Stream function by Relaxation Tecnique in fortran

c Program to find Stream function by Relaxation Tecnique

dimension u(10,10),v(10,10),vort(10,10),ngrid(10,10),ogrid(10,10)
real forcef,ngrid,ogrid,residue
integer n,k

print*,'Enter the size of grid excluding boundary:'
read*,n
print*,'Enter the distance between grid points :'
read*,d


do i=1,n+2
u(1,i)=0
u(i,1)=0
u(n+2,i)=0
u(i,n+2)=0
v(1,i)=0
v(i,1)=0
v(n+2,i)=0
v(i,n+2)=0
vort(1,i)=0
vort(i,1)=0
vort(n+2,i)=0
vort(i,n+2)=0
ngrid(1,i)=0
ngrid(i,1)=0
ngrid(n+2,i)=0
ngrid(i,n+2)=0
ogrid(1,i)=0
ogrid(i,1)=0
ogrid(n+2,i)=0
ogrid(i,n+2)=0
enddo

open (1,file='uwnd.dat')
read (1,*)((u(i,j),j=2,n+1),i=2,n+1)
close(1)
open (2,file='vwnd.dat')
read (2,*)((v(i,j),j=2,n+1),i=2,n+1)
close(2)
do i=2,n+1
do j=2,n+1
vort(i,j)=((v(i+1,j)-v(i-1,j))-(u(i,j+1)-u(i,j-1)))/(2*d)
enddo
enddo

write(*,*)'Vorticity values'
do i=2,n+1
write(*,*) (vort(i,j),j=2,n+1)
enddo

do i=2,n+1
do j=2,n+1
ngrid(i,j)=0
enddo
enddo

k=1
10 print*,'Trial :',k

do i=2,n+1
do j=2,n+1
ogrid(i,j)=ngrid(i,j)
enddo
enddo

do i=2,n+1
do j=2,n+1
residue=ogrid(i-1,j)+ogrid(i+1,j)+ogrid(i,j-1)+ogrid(i,j+1)-(4*ogrid(i,j))+(d*d*vort(i,j))

ngrid(i,j)=ogrid(i,j)+(residue/4)
enddo
enddo

do i=2,n+1
do j=2,n+1
if((ngrid(i,j)-ogrid(i,j)).gt.0.0001) then
k=k+1
goto 10
endif
enddo
enddo


open(3,file="stream_function.txt")
do i=2,n+1
write(3,*) (ngrid(i,j),j=2,n+1)
enddo
write(*,*)'Stream function values are written in the file stream_function.txt'
do i=2,n+1
write(*,*) (ngrid(i,j),j=2,n+1)
enddo
stop
end