Different results with interFoam for serial and parallel simulations with fixed time step
Summary
The parallel execution of a two-phase-simulation with interFoam results in a partly very different solution for the flow fields compared to a serial and to other distributed simulations. The simulation consists of a domain initially filled with air. Over time the domain is filled by a water jet from the top. The air leaves the domain at an outlet located on the side. The following figure gives an overview.
The differences are observed for both, metis and simple, decomposition methods. Furthermore, there are also different results with different number of processors (e.g. between 4 and 8).
We have also uploaded the complete case to github.
Steps to reproduce
Clone this github and run simulation on different number of processes
Example case
See here
What is the current bug behaviour?
Results are not equal for different decompositions and also not equal to the serial case. The following figure gives the result of a simulation on 4 (top left) and 8 (top right) processes. Bottom pictures give the result, again 4 (bottom left) and 8 (bottom right) processes, with a limited Courant number.
The above figures show field U on a plane located in the center in z direction of the case. Next figure shows the location of the plane.
What is the expected correct behavior?
The results of different decomposed simulations and the serial simulation should be identical.
Relevant logs and/or images
Environment information
- OpenFOAM version :
OpenFOAM-v211214aeaf8d - Operating system :
openSUSE Leap 15.3 - Hardware info : -
- Compiler :
gcc (SUSE Linux) 7.5.0
Possible fixes
The limitation (see this diff) of the Courant number to a value of 1 gives much more similar results. Comare again bottom pictures within figure above.