subroutine stflow(uf,vf,px,py,nx,ny)
***********************************************************
c
c     initialize the flow by specifying the velocity and
c     set pressure to zero.
c
c     uf,vf        <-      initial value to be set
c
c**********************************************************
      integer i,j,nx,ny,nxm,nym,mxym
      include 'gridsz'
      double precision uf(nx,ny),vf(nx,ny),px(nx,ny),py(nx,ny)
      double precision h,hinv,x,y,pi,uby,vby,utop,ubot
      common/meshsz/h,hinv
      common/uvboud/uby(nym),vby(nym),utop,ubot
c     ******************************************************
      pi = 4.D0*datan(1.D0)

      do 5 j=1,ny
         y = (dble(j)-0.5D0)*h
      do 5 i=1,nx
         x = (dble(i)-0.5D0)*h
         uf(i,j) = 0.D0
         vf(i,j) = 0.D0
         px(i,j) = 0.D0
         py(i,j) = 0.D0
 5    continue
      do 6 j=1,ny
         uby(j) = 0.D0
         vby(j) = 0.D0
 6    continue
      utop = 0.D0
      ubot = 0.D0
*     *****************************************************

      end