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Maniphest T72643

[Mantaflow] Incorrect fluid flow direction
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Description

System Information
Operating system: Windows-7-6.1.7601-SP1 64 Bits
Graphics card: AMD Radeon HD 7560D ATI Technologies Inc. 4.5.13399 Core Profile Context 15.200.1062.1004

Blender Version
Broken: version: 2.82 (sub 6), branch: master, commit date: 2019-12-20 00:09, hash: rBc3782ebf44d8
Worked: (optional)

Short description of error
Fluid drops to the side. Fluid must fall strictly down.

Exact steps for others to reproduce the error
Run the simulation in this scene:

test_02.zip82 KBDownload

And the particles will look like this:

Related Objects

Event Timeline

Pavel (Pavel_Blend) created this task.Dec 22 2019, 5:01 PM
Jacques Lucke (JacquesLucke) changed the task status from Needs Triage to Confirmed.Jan 15 2020, 11:28 AM
Jacques Lucke (JacquesLucke) added a project: Physics.
Jacques Lucke (JacquesLucke) added subscribers: Sebastián Barschkis (sebbas), Jacques Lucke (JacquesLucke).

Something looks very wrong here. I could not figure out what is causing this yet. Are you able to reproduce it in a new file? If yes, please provide exact steps to reproduce it.

Bastien Montagne (mont29) changed the task status from Confirmed to Needs Information from User.Jan 15 2020, 3:53 PM
Pavel (Pavel_Blend) added a comment.Jan 15 2020, 5:09 PM

This error occurs in any scene. It is enough to increase the parameters Timestaps Maximum and Minimum. Here is the instruction:

  • Add domain (liquid)
  • Add a source of fluid (Inflow)
  • Set Timesteps Maximum and Minimum to a single value that is higher than the standard value. For example, set the value to 8.
  • Run the simulation.

In fact, this error is visible at low Timesteps, although less noticeable. With a value of 20, the simulation is extremely unstable:

Sebastián Barschkis (sebbas) added a comment.Jan 15 2020, 6:25 PM

I think it all boils down to the Surface Tension value (Domain settings) in the file. Disabling it, i.e. change from 2.0 to 0.0, makes the liquid drop straight down again.

Investigating the influence of that value remains to do.

Richard Antalik (ISS) changed the task status from Needs Information from User to Confirmed.Jan 17 2020, 2:35 PM
Bastien Montagne (mont29) changed the subtype of this task from "Report" to "Bug".Jan 20 2020, 10:46 AM
Sebastián Barschkis (sebbas) closed this task as Resolved.Jan 21 2020, 9:08 PM
Sebastián Barschkis (sebbas) claimed this task.

Closing this report since there is nothing to fix at this point. More information should go into the documentation instead.

Richard Antalik (ISS) mentioned this in T73805: Liquid inflow randomly changes direction.Feb 17 2020, 8:30 AM