Wind
Accelerates particles up to a maximum speed.
Once the maximum speed is reached, the particles maintain that speed. It can also be used to add turbulence with no wind direction vector.
Using Wind
Click the
Wind button on the Drive Particles tab.Click
the 
particle system you want to be affected and press Enter to confirm your selection.Specify the node settings in the operation controls toolbar or parameter editor.
For specific parameter help see the Wind node help.