Hi Matt, What are your boundary conditions? I presume it is a zero gradient outlet condition. Are you using the higher-order outflow boundary condition, namely <REGION REF="1"> <!-- outlet !--> <N VAR="u" USERDEFINEDTYPE="HOutflow" VALUE="0" /> <N VAR="v" USERDEFINEDTYPE="HOutflow" VALUE="0" /> <D VAR="p" USERDEFINEDTYPE="HOutflow" VALUE="0" /> </REGION> This should prevent reflections from the boundary into the flow domain. Cheers, Ilteber -- İlteber R. Özdemir On Tue, 5 Sept 2023 at 13:01, Matt Duran <matt.duran60@gmail.com> wrote:
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Dear Nektar++ users,
I have been experiencing issues related to flow in the outlet region of my simulations. I have been running flow past a cylinder at Reynolds number Re = 3900, on some occasions when the vortexes being shed reach the outlet, they cause my simulation to crash. This problem persists for 2D and 3D simulations.
I have tried several fixes such as a finer time step of 5E-5 and making the mesh very high resolution. I have also tried increasing the distance from the cylinder to the outlet, with the outlet being located 40 cylinder diameters downstream from the cylinder. And I have also tried using a higher resolution 'buffer zone' near the outlet and also making the mesh unstructured near the outlet but I still experience crashing.
The issue seems to be that the vortexes get stuck in the outlet boundary and then begin sending pressure and velocity backwards upstream into the flow causing the simulation to crash.
I would greatly appreciate it if anyone had a potential solution or work around to this. I can provide my simulation files if it would help.
Thanks,
Matt Duran _______________________________________________ Nektar-users mailing list Nektar-users@imperial.ac.uk https://mailman.ic.ac.uk/mailman/listinfo/nektar-users