I added "lids" to this. Basically to flat sheet metal parts covering the front and back of the part. Now normally, I would set the pressure here, since I was normally testing plenums at different pressures. But sdince I only want to see the actual flow here, I selected "Volume flow rate". I am unsure what to set this at...
You uploaded the assembly file but there are no part files for the assembly to reference, so there's no useful data in your zip archive. Regardless, I did see the saved thumbnail preview, it looked like a thin plate with a honeycomb pattern cut into it.
What you should consider before you simulate this design is how you will be testing your prototypes. Are you planning on putting them into a wind tunnel? That seems like the most logical way to test this part. You should create your simulation similar to your experimental test stand, so you can easily verify your results in the lab and have confidence in simulation of other designs further down the road.
Finally, for a repeating pattern like this I would recommend performing your simulation on just the smallest repeating unit of your pattern. You can use the symmetric boundary conditions in your simulation to force the flow to move through your plate rather than across it.