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gdtk-uq / gdtk

The Gas Dynamics Toolkit (GDTk) is a set of software tools for simulating high speed fluid flow, maintained at The University of Queensland and the University of Southern Queensland, Australia.
https://gdtk.uqcloud.net/
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Megathread: Ghost cell free wall boundary issues #4

Open uqngibbo opened 2 years ago

uqngibbo commented 2 years ago

Import of issue #9 from the old repository, originally reported by me.

Nick Gibbons created an issue 2021-12-03

Commit b802b668 swapped to the experimental “type 1” versions of the wall boundary conditions: WallBC_WithSlip, WallBC_NoSlipFixedT, and WallBC_NoSlip_Adiabatic, which do not use ghost cells to implement wall behaviour. This thread is for collecting specific simulations where the ghost-cell free treatment seems to cause problems.

uqngibbo commented 2 years ago

Fabian Zander reports timestep degradation on the flying cube simulation collected in the examples:

The '1' BC actually causes the simulation to essentially stop. It doesn't actually fail, but the time step starts approaching 0 after quite some time in the simulation at which point I've been manually halting the simulation. This doesn't happen at all with the '0' BC simulation.

Step= 150000 t= 1.590e-02 dt= 1.930e-22 cfl=0.40 WC=51835.3 WCtFT=61042856941512818688.0 WCtMS=10315224.9

uqngibbo commented 2 years ago

This issue affects my 11 species 2T blunt body calculations. Failure can be reproduced using the 1cm blunt cone “uniform/one” simulation, with conditions v=6km/s and h=35km. Failure occurs at a CFL of 50, timestep 820, due to invalidate density errors thrown during the preconditioner evaluation in the NK solver. Tested in commit 948bac25 (Note that commit 85efde74 fixes the problem)