Which compressor blades run at a higher angle of attack: LP or HP compressor blades? In a jet engine: Do Low pressure compressor blades run at higher angle of attack, or the High pressure compressor blades run at higher angle of attack?

What is the purpose of the vortex generators located right in front of the Boeing 737's windshield?

Basically, the angle between the fuselage and windshield creates a separation bubble, which causes unsteady pressure fluctuations on the window, leading to noise. The addition of the VGs reduces the size of this separation bubble and turbulent boundary layer, thereby reducing noise

Vortex generators are used to create laminar airflow. Could be there for drag issues or possibly to reduce wind noise in the cockpit.

What are the advantages and disadvantages of having landing gear doors? To make comparison easy, let us take the example of B737 and A320, both similar aircrafts with retractable landing gear. As seen on the photo below, the B737 doesn't have gear doors for the wheels,     but the A320 does