on unconvincing results for channel flow simulatio

yf yap

i am doing a simulation on steady, viscous, incompressible flow through a curved channel. the NS equations are parabolized. the solution is marched in the streamwise (from station n to n+1) direction using the ADI method. after imposing the required boundary conditions, and the solution for the n=2,3,4,.. plane are obtained. the boundary conditions are: 1) uniform inlet velocity (streamwise) 2) tranverse velocity =0 (inlet)(r and z, cylindrical coordinate system is used, n being the streamwise direction) 3) at the channel wall, u=v=w=0 (u in r direction, v in z direction and w in the streamwise direction,n) however, the results that i obtained is not convincing at all. for a given plane(n>=2), the streamwise velocity that i obtained for any grid point immediately adjacent to the wall is almost equal, and sometime, even larger than the inlet velocity, that is the streamwise velocity is impulsively increased form zero at the wall to almost equal to the inlet velocity, which is not true. below is one of the results that i obtained.(lower left corner of the channel) the streamwise inlet velocity=1.0

magnitude of the streamwise velocity 0 0.974201 0.975 0.975 0.975 0.975 0 0.974201 0.975 0.975 0.975 0.975 0 0.974201 0.975 0.975 0.975 0.975 0 0.974201 0.975 0.975 0.975 0.975 0 0.974201 0.975 0.975 0.975 0.975 0 0.974201 0.975 0.975 0.975 0.975 0 0.974201 0.975 0.975 0.975 0.975 0 0.974201 0.975 0.975 0.975 0.975 0 0.974201 0.975 0.975 0.975 0.975 0 0.973805 0.974599 0.974595 0.97459 0.974586 0 0 0 0 0 0

A z | +------->

r

Questions: 1)what would possibly cause this kind of results? 2)in discretizing the transformed NS(non-orthogonal boundary fitted coordinate, the velocities are not transformed into this coordinate), i just use taylor series approximation for all the derivatives(normal finite difference method), and i did not adopt a staggered grid system, can this be the problem? please advise. thanks.