After 2 weeks I found the answer for this.
VGs over the nose of 737NGs are to reduce the cockpit noise. These VGs are totally different to the VGs you find near control surfaces.
these cockpit noise reduction VGs are blunt bodies. they blick the airflow so it reduces the local velocity near the windshield, hense the airflow hit the no.1 windshileds is slowed.
it is obvious that these 10 VGs produce some sort of drag but I guess it is neglegible.
Anyhow I havent come across anyother aircraft fixed with these kind of VGs for voice.
cheers!
code0