So first the “emitter” object seemed to be just a flat geometry and this could make the simulation explode or behave weirdly, so I put a Shell modifier on it.
However, the more serious issue in your case was that the emitters were also very small - just a couple of voxels wide, so this made them emit irregularly. Phoenix turns emitters into voxels internally, so when the emitters are very small compared to the size of a voxel, they could start emitting in the wrong direction (due to skewed normals) or could even get completely ignored by the solver if they are too small. So I added a Push modifier on top of the Shell modifier and used Push Value of 0.01m.
This made the emitters larger and they emit all the time now without glitches during the rotation, but now they started to emit in all directions, so I added a Discharge Modifier to the Source to make them emit only downwards.
I used the Normal in the Z direction for the modifier and told it to emit only when the normal is very close to -1, meaning it points almost straight down:
A final change was that I animated the Emit Liquid checkbox on the Source from OFF at frame 0 to ON at frame 1, because otherwise the liquid changed direction during the first frame as Phoenix needs one frame at the start of the simulation to understand if a geometry is moving or rotating.
An additional note is that since you’ve enabled splash simulation, by default the Splash particles eat away from the liquid and this makes the liquid mesh quite jagged and uneven, so for my screenshot at the top of the post I turned off Splash simulation off.
What I don’t understand is why the first 2 to 3 frames work as expected and the Sim starts doing weird things
I tried to increase the voxel size and I gained 1 frame of correct behavior but obviously the Sim slow down quite a bit, and I use flat emitter on more than 60 Sims and I never encounter a problem in fact I have a similar spinning object maybe not going that fast that it works well.
Ah, sorry but you missed the part where I animated the Emit Liquid checkbox - I explained why this matters.
And about the larger shape and behavior of the liquid - in short, it’s about the size of the emitter. You could increase the size of the emitter or increase the grid resolution, but if you change the resolution, the scene would slow down.
WHY this is the reason and why exactly it almost looks like it’s working - in short - by chance. I am going to have to go into a very long story with a lot of technical details in order to explain it entirely, so in short - if the emitter size or an obstacle size is about 1-2 voxels, then they are too small and the solver could miss it entirely or account of it, but it would create glitches. As the emitter spins, it travels between voxels so sometimes it could intersect 2 voxels, other times 3 voxels, and this changes its behavior - in this specific scene, the normal of the emission changes.
I try increasing the size of the emitter a lot and the result is the same, the strange part is that isn’t irregular is on an exact frame that it starts to simulate wrong.
So I don’t think that the size of the emitter is what’s causing the problem
No, what you did doesn’t solve the problem in fact it gives the wrong result from the start, the image that you shared is not what I want
I already tried what you did and this is not the result that I want, the water should stay in place no movie with the emitter, Like in the first 2-3 frames of the untweaked simulations