surf_area.F

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!||====================================================================
!||    surf_area   ../engine/source/output/th/surf_area.F
!||--- called by ------------------------------------------------------
!||    hist2       ../engine/source/output/th/hist2.F
!||====================================================================
      SUBROUTINE surf_area(X, NN, SURF_NODES, AREA, NUMNOD)
C-----------------------------------------------
C   I m p l i c i t   T y p e s
C-----------------------------------------------
#include      "implicit_f.inc"
C-----------------------------------------------
C   D u m m y   A r g u m e n t s
C-----------------------------------------------
      INTEGER,INTENT(IN) :: NN,SURF_NODES(NN,4),NUMNOD
      my_real,INTENT(IN) ::  x(3,numnod)
      my_real,INTENT(INOUT) :: area
C-----------------------------------------------
C   L o c a l   V a r i a b l e s
C-----------------------------------------------
      INTEGER I,NOD1,NOD2,NOD3,NOD4
      my_real x13, y13, z13, x24, y24, z24,n1, n2, n3
C-----------------------------------------------
C   S o u r c e   L i n e s
C-----------------------------------------------
      area = zero
      DO i=1,nn
         nod1=surf_nodes(i,1)
         nod2=surf_nodes(i,2)
         nod3=surf_nodes(i,3)
         nod4=surf_nodes(i,4)
         x13= x(1,nod3)-x(1,nod1)
         y13= x(2,nod3)-x(2,nod1)
         z13= x(3,nod3)-x(3,nod1)
         x24= x(1,nod4)-x(1,nod2)
         y24= x(2,nod4)-x(2,nod2)
         z24= x(3,nod4)-x(3,nod2)
         n1 = y13*z24-y24*z13
         n2 = z13*x24-z24*x13
         n3 = x13*y24-x24*y13
         area = area + sqrt(n1*n1+n2*n2+n3*n3)
      ENDDO
      area = area * half
C-----------------------------------------------
      RETURN
      END