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

737 nose, showing vortex generators under the middle of the cockpit windows

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Apparently, they are there to reduce the cockpit noise. From b737.org.uk:

Notice the 10 small vortex generators above the radome. These reduce the cockpit noise from the windshield by 3dB.

According to this document, the VGs, along with other improvements like damping/insulation changes, window frame improvement and ECS improvements contribute to a total noise reduction of 3 dB (at 35k ft and Mach 0.78). Though their exact impact is unknown, the reason for VGs are there is to reduce cockpit noise.

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  • $\begingroup$ Ok thank you. But which way do they reduce noise? $\endgroup$ – ECJCZ Nov 3 '16 at 13:04
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    $\begingroup$ @ECJCZ 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. $\endgroup$ – aeroalias Nov 3 '16 at 13:25
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    $\begingroup$ @ECJCZ See this paper. It's from guys in Boeing and I wouldn't be surprised if this modification was related to the paper. $\endgroup$ – aeroalias Nov 3 '16 at 14:44
  • $\begingroup$ aeroalias, so, in short, the angle between the fuselage and windshield creates a separation bubble, that is to say, separation of the boundary layer occurs, producing uncontrolled turbulence which in turn produces noise in the cockpit. So, vortex generators are placed right there to avoid, or at least to delay the airflow separation and therefore noise. Is it correct? $\endgroup$ – ECJCZ Nov 3 '16 at 18:07

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