Functional prints:
I printed some air scoops for my ebike hub motor. When this thing spins up it should push air into the motor to cool it.
Yay 3D printed innovation!
Are the big black wholes also openings? If not,are there any other openings? You need to get the air out somewhere 
there are four 1 1/4" holes
Ah ok, these big black dots that we see on the picture? Well but then, great idea!
But @Sven_Eric_Nielsen , as it has one on top with air coming in, wouldn’t the bottom one be an exhaust, letting the air out? So why not do all 4 the same way? 
Works like a helicopter rotor, as the helicopter is moving forward the one blade going towards the front of the helicopter is moving faster than the one going towards the tail. Speed difference means air flow difference. They compensate for that with pitch angle difference, but this is fixed angle, so I think it does what he is wanting it to do. 
@Mark_Cooper
Not quite sure if you try to kidding me or if it’s a serious question
But in the case of a serious question :
Top and bottom doesn’t matter. Velocity and pressure is the only thing that matters. To generate a flow (velocity) you need a pressure difference between inlet and outlet. If there is no outlet with a lower pressure you won’t see a flow. Instead the pressure will just increase to a certain point and then stop until the rotation speed changes.
Mark is right. The bottom scoop will move backward through the air. See, the wheel is rolling on the pavement. So the stationary point is the lowest point of the tire. Everything else is moving forward through the air though with different linear velocities.
It’s got a high enough RPM that it acts like a scoop.
These are mounted on the spinning portion of the wheel.
Yes, the whole wheel is spinning with the same RPM (angular velocity). Now the question is where you put the momentary pivot and what is the velocity of the air relative to that pivot?
Ah, now I understand what he means. Yes of course I also have to consider the velocity of the bike and not only the rpm of the wheel. But still, what I wrote is correct. You need the pressure difference.
And this way you’ll still loose the air flow from the rotation and only get the air flow from the bike velocity into only 1 scoop (which is oriented towards the driving direction). If you keep at least 1 hole open you’ll get the air flow from all scoops by the rotation AND the bike velocity.
And it’ll be watercooled in case of rain…