Two identical fans, one is unducted and other is ducted,both operate at same RPM.
•Does ducted fan require more engine torque than unducted-fan ,measured both at same fan RPM?
power=torque x RPM so in my case more torque mean same as more power("induced power")...
(Engine torque is direct indicator which fan has higher drag at blades.We can make analogy with wall to wall airfoil(represent ducted fan) vs 3D wing (no side walls at wingtips )represent unducted fan.
Here is problem:
I think ducted fan requier more torque for same RPM(maybe I am wrong?),which means it has higher drag than unducted fan,but in theory wall to wall airfoil must has lower drag than 3D wing at same speed and same AoA.
•How explain this contradiction?