Deformers let you influence particle positions in a variety of ways.
The deformers operate in the same way as they do for geometry. You can also layer deformers.
You can also combine particle deformation with forces: deform the particles, then apply the desired forces to the intermediate object. Alternatively, you could apply forces to particles before the application of a deformer.
For example, particles within a flow deformed with a bend deformer will not slow down or speed up in relation to their position within the bend.