Have a look here

http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.23.406&rep=rep1&type=pdf

http://www.sciencedirect.com/science/article/pii/S0021999183712106

Thank you Filippo.

Hi there,

with Fluent you do not have a lot of options. In case of planar channel flow you should apply a periodic mass-flow condition to both inflow and outflow planes. Prior to start the simulation you must apply a perturbed velocity field, for turbulent structures to develop inside the channel.

For flat plate boundary-layer simulation you may want to use synthetic turbulence generator which is available in Fluent as Vortex Method. Though I did not find it useful as synthetic eddies were damped downstream the inlet and I obtained a laminar solution at the end! However, you may write your own code to apply more advanced methods e.g. Lund Recycling method or precursor simulation through using User-Defined Function (UDF).

Regards,

Ehsan

In general for channel flow, you would need to select periodic boundary conditions in the inline direction from inflow to outflow.

For a flat plate, a no slip boundary condition should be selected on the wall (plate surface).

These suggestions are based on theoretical knowledge of the flow so there may be more specific options in Fluent that match your case. 

Thank you Olayoe. Papers suggested by Filippo is a very good read in this regard.