adding noise/field effects in certain areas

Lifted from the Houdini help page.. Useful for localised noise/breakup

You can attach DOP nodes that modify velocity fields, such as Gas Turbulence, to the fourth ("Advection") input of the Pyro solver node. Most field-modifying nodes have some way to scale the effect by a mask field.

Create a geometry object in the shape of the area you want to affect.

Convert geometry to a fog volume - use an isooffset

In the DOP network, add a SOP Scalar Field node after the Pyro object.

• Turn on Use SOP Dimensions.
• Set the SOP path to the path of the fog volume object (for example /obj/mask_object). Make sure Use Object Transform is on.
• Set the Data Name to something indicating the purpose of this field, for example NoiseMask.

This attaches the fog volume as field data on the Pyro object with the given name.

Create a Gas Turbulence node and connect it to the fourth ("Advection") input of the Pyro solver.

• On the Bindings tab, set the Density Field to the name of the mask data, for example NoiseMask. The effect of the node is multiplied by the value of this field.
• Use the controls on the Turbulence Settings tab to control the amount of turbulence added.

reliable(r) collision objects in FLIP

The deforming object shelf button serves most collision purposes, even for static objects (turn off use deforming objects) but sometimes it doesn't quite cut it.

Add a trail node, set to "calculate velocity" to your moving geometry.
Create a VDB from polygons node, setting the name of the volume to "collision" and add a point attribute at the bottom, choosing the "v" as the option. Name this "collisionvel". These names are defaults in Houdini.

In your FLIP sim dop-network, add a "volume source". Set the initialisation to "collision" and navigate the SOP path to the VDB you made earlier. Set the scale to -1, because that's how the maths work..and change the velocity to whatever you want..1 is probably sensible.
Finally plug the volume source into the "volume" connection tab of the Flip solver.

That should be it.

velocity volume fields like Maya

It's possible to make a piece of geometry, pump it through a PointVOP and give it some velocity, using constants, curl noise or whatever method you like.
Then convert the polygon to a VDB, using the V point attribute. Name the field "vel".

Within POPs/dynamic network use an advect with volume operator. The defaults should keep the velocity's affect within the volume created.

If this doesn't work as expected you might need to use a Geometry Wrangle (within the POP/Flip/dynamics)
Using the code below, you'll want to set the 2nd input (in the input tabs) to the velocity volume created earlier.

vector vel = volumesamplev(1,0,@P);

v@force += vel * ch("scale");

v@a = vel;

Basically we're affecting the velocity via a force, rather than adding directly to it - to avoid overly strong changes in velocity. We also have extra control with a scale slider & the "a" attribute is a little debug value to watch out for in the Geometry Spreadsheet.
Note - you might have to really crank up the velocity values, depending on the current velocity of the existing particles/fluid/whatever.

*NOTE* The Geometry Wrangle should be plugged into the particles tab of the solver! (2nd one)