Re: [Nektar-users] what is the boundary condition for the first and second intermediate velocity field?
Hi Ding, I don't believe there are any boundary conditions explicitly applied to \hat{v}. Indeed I think if you were to do this I suspect you would end up with the wrong pressure; the combination of the convective term without any BCs applied to them, together with the pressure boundary condition is then consistent with the original equations meaning that the Helmholtz solve for velocity (where the velocity BCs are imposed) will impose the divergence condition. Or at least I believe is the case. Others may have an alternative opinion. Cheers, Dave On Fri, 2016-08-19 at 22:53 +0800, 丁老师 wrote:
Thank you very much. I know the paper of the karniadakis. what i mean is the value of the first intermediate velocity " v caret" on the boundary, since we need to compute the "nabla dot v caret " for the source term of the pressure equation. Regards
At 2016-08-19 21:27:05, "David Moxey" <d.moxey@imperial.ac.uk> wrote:
Hi Ding,
Sorry, a bit confused by the question. Do you mean in the velocity correction scheme? If so, we use a so-called high-order pressure boundary condition for the Poisson solve (this is documented in the book by Karniadakis and Sherwin and is in a paper somewhere), and the velocity conditions are imposed at the last Helmholtz solve step.
Cheers,
Dave
On 18 Aug 2016, at 10:40, 丁老师 <ztdepyahoo@163.com> wrote: Dear Nektar group: Could you please give me some suggestions about the boundary condition for the first and second intermediate velocity field? Does it use the same with the real velocity boundary conditions. Regards Your Sincerely Ding _______________________________________________ Nektar-users mailing list Nektar-users@imperial.ac.uk https://mailman.ic.ac.uk/mailman/listinfo/nektar-users
-- David Moxey (Research and Teaching Fellow) d.moxey@imperial.ac.uk | www.imperial.ac.uk/people/d.moxey
Room 364, Department of Aeronautics, Imperial College London, London, SW7 2AZ, UK.
-- David Moxey (Research and Teaching Fellow) d.moxey@imperial.ac.uk | www.imperial.ac.uk/people/d.moxey
Room 364, Department of Aeronautics, Imperial College London, London, SW7 2AZ, UK.
Hi Dave, Ding, I agree this is the case. We do not typically impose any boundary conditions on the intermediate field. If you consider a version of the scheme where it is applied in a semi-Lagrangian setup then a boundary condition is adopted but not for the standard scheme. Cheers, Spencer. On 19 Aug 2016, at 17:11, David Moxey <d.moxey@imperial.ac.uk<mailto:d.moxey@imperial.ac.uk>> wrote: Hi Ding, I don't believe there are any boundary conditions explicitly applied to \hat{v}. Indeed I think if you were to do this I suspect you would end up with the wrong pressure; the combination of the convective term without any BCs applied to them, together with the pressure boundary condition is then consistent with the original equations meaning that the Helmholtz solve for velocity (where the velocity BCs are imposed) will impose the divergence condition. Or at least I believe is the case. Others may have an alternative opinion. Cheers, Dave On Fri, 2016-08-19 at 22:53 +0800, 丁老师 wrote: Thank you very much. I know the paper of the karniadakis. what i mean is the value of the first intermediate velocity " v caret" on the boundary, since we need to compute the "nabla dot v caret " for the source term of the pressure equation. Regards At 2016-08-19 21:27:05, "David Moxey" <d.moxey@imperial.ac.uk<mailto:d.moxey@imperial.ac.uk>> wrote: Hi Ding, Sorry, a bit confused by the question. Do you mean in the velocity correction scheme? If so, we use a so-called high-order pressure boundary condition for the Poisson solve (this is documented in the book by Karniadakis and Sherwin and is in a paper somewhere), and the velocity conditions are imposed at the last Helmholtz solve step. Cheers, Dave On 18 Aug 2016, at 10:40, 丁老师 <ztdepyahoo@163.com<mailto:ztdepyahoo@163.com>> wrote: Dear Nektar group: Could you please give me some suggestions about the boundary condition for the first and second intermediate velocity field? Does it use the same with the real velocity boundary conditions. Regards Your Sincerely Ding _______________________________________________ Nektar-users mailing list Nektar-users@imperial.ac.uk<mailto:Nektar-users@imperial.ac.uk> https://mailman.ic.ac.uk/mailman/listinfo/nektar-users -- David Moxey (Research and Teaching Fellow) d.moxey@imperial.ac.uk<mailto:d.moxey@imperial.ac.uk> | www.imperial.ac.uk/people/d.moxey<http://www.imperial.ac.uk/people/d.moxey> Room 364, Department of Aeronautics, Imperial College London, London, SW7 2AZ, UK. -- David Moxey (Research and Teaching Fellow) d.moxey@imperial.ac.uk<mailto:d.moxey@imperial.ac.uk> | www.imperial.ac.uk/people/d.moxey<http://www.imperial.ac.uk/people/d.moxey> Room 364, Department of Aeronautics, Imperial College London, London, SW7 2AZ, UK. _______________________________________________ Nektar-users mailing list Nektar-users@imperial.ac.uk<mailto:Nektar-users@imperial.ac.uk> https://mailman.ic.ac.uk/mailman/listinfo/nektar-users Spencer Sherwin McLaren Racing/Royal Academy of Engineering Research Chair, Professor of Computational Fluid Mechanics, Department of Aeronautics, Imperial College London South Kensington Campus London SW7 2AZ s.sherwin@imperial.ac.uk<mailto:s.sherwin@imperial.ac.uk> +44 (0) 20 759 45052
participants (2)
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David Moxey
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Sherwin, Spencer J