Hi

I'm starting with dynamics in Houdini and this is the first issue I encounter. Hope you guys can help me out.

I create a tube where an emitter is emitting particles into. It's filling up ok, untill the fluid reaches the height of the emitter….and then it stops filling the tube.

Any ideas? Thanks in advance.

Hi

anyone? The rephrase the question : can you have an emitter inside a fluid without breaking the simulation? Thanks.

First off great job on your racetrack!

Submerged FLIP emitters require you to additional fluid velocity and an additional divergence field source.

Initial FLIP emitter velocity is usually added in SOPs using the Fluid Source SOP's velocity tab. In this example, a simple velocity down in Y is added to help push the fluidin.

Divergence adds pressure in the area you specify. WIth FLIP you have a convenient divergence field in the source fluid density field. To hook this up is straight forward.

Divergence fields are best added manually and wire in to the third Velocity input to the FLIP Solver (RMB on input tabs to see input hints). Any velocity adjustment prior to the pressure solve including divergence goes in to this third velocity input.
Add a Source Volume DOP then channel reference the object target FLIP Source. Same for the Source Volume. Then manually type in “divergence” for the Add To Field.
Finally make sure that the Volume Option for source is set to Copy which means replace this field explicitly on every timestep.


Reason Why:
Witih Flip fluids and standard emitters, the pressure of the emmiter is essentially at the same pressure as the fluid. Once the fluid encases the emitter, the emitter no longer emits fluid as the pressure is equal.

To add pressure and flow, you add divergence and initial velocity. Now you have a source just like a water hose where there is additional pressure and velocity to inject fluid in to the fluid.

Adjust the values to suit.

I also channel referenced the divergence to the fluid source cut in half. The idea is to keyframe the source emission and the divergence will be scaled along with the source emission.

Note that the source velocity is in SOPs so you may want to channel reference this to the FLIP source emission value as well to completely automate things.

Hi

thank you for the compliment.
The divergence was exactly what the simulation needed, thank you!