It can avoid moving of stilling particles.And it does not affect the direction.
Add a vx limit for the tools.
Multiply and divide vx/vy.
Oh, he means something like WIND?
Yes, but it affects only speed and affects only to particles.
BUMPY
I actually have these...if you want them. (I'll update my mod)
add a DRAG tool is enough
I have VX+ VX- VY+ VY- All seperate tools. So you can make more vector velocities. To change velocity faster hold "shift".