I don't know.
It depends on what bike and what screen ( and rider ideally) and what the gap is like

If it is just a bad fit or the screen has been nicked from something else, try it and see. Generally sharp edges and small gaps are bad.

If there is a gap designed into a production vehicle it is probably there for a reason. It could be turbulence but there is also pressure and stability to worry about. Having said that, generally only very expensive scooters ever see the inside of a wind tunnel.

If you tape some wool in front of the gap it will tell you if the air is actually going into or over it, put another so it pokes in the gap and it will tell you where that air is going at different speeds/conditions (don't laugh, that is how we did it before computers)

If the screen is raised off the body quite a bit making a slot that goes on for a few inches they are probably trying to get the air to follow a certain path

Sometimes steering the turbulence away from your head and shoulders is enough to make all the difference to your comfort. The screen might be dumping its flow in your face (turbulent flow rather than actual turbulence) - wooly helmet?


Irev's trick with the straws is a good one.

Sorry, theories are easy, applying them to an unknown shape is tricky

thanks, it was a thought, on the nexus the gap is built in there with any screen , the stock one i have changed for a taller one, and slight turbulence i get now to me fosh which i didnt get with the stock screen, if i ride with visor half down i dont get it, yet makes more vortexes with visor fully down, will try the three screen height adjustments and the 14 rear ride height adjustments at the rear and see how it goes, i will try my other helmet as well, the above was up to 50mph so will have to try on dual carriageway for set up on ride outs cheers

Ill see if i can find one and have a look

Vortices are different to turbulence, but either can cause problems

Turbulence is a chaotic mess, turbulent is a bit messy but going the right way.

Vortices are spirals of air.
The best known ones are where the air spills around the tip of a wing.
You can actually use them to work for you but that is a long story.

its probably a bit of Turbulence then