How come the velocity of the wind speed in a wind tunnel drops

*on a simple aerofoil

File: airfoil.png (34KB, 830x258px) Image search: [Google]

34KB, 830x258px

Are you talking about the actual inlet flow from the fans, or are you looking at airflow after it's passed the model?

If you're measuring outflow, then yes increased flow separation with angle of attack would probably have some effects on your airspeed.

The wind tunnel I've worked with tares out wall effects. If this is data you've pulled from somewhere like NASA or a decent tunnel, then wall effects probably aren't the cause. If you're working with babbys first wind tunnel, then yeah maybe. Either way you're not giving a lot of details here.

>>8541549
the increase in AoA blocks the air flow, making it harder to travel inside the wind tunnel
then, you need more force to make the air travel at the same speed.

talking about momentum, more energy from the air flow is transferred to the aerofoil with higher AoA, then less energy for the air

This is a small wind tunnel with a 30cm wide test section. The wind speed was measured with a pitot tube mounted behind the aerofoil. I'm leaning towards the fact that the pitot tube was probably just sat in a turbulent area?

>>8541605
That and for a such a small test section, I'd bet the airfoil tends to block airflow as well.