Question for Stafford1500

What does vortex generators do to the air stream after it leaves the surface? 

Will VG's provide a reduction in the amplitude of the turbulence of the air coming off the end of a surface?

Monday bump.

Just got back to using a computer after a few days offline...

VG's basically spin the high energy air from off the surface into the low energy air near the surface. This is used to keep the flow from seperating in most cases. The off surface result is a small twisting/rotating (thus vortex) structure in the air. Since the local air speed is still moving front to back at the same speed, and the air is spining, the local airspeed is higher, giving a lower local pressure (Bernoulli - high speed = low pressure). The problem is that adding that energy requires that the energy come from somewhere. In this case the extra energy comes from the engine making up for the increase in drag from the vortex creation. Sometimes the vortex flowing off the body can be used downstream to change the flow around other components (like wings). If you get the rotation direction and energies just right you can use a vortex to act as seal to blow flow entering an area OR to help get the flow to turn more aggressively into an area that would normally be stalled.

In reply to stafford1500 :

Thank you.

I think it's worth experimenting with for my situation.

Thanks for that explanation of vortex generators. I forgot that even if the air is spinning, it still has to go a fast as the air around it thanks to Bernoulli. 

Thank you, Steve.

You can watch (or re-watch) his appearance on GRM Live right here:

I guess I should explain a little about what I'm trying to do Incase Steve or anyone has some suggestions. 

The stock windscreen in my bike is terrible. After a lot of testing and tuning I've made some major improvements. However I just switched back to no screen and it's evident that there's still room for improvement. 

I've reduced the buffeting from a pneumatic Jack hammer to an air chisel through position and angle changes. I'd like to reduce it even farther. I've found that small changes can make a huge difference so some experimenting with VG's may give me what I'm looking for.

In reply to Nick Comstock :

I happen to have a friend that got his masters degree doing research on exactly that sort of thing. He was able to generate anywhere from 20 pounds of lift to 30 pounds of downforce just on the helmet of the driver in an open wheel car. Making the windscreen do the work will be much better than making the helmet do all the work, since the helmet position is VERY sensitive.

The buffeting is also a side effect of the side to side movement of the wake off the windscreen/helmet system. Think sideways as well, not just front to back when dealing with aero issues.