[BECK DING]

I'm trying to run a simulation of steady, laminar flow of water which comes into a rectangular microchannel inlet (1.8mm width and 0.4mm height ),via eleven smaller rectangular channels (0.2mm width and 0.4mm height) and exist via a rectangular outlet (1.8mm width and 0.4mm height ).
For this purpose I have created a 3 dimensional mesh in Ansys Meshing and solved it in FLUENT 15. When it iterates for lower velocities such as less than 1.0 m/s ,the solution converges but it does not converge for higher velocities just like 2.0 m/s.

When I try to switch the inlet to “pressure inlet”, and pressure drop between inlet and outlet is 50 kPa. The average fluid velocity in #5 channel is equal to 5m/s. The Reynolds number base on the average velocity and channel is 1333 so it’s reasonable for me to use laminar model. But I was using fully turbulent models such as k-e models the convergence is good except for the laminar model

Somebody give me some advice please, I'm really not sure what to do next.