Fluid Inflow Fails To Fill Simple Tank Depending On Position In Tank A simple tank (fluid obstacle) is filled by an inflow object.

If the inflow object is positioned inside the tank at about half the tank's depth, it begins filling the tank at a reasonable rate, but then the level stagnates despite the inflow's continuing constant rate.



If all is identical, except that the inflow object is positioned just above the tank. It fills the tank at a reasonable rate and then overflows (reasonably correct behavior).



(I am only allowed two links, so can't post the blend file)

Why does the first case fail to fill the tank? 

Other Info:


Scene is set to Blender units.
The domain dimension are 1.1x, 0.8y, 0.8z
The domain Real World Size is 0.5m (Setting it to 1.1 makes little
difference)
All scales have been applied.
All normals are correct and meshes are manifold.
The inflow Volume Initialization is set to Volume, with an inflow
velocity of z = -0.5
The obstacle Volume Initialization is set to Shell.
Bake resolution is 80 (Running at 200 makes little difference)


I have varied the obstacle impact factor, the domain optimization grid levels and compressibility, simulation speed, and a few other things. The only things that have significant effect are the height of the inflow object, a significant decrease in domain real world size, or a significant increase in inflow velocity.

In the real world, if I remember, the inflow velocity would equate to some sort of velocity head. And I suppose if this is low, the inflow might be cut off due to increasing static head on the inflow object. But I didn't think the fluid simulator took account of these types of things(?). That is, I thought the inflow velocity was supposed to be non-changing.

Thanks for any explanations.

EDIT: Attempting to upload .blend for case where inflow is inside tank.

Blend file for inflow object inside tank (Second upload try)
I had posted this question on blenderartists.org a week or so before posting it here.  I just received a particularly good answer from the fluid sim coders themselves.  You can read their response in the link below.

In summary, this is a known limitation of the fluid simulator.  They discuss the low-level details and propose possible modifications to the simulator code.  In the meantime, fluid inflow objects generally should not be submerged, and (I gather) should also not be at an elevation lower than the final fluid level of something they are intending to fill (even if they are outside the vessel to be filled). Of course, this all depends on the level of accuracy of the simulation you are after.

Here's the link.

https://blenderartists.org/forum/showthread.php?410338-Fluid-Inflow-Fails-To-Fill-Simple-Tank-Depending-On-Position-In-Tank