Merge pull request #14176 from drjfloyd/master

FDS Source: fix circle rectangle chord only intersection area Issue #…

Author: drjfloyd

Source/func.f90

@@ -9299,25 +9299,25 @@ REAL(EB) FUNCTION CIRCLE_CELL_INTERSECTION_AREA(X0,Y0,RAD,X1,X2,Y1,Y2)
    CASE (0)
       ! First four cases are more than half the cirlce outside the rectangle.
       ! Can only have one edge where this is the case without having a corner inside. This edge makes a chord.
-      ! Intersection area is the circle area minus the area of the chord.
+      ! Intersection area is the area of the chord.
       IF (X2 <= X0 .AND. X2 > X0-RAD) THEN
          THETA = 2._EB*ACOS((X0-X2)/RAD)         
-         CIRCLE_CELL_INTERSECTION_AREA = R2*(PI - 0.5_EB*(THETA-SIN(THETA)))
+         CIRCLE_CELL_INTERSECTION_AREA = 0.5_EB*(THETA-SIN(THETA))
          RETURN
       ENDIF
       IF (Y2 <= Y0 .AND. Y2 > Y0-RAD) THEN
          THETA = 2._EB*ACOS((Y0-Y2)/RAD)         
-         CIRCLE_CELL_INTERSECTION_AREA = R2*(PI - 0.5_EB*(THETA-SIN(THETA)))
+         CIRCLE_CELL_INTERSECTION_AREA = 0.5_EB*(THETA-SIN(THETA))
          RETURN
       ENDIF
       IF (X1 >= X0 .AND. X1 < X0+RAD) THEN
          THETA = 2._EB*ACOS((X1-X0)/RAD)         
-         CIRCLE_CELL_INTERSECTION_AREA = R2*(PI - 0.5_EB*(THETA-SIN(THETA)))
+         CIRCLE_CELL_INTERSECTION_AREA = 0.5_EB*(THETA-SIN(THETA))
          RETURN
       ENDIF
       IF (Y1 >= Y0 .AND. Y1 < Y0+RAD) THEN
          THETA = 2._EB*ACOS((X1-X0)/RAD)         
-         CIRCLE_CELL_INTERSECTION_AREA = R2*(PI - 0.5_EB*(THETA-SIN(THETA)))
+         CIRCLE_CELL_INTERSECTION_AREA = 0.5_EB*(THETA-SIN(THETA))
          RETURN
       ENDIF
       ! Remaining cases is where one or more rectangle edges are inside but the corners are outside