Dear Yiran, Sorry I have been ratter behind on my emails and so am only finally getting to the bottom of them. I am forwarding your message to the user list to see if anyone else has experienced similar issues. One point I would make however is that the SFD methods is good for unsteady flows (like vortex shedding) but cannot find the steady state of a problem that has a real leading eigenvalue such as a hopf bifurcation. The reason is that the flow needs to contain some instance of the steady state. Your problem of a separation bubble might be more similar to the second type of problem and this could be the cause behind the issue. Have you had a chance to look at the paper by Bastien Jordi? Jordi BE, Cotter CJ, Sherwin SJ, 2014, Encapsulated formulation of the selective frequency damping method<http://dx.doi.org/10.1063/1.4867482>, Physics of Fluids, Vol: 26, ISSN: 1089-7666 Where we try to motivate this issue. Cheers, Spencer On 1 Feb 2018, at 03:47, 李依然 <by1504151@buaa.edu.cn<mailto:by1504151@buaa.edu.cn>> wrote: Dear Professor Sherwin, My name is Yiran Li, and I am currently a PhD student at Beihang University in the School of Energy and Power Engineering. I am sincerely sorry for bothering you again but I want to follow up with you to be sure you received my email that I sent on 11th January, 2018 with the title being "Some problems when using SFD method in nektar++ 4.4.1 ( non-convergence)". Recently, I have been trying to use the Selective Frequency Damping (SFD) method implemented in Nektar++4.4.1 to obtain the base flow of an experiment-specified separation bubble, but after weeks of numerical tests, my calculations still cannot converge. I do not know if there is something wrong with my case settings or the case I try to figure out here might fundamentally beyond the scope of the SFD method. For details, a review of my works and results over the past few weeks together with some personal thinking and confusions was attached at that email as the PDF file called “Review on results and some confusions using SFD method” for your reference. Besides, the related session files and field files for some typical cases mentioned in that review were also attached there in the package called “cases”. Now, in case the attachments at that email have been out of date, I have attached them again in this email for your reference. Thank you very much for your patience and look forward to your kindly reply! Best Regards, Yiran Li -----原始邮件----- 发件人:"李依然" <by1504151@buaa.edu.cn<mailto:by1504151@buaa.edu.cn>> 发送时间:2018-01-11 12:24:08 (星期四) 收件人: s.sherwin@imperial.ac.uk<mailto:s.sherwin@imperial.ac.uk> 抄送: b.jordi11@imperial.ac.uk<mailto:b.jordi11@imperial.ac.uk> 主题: Some problems when using SFD method in nektar++ 4.4.1 ( non-convergence) Dear Professor Sherwin and Dr. Jordi, My name is Yiran Li, and I am currently a PhD student at Beihang University in the School of Energy and Power Engineering. Recently, I have been trying to use the Selective Frequency Damping (SFD) method implemented in Nektar++4.4.1 to obtain the base flow of an experiment-specified separation bubble which undergoes a laminar separation while a turbulent reattachment under adverse pressure gradient on a flat plate. However, after weeks of numerical experiments, the calculations still cannot converge. I was wondering if there is something wrong with my comprehension and settings or the case here might fundamentally beyond the scope of the SFD method. For details, a review of my works and results over the past few weeks together with some personal thinking and confusions is attached as the PDF file called “Review on results and some confusions using SFD method” for your reference. Besides, the related session files and field files for some typical cases mentioned in that review are also attached in the package called “cases”. Thank you very much for your patience and any response will be appreciated! Best Regards, Yiran Li ________________________________ 从buaa.edu.cn<http://buaa.edu.cn>发来的超大附件 cases.zip<https://mail.buaa.edu.cn/coremail/viewDownloadFile.jsp?key=1U31SsvkjqIgh48Cr17GF40U3BIq3cKvaexL3Zt1Sn2LjkjCTyCgh48Cr17GF48dantE3BIq3cKvaexL3Ztdan7ErcGpS4APTuxEr18JF1UJwZEXaWCW3ZqpTZJMfeYpz48mjeIk-s71UUUUUD2l39EtjqanVW8AF18KrWUtF4kXrW7yVZYKr4xJUZCmaUtsU18USUjgUnkU77j2U8xU7JjjU03UcJjkU1DUaUj7UexU37j2U88U77jWUeUj-7zD5ipq&code=r7zekpfa> (66MB, 2018年01月18日 12:04 到期) 查看下载信息<https://mail.buaa.edu.cn/coremail/viewDownloadFile.jsp?key=1U31SsvkjqIgh48Cr17GF40U3BIq3cKvaexL3Zt1Sn2LjkjCTyCgh48Cr17GF48dantE3BIq3cKvaexL3Ztdan7ErcGpS4APTuxEr18JF1UJwZEXaWCW3ZqpTZJMfeYpz48mjeIk-s71UUUUUD2l39EtjqanVW8AF18KrWUtF4kXrW7yVZYKr4xJUZCmaUtsU18USUjgUnkU77j2U8xU7JjjU03UcJjkU1DUaUj7UexU37j2U88U77jWUeUj-7zD5ipq&code=r7zekpfa> ________________________________ 从buaa.edu.cn<http://buaa.edu.cn>发来的超大附件 cases.zip<https://mail.buaa.edu.cn/coremail/viewDownloadFile.jsp?key=1U31SsvkjqIgh48Cr17GF40U3BIq3cKvaexL3Zt1Sn2LjkjCTyCgh48Cr17GF48dantE3BIq3cKvaexL3Ztdan7ErcGpS4APTuxEr18JF1UJwZEXaWCW3ZqpTZJMfeYpz48mjeIk-s71UUUUUD2l39EtjqanVW8AF18KrWUtF4kXrW7yVZYKr4xJUZCmaUtsU18USUjgUnkU77j2U88U2UjjU83UcJjkU1DUaUjdUn_UsUj2U88U77jLU08j-7zHH3zl&code=10zmf22z> (66MB, 2018年02月08日 10:48 到期) 查看下载信息<https://mail.buaa.edu.cn/coremail/viewDownloadFile.jsp?key=1U31SsvkjqIgh48Cr17GF40U3BIq3cKvaexL3Zt1Sn2LjkjCTyCgh48Cr17GF48dantE3BIq3cKvaexL3Ztdan7ErcGpS4APTuxEr18JF1UJwZEXaWCW3ZqpTZJMfeYpz48mjeIk-s71UUUUUD2l39EtjqanVW8AF18KrWUtF4kXrW7yVZYKr4xJUZCmaUtsU18USUjgUnkU77j2U88U2UjjU83UcJjkU1DUaUjdUn_UsUj2U88U77jLU08j-7zHH3zl&code=10zmf22z> <Review on results and some confusions using SFD method .pdf> Spencer Sherwin FREng, FRAeS Head, Aerodynamics, Professor of Computational Fluid Mechanics, Department of Aeronautics, Imperial College London South Kensington Campus, London, SW7 2AZ, UK s.sherwin@imperial.ac.uk<mailto:s.sherwin@imperial.ac.uk> +44 (0)20 7594 5052 http://www.imperial.ac.uk/people/s.sherwin/