Flip Fluid - Add velocity to a river loop

[apileofmud]

Hi everyone, Houdini newbie here! 

I'm trying to do a water/river sim where the water goes around the loop as shown below:

Right now the particles are simulated with a flip object with velocity on z set to 0.5. How should I set up the velocity so the particles go around the loop? Or should I use an object to emit particles instead? Not sure what's the best way to approach.

I'd really appreciate your help here!

[pacificpatterns]

I’m not an expert, as I’m still learning flip fluids myself but I think I might be able to point you in the right direction.

Turn on a boundary layer in the flip solver. The boundary layer asks for geometry sop path and a volume velocity path. You can make custom geo or Boolean out pieces of your fluid source geometry. Animating it allows you to compute velocit. a mountain with $F in offset or time could work. Anything to make the geo move. Then you can compute velocity from the deforming geometry and store it into a volume. I’m not clear on how to get velocity values stored on the volume.

The simulation will sample this incoming velocity every frame. So you can influence the sim depending on where you place your geo and how you set up your velocity, Again those are both being read from the boundary layer. I recently learned about this and I’m just doing my best to explain, if anyone has a better explanation I look forward to learning more about this myself. I hope it helps!