c
c
c
c =================================================
function fdisc(x,y)
c =================================================
implicit double precision (a-h,o-z)
common/cdisc/ x0,y0,xl,alf,beta,r0,idisc
c
c # for computing cell averages for initial data that has a
c # discontinuity along some curve. fdisc should be negative to the
c # left of the curve and positive to the right
c # idisc specifies the nature of the discontinuity for two
c # particular cases (a straight line and circle) but this routine
c # can be modified for any other curve.
c
go to (10,20,30,40) idisc
c
10 continue
c # straight line through (x0,y0) with normal (alf,beta) pointing
c # into right state
c
fdisc = (x-x0)*alf + (y-y0)*beta
return
c
20 continue
c # circle of radius r0:
fdisc = (x-x0)**2 + (y-y0)**2 - r0**2
return
c
30 continue
pi2 = 8.d0*datan(1.d0) !# = 2*pi
c # cosin wave centered at x0,y0 with strenght alf:
fdisc = x-(x0+alf*dcos(pi2*(y-y0)))
return
c
40 continue
pi = 4.d0*datan(1.d0) !# = 2*pi
c # cosin wave centered at x0,y0 with strenght alf:
fdisc = y0-y+alf*dsin(pi*(x-x0)/xl)**2
! fdisc = y0-y
c
return
end