Hello everyone,
I am trying to repeat the NACA0021 test of Witherden, Jameson (2020) (https://arc.aiaa.org/doi/abs/10.2514/1.J058434), Sec D. Basically, starting with order = 1 without antialiasing with tend = 100.0 and with Re = 27000 (i.e. mu = 0.000037), I attempted restarting from there with order = 4 activating antialiasing for another 300 t (i.e. tend = 400) and modifying the Re to 270000 (mu = 0.0000037).
The first part of the simulation was completed without errors. However, the restarted simulation crashed after time 107.28, with the following error:
RuntimeError: Minimum sized time step rejected
From the forum, I already noticed that such kind of error can happen when restarting the simulation with a different order (see page https://pyfr.discourse.group/t/naca-0021-airfoil-in-deep-stall-minimum-sized-time-step-rejected/295).
I adopted the p4_aa.ini config file as a template for my simulation, available within the supplemental material of Park, Witherden, and Vincent (2017) (see https://arc.aiaa.org/doi/full/10.2514/1.J055304). The relevant differences between the warmup and restart phase are as follows:
warmup
[constants]
...
mu = 0.000037
...
[solver]
...
order = 1
#anti-alias = flux, surf-flux
...
[solver-time-integrator]
...
tend = 100.0
...
restart
[constants]
...
mu = 0.0000037
...
[solver]
...
order = 4
anti-alias = flux, surf-flux
...
[solver-time-integrator]
...
tend = 400.0
...
I kept the rest of the file unchanged, therefore the filtering section for both config files is:
[soln-filter]
freq = 0
cutoff = 0
order = 16
alpha = 36
Can someone give me some hints on how to heal/monitor the instability that is making the code crashing?
For sake of clarity, I adopted the mesh naca0021_p4_4c.msh for this test, that is available within the supplemental material of the paper Park, Witherden, and Vincent (2017).
Regards,
Federico Cipolletta.