Hi all.. I'm doing this channel flow with square cylinder in the center of channel, and the streamfunction of the bottom wall is zero, the top is 11. So logically speaking, my centered cylinder should have a stream function of 5.5, with fluctuating values at unsteady situation also about 5.5. But no matter how I try with my programme (I'm using finite difference method), I always get a value of some value higher,like 5.7 to 5.8, for my cylinder. Can anyone advise me on what might actually be wrong? I'm using the line integral of the Navier Stokes eqn for cylinder streamfunction determination. Thanks!

(1). When you do line integration, you will have errors from the velocity components and the integration algorithm used. (2). So, you will have to refine you mesh to get more accurate velocity distributions. (3). The other way to do is to solve the stream function equation for the 2-D problem, using the existing velocity field or vorticity field.