Fluid not flowing straight

Question

I am trying to simulate fluid flowing in the top and out the bottom of a tank through pipes. A little like in this picture:

At the moment, the top inflow seems obstructed for the first few frames and then flows in an unrealistic, obstructed way. Please see the gif:

If you look at the top pipe, it is not flowing smoothly. I've tried rotating the inflow object in the top pipe (90 degrees), checking the surface normals are all pointed outwards and giving the inflow a slight positive Z initial velocity and none of these seemed to make a difference.

It might be worth noting that when I run the animation without baking the mesh I see just a small amount of fluid flow along the bottom of that top pipe.

I am new to this so forgive my ignorance!

I think I read somewhere in the manual that if you have multiple fluids in your scene you're supposed to design them separately and then combine them later? But I didn't understand it really and now I can't find that part of the manual!

Answer 1

It looks as though the resolution of your fluid simulation is too coarse. Generally, the fluid can only interact properly with the obstacles if the resolution is fine enough that the significant details of the obstacles can be detected. The "Resolution Divisions" parameter in the domain settings gives you control over this.

The challenge is to make the number of divisions high enough that all obstacles and boundaries are correctly recognized but small enough to keep baking times and memory manageable...

The "multiple fluids"-issue you mention is only a problem if you need different fluids with different properties (e.g. honey and oil) in the same scene. As they can not really interact with each other this way, that's a somewhat advanced topic requiring quite a bit of trickery.

Fortunately, different bodies of the same fluid (as in your case) are not a problem for the simulation.