Minger,
That is interesting. First of all, I am an Electrical Engineer, so I might be wrong in any of my statements.
I thought that FEA analysis takes into account every detail in my structure (two of the differences I had already mentioned) and hence should be accurate. Though I know...
I am trying to compare the fluid velocity given by the closed form solution and FEA analysis for fluid flowing through a channel that is 800u long and 100u wide.
I am using the equation vmax= (gradP)*(radius)^2/(4*viscosity)
I got 8.4cm/s in the former compared to ~10cm/s in the latter...