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enter image description here

I have a fluid sim under Blender 2.80 which requires liquid to flow into a main structure and fill side channels off (imagine underground passages flooding or a storm drain backing up).

Past a certain relative width, I cannot get the 'liquid' to flow into these smaller side areas, even with a lowered viscosity; all the fluid does is gain height, as the level behind rises, and inch forward rather than flow in. The relative width of the side channels seem to be important as I've sized a test area to 5m x 5m, then magnified it to 50m x 50m and still have the same difficulty (Transforms applied, afterwards).

Having been through boundary type settings, viscosity settings, domain height (less volume is not necessarily better) and one or two other options (3am never is a good time to still be working, let alone remembering) can anybody suggest other parameters which will allow the simulation to unfold as hoped? A much higher resolution? Boundary subdivisions? Animal sacrifice?

I've reproduced the effect in the attached test file.

Thanks, Quin.

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First, in the Domain options Set Boundary to Free Slip. With just this change in the file you attached I got as far as this:

enter image description here

You could probably play with subdivisions / surface smoothing or make the timeline longer. It might also help to make the domain only as high as the obstacle, so the fluid doesn't overflow before filling the smaller channels.

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  • $\begingroup$ That's an improvement; thanks – is that over the 80 second sample runtime? The above demo gif is taken from a sample running four subdivisions: no particular benefit and the loss of several hours processing time and twenty or so gigs of disc cache, with rotten playback, even before render. Domain height on this demo is a thumb-suck only; tests showed that a lower domain 'ceiling' eventually restricted flow rather than allowing a better fill, but I just needed something to show the problem, really. $\endgroup$ – Quin Benson Sep 18 at 10:27
  • $\begingroup$ @QuinBenson oh ok. The screenshot was at the last frame in the timeline from your demo. The only thing I changed was the boundary to free slip, I'm assuming fussing further with the settings should improve it. Check this video about resolution youtube.com/watch?v=CqqWlSNdbxk $\endgroup$ – Luciano Sep 18 at 12:35

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