel1)*xxn(1,indexf)
92     &                +gradtel(2,iel1)*xxn(2,indexf)
93     &                +gradtel(3,iel1)*xxn(3,indexf)-q
94               do l=1,ncfd
95                  gradtfa(l,i)=gradtel(l,iel1)
96     &                        -gradnor*xxn(l,indexf)
97               enddo
98            endif
99         else
100!
101!           boundary face; zero gradient
102!
103            indexf=ipnei(iel1)+ielfa(4,i)
104            gradnor=gradtel(1,iel1)*xxi(1,indexf)+
105     &              gradtel(2,iel1)*xxi(2,indexf)+
106     &              gradtel(3,iel1)*xxi(3,indexf)
107            do l=1,ncfd
108                  gradtfa(l,i)=gradtel(l,iel1)
109     &                        -gradnor*xxi(l,indexf)
110            enddo
111         endif
112      enddo
113!
114      return
115      end
116