Numerical oscillations in test case `Left_coronary_inlet_pressure_wave_outlet_coronary.in` when using smaller time step

[Fra-Sala]

Description

Description
When running the test case Left_coronary_inlet_pressure_wave_outlet_coronary.in, I observed numerical oscillations in the flow rate when using a smaller time step than the value used in the parameter file.

With dt = 1e-3, the flow rate exhibits noticeable numerical oscillations (visible in Paraview). Oscillations remain even if I postprocess myself the sim data, so Paraview is not the culprit.
With the default dt = 5e-3, no oscillations appear.

Questions

• Is this behaviour intended or expected for this test case?
• If it is expected, could you explain briefly why reducing dt may produce oscillations in this setup?

Reproduction

In particular, I:

1. Used the provided test case Left_coronary_inlet_pressure_wave_outlet_coronary.in.
2. Set the time step to dt = 1e-3 (the default was 5e-3).
3. Ran the simulation and evaluated the flow rate at a section of the LAD (see attached png).

Environment

• OS: Ubuntu 22.04
• Skyline solver
• commit: 66b31b4

Expected behavior

Using a smaller time step would normally improve stability or accuracy, so oscillations were not expected.

Additional context

No response

Code of Conduct

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