Problem with fluid simulation, cannot get fluid to move up a thin pipe

Question

Hi all

So I created a little pipe system which I require water to flow through. It's meant to start by the water getting sucked up through the thin pipe currently located in the water and then flow through the rest of the system. I have tried to create a fluid-inflow object within the bottom end of this pipe (currently covered by water) and set its z inflow velocity up, unfortunately, this is not working. Water starts appearing in random areas outside of the pipe. I think it could be due to the domain being really large compared to the small inflow object, but not sure how to solve the problem. You can also view my blender file at

Any help would be greatly appreciated!

Answer 1

There are several options which make fluid simulator fail while finding correct paths for fluid in this case.

1. Most objects in this scene have scale / rotation unapplied, so just select them all and use options from Ctrl+A menu. In case of fluid simulation, Fluid Sim modifier will not know that the scale of the object was changed if it wasn't applied to the object data. This may lead to unexpected results (same for rotation).
   For more info on why is it important to apply them, see Why is it important to apply transformation to an objects data?.

2. There is internal face inside of your pipe mesh (assumed to water the big vessel with fluid). The face will effectively prevent fluid from going through the mesh, so delete it.

   

   There are also several double vertices in the mesh, remove them with W > Remove Doubles.

3. The pipe, assumed to water the top vessel, consists of several objects; the main pipe has holes where they should connect. This will prevent fluid from coming all the way up to the top vessel because of that hole just in the middle of the main pipe:

   
   _{Smaller part of the pipe was hidden}

   To achieve expected results of animation, join these meshes and make them manifold in the place of joint:

   

   Topology is horrible, however at least they are joined and closed. This can be easily done by closing the gap in the main pipe, and using Boolean Union option to join objects effectively.

   The joint between this joined small pipe and big vessel can be left as is - it will only depend on the resolution of the fluid.

4. The final result will really depend on the bake resolution. If quite low values are used (as 80 or 100), then make sure to scale the pipe a bit up, because otherwise baked fluid will be too fat to flow into it and will just splash in the bottom vessel. You can scale the pipe along normals for that. Fluid baked on higher values should deal with that (although I don't know how much those values should be as I didn't tested it).

Answer 2

I would probably place the inflow object inside the pipe, and then cap the bottom of the pipe so it can't flow out the bottom. Then I would fake the draining of the large water object by keyframing it instead of by simulation.

Should be faster to work with as well. Unless you need really accurate water detail on the large water object, this should work fine. You may want to add some rippled animated displacement to the top to help sell it.