******************* This email originates from outside Imperial. Do not click on links and attachments unless you recognise the sender. If you trust the sender, add them to your safe senders list https://spam.ic.ac.uk/SpamConsole/Senders.aspx to disable email stamping for this address. ******************* Dear all, I am using the robin boundary condition in Nektar+ but have some problems understanding how it works. The b.c. I want to impose is D* gradient {u} + 0.5 * u = 0 in which D is the diffusion constant (same as the D value used in the adjacent element), u is the unknown field. To do this I normalize the b.c. into the form of gradient {u} + 0.5 / D * u = 0, and specify the robin boundary condition as <R VAR="u" PRIMCOEFF="0.5/D" /> This setting does not yield the correct answer, unless the special case that D = 1.0. Could anyone please tell me what is wrong here? Thanks, Tengfei Zhang
HI Tengfei, What you propose should be working but I need to set up a test to double check. Do you have an input file that you have been running? Cheers, Spencer. Spencer Sherwin FREng, FRAeS Head of Aerodynamics Section, Director of Research Computing Service, Professor of Computational Fluid Mechanics, Department of Aeronautics, s.sherwin@imperial.ac.uk<mailto:s.sherwin@imperial.ac.uk> South Kensington Campus, Phone: +44 (0)20 7594 5052 Imperial College London, Fax: +44 (0)20 7594 1974 London, SW7 2AZ, UK http://www.imperial.ac.uk/people/s.sherwin/ On 11 Jul 2020, at 13:16, zhangtengfei@sjtu.edu.cn<mailto:zhangtengfei@sjtu.edu.cn> wrote: This email from zhangtengfei@sjtu.edu.cn<mailto:zhangtengfei@sjtu.edu.cn> originates from outside Imperial. Do not click on links and attachments unless you recognise the sender. If you trust the sender, add them to your safe senders list<https://spam.ic.ac.uk/SpamConsole/Senders.aspx> to disable email stamping for this address. Dear all, I am using the robin boundary condition in Nektar+ but have some problems understanding how it works. The b.c. I want to impose is D* gradient {u} + 0.5 * u = 0 in which D is the diffusion constant (same as the D value used in the adjacent element), u is the unknown field. To do this I normalize the b.c. into the form of gradient {u} + 0.5 / D * u = 0, and specify the robin boundary condition as <R VAR="u" PRIMCOEFF="0.5/D" /> This setting does not yield the correct answer, unless the special case that D = 1.0. Could anyone please tell me what is wrong here? Thanks, Tengfei Zhang </html_______________________________________________ Nektar-users mailing list Nektar-users@imperial.ac.uk<mailto:Nektar-users@imperial.ac.uk> https://mailman.ic.ac.uk/mailman/listinfo/nektar-users
HI Tangfei, In the attached test case which has all boundary conditions I have modified the PRIMCOEFF to a non-unit value and modified the exact value accordingly. It seems to run with a non-unit value. Cheers, Spencer. Spencer Sherwin FREng, FRAeS Head of Aerodynamics Section, Director of Research Computing Service, Professor of Computational Fluid Mechanics, Department of Aeronautics, s.sherwin@imperial.ac.uk<mailto:s.sherwin@imperial.ac.uk> South Kensington Campus, Phone: +44 (0)20 7594 5052 Imperial College London, Fax: +44 (0)20 7594 1974 London, SW7 2AZ, UK http://www.imperial.ac.uk/people/s.sherwin/ On 11 Jul 2020, at 13:16, zhangtengfei@sjtu.edu.cn<mailto:zhangtengfei@sjtu.edu.cn> wrote: This email from zhangtengfei@sjtu.edu.cn<mailto:zhangtengfei@sjtu.edu.cn> originates from outside Imperial. Do not click on links and attachments unless you recognise the sender. If you trust the sender, add them to your safe senders list<https://spam.ic.ac.uk/SpamConsole/Senders.aspx> to disable email stamping for this address. Dear all, I am using the robin boundary condition in Nektar+ but have some problems understanding how it works. The b.c. I want to impose is D* gradient {u} + 0.5 * u = 0 in which D is the diffusion constant (same as the D value used in the adjacent element), u is the unknown field. To do this I normalize the b.c. into the form of gradient {u} + 0.5 / D * u = 0, and specify the robin boundary condition as <R VAR="u" PRIMCOEFF="0.5/D" /> This setting does not yield the correct answer, unless the special case that D = 1.0. Could anyone please tell me what is wrong here? Thanks, Tengfei Zhang </html_______________________________________________ Nektar-users mailing list Nektar-users@imperial.ac.uk<mailto:Nektar-users@imperial.ac.uk> https://mailman.ic.ac.uk/mailman/listinfo/nektar-users
participants (2)
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Sherwin, Spencer J
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zhangtengfei＠sjtu.edu.cn