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_vel3(ielfa,xrlfa,icyclic,ifatie,gradvfa,
20     &  gradvel,c,ipnei,xxi,nfacea,nfaceb,ncfd)
21!
22!     interpolate/extrapolate the velocity 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     &  i,k,l,indexf,iel1,iel2,ncfd
29!
30      real*8 xrlfa(3,*),gradvfa(3,3,*),gradvel(3,3,*),c(3,3),xxi(3,*),
31     &  xl1,xl2,gradnor
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 k=1,ncfd
46                  do l=1,ncfd
47                     gradvfa(k,l,i)=xl1*gradvel(k,l,iel1)+
48     &                    xl2*gradvel(k,l,iel2)
49                  enddo
50               enddo
51            elseif(ifatie(i).gt.0) then
52               do k=1,ncfd
53                  do l=1,ncfd
54                     gradvfa(k,l,i)=xl1*gradvel(k,l,iel1)+xl2*
55     &                   (c(k,1)*gradvel(1,1,iel2)*c(l,1)+
56     &                    c(k,1)*gradvel(1,2,iel2)*c(l,2)+
57     &                    c(k,1)*gradvel(1,3,iel2)*c(l,3)+
58     &                    c(k,2)*gradvel(2,1,iel2)*c(l,1)+
59     &                    c(k,2)*gradvel(2,2,iel2)*c(l,2)+
60     &                    c(k,2)*gradvel(2,3,iel2)*c(l,3)+
61     &                    c(k,3)*gradvel(3,1,iel2)*c(l,1)+
62     &                    c(k,3)*gradvel(3,2,iel2)*c(l,2)+
63     &                    c(k,3)*gradvel(3,3,iel2)*c(l,3))
64                  enddo
65               enddo
66            else
67               do k=1,ncfd
68                  do l=1,ncfd
69                     gradvfa(k,l,i)=xl1*gradvel(k,l,iel1)+xl2*
70     &                   (c(1,k)*gradvel(1,1,iel2)*c(1,l)+
71     &                    c(1,k)*gradvel(1,2,iel2)*c(2,l)+
72     &                    c(1,k)*gradvel(1,3,iel2)*c(3,l)+
73     &                    c(2,k)*gradvel(2,1,iel2)*c(1,l)+
74     &                    c(2,k)*gradvel(2,2,iel2)*c(2,l)+
75     &                    c(2,k)*gradvel(2,3,iel2)*c(3,l)+
76     &                    c(3,k)*gradvel(3,1,iel2)*c(1,l)+
77     &                    c(3,k)*gradvel(3,2,iel2)*c(2,l)+
78     &                    c(3,k)*gradvel(3,3,iel2)*c(3,l))
79                  enddo
80               enddo
81            endif
82         elseif(ielfa(3,i).gt.0) then
83!
84!           boundary face; no zero gradient
85!
86            do k=1,ncfd
87               do l=1,ncfd
88                  gradvfa(k,l,i)=xl1*gradvel(k,l,iel1)+
89     &                           xrlfa(3,i)*gradvel(k,l,ielfa(3,i))
90               enddo
91            enddo
92         else
93!
94!           boundary face; zero gradient in i-direction
95!
96            indexf=ipnei(iel1)+ielfa(4,i)
97            do k=1,ncfd
98               gradnor=gradvel(k,1,iel1)*xxi(1,indexf)
99     &                +gradvel(k,2,iel1)*xxi(2,indexf)
100     &                +gradvel(k,3,iel1)*xxi(3,indexf)
101               do l=1,ncfd
102                  gradvfa(k,l,i)=gradvel(k,l,iel1)
103     &                          -gradnor*xxi(l,indexf)
104               enddo
105            enddo
106         endif
107      enddo
108c      do i=1,120
109c         write(*,*) 'extrapol_vel3',i,gradvfa(1,1,i),gradvfa(1,2,i)
110c      enddo
111!
112      return
113      end
114