can i use any other CFD model for micro scale flows or the mesh?
 

Hi,
Actually, I am trying to calculate friction factor for flows in rectangular sinusoidal mini-channel, while the height, width length are .250, 1 and 1 mm respectively, I also tried to model the mesh by following a published research paper, the developed mesh sizes where 1million to 4 million cells.

But still, the results were far away from the theoretical and experimental values. like the expected friction value was expected around 0.2 but the values I got were more than 1.
For the analysis, I considered the viscous laminar model with velocity inlet and press outlet were B. conditions. while the considered Re number is 100,
so am I supposed to use any other CFD model? or the problem is with the mesh?
Thanks in advance

Try adding some prism layers. You probably don't need to worry about stretching but it really helps to have a few layers that are wall parallel because it really helps in computing the gradient near walls. Even as few as 3-5 layers can do wonders.

Did the referenced paper also use a tet mesh? You need a lot more tets than hexahedral cells to make up for the poorer gradients that you get with tets. Your geometry looks simple enough to where a hexahedral or polyhedral mesh could be easily generated. That could help, but try the prism layers first.