OK, as I see it your TEST will be influenced by a couple of factors.

1. Do you plan to have a cone on the inlet to the fan, you have not indicated direction of air flow so at this stage I have assumed that the air enters the system in the duct attached to the fan.

2 have you designed the radius of the bend as this will have significant effect on the way the air flow behaves in the duct, let me know what the bend design is, or I will recommend a design.

Get back asap it's Sunday evening at 18:57 here, time for a beer or three.