- Nektar-users - imperial.ac.uk

Mesh growth rate control for NekMesh
by Shujie Jiang 27 Mar '21

27 Mar '21

******************* 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 Nektar users, I am using NekMesh to generate mesh for my simulation. I found some reflection on the edge of the coarse mesh and the refine mesh (like the picture below). [cid:3879835e-1dea-4ad8-952e-7a020d496fdd][cid:f2252f49-e539-4496-aafd-4b0319898a27] Can I control the growth rate of mesh to give a smooth transition from a refined mesh to a coarse mesh? Thank you very much! Kind regards, Shujie University of southampton

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A Question Concerning how to Include Source Terms in ShallowWaterSolver
by Boyuan Yu 27 Mar '21

27 Mar '21

******************* 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. ******************* Hello all, I would like to express my appreciation for the efforts made by the developer team and community to create such a great open-sourced software. Currently, I am working with shallow water equations and my application requires the inclusion of the source terms of: (1) bed-friction term; (2) channel slope term. However, these particular source terms are not included in ShallowWaterSolver of Nektar++ yet and it seems to be not possible to use any forcing terms in ShallowWaterSolver. As far as I am concerned, the method to use these source terms is to modify the solver ShallowWaterSolver source code and recompile all the library. But this method is quite time-consuming. So I am writing to ask is there any simpler way to implement this functionality. Thank you in advance for your answer. Boyuan Yu

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Re: [Nektar-users] Residuals Stability Simulation
by Gao, Ankang 15 Mar '21

15 Mar '21

Hi Matt, If you are using the ModifiedArnoldi driver, the Residual after each iteration is shown in the *.evl file, for example, -- Iteration = 10, H(k+1, k) = 1.2317e-01 Magnitude Angle Growth Frequency Residual EV: 0 1.0000e+00 0.0000e+00 1.0701e-08 0.0000e+00 2.8913e-07 EV: 1 7.1131e-01 0.0000e+00 -3.4064e-01 0.0000e+00 6.8432e-05 Cheers Ankang 发件人:"Matt Duran" <matt.duran60(a)gmail.com> 发送时间:2021-03-15 08:33:45 (星期一) 收件人: Nektar-users(a)imperial.ac.uk 抄送: 主题: [Nektar-users] Residuals Stability Simulation This email from matt.duran60(a)gmail.com 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. Hello, I was running a stability simulation using the IncNavierStokesSolver and was wondering if there was some way to check or display the residuals after each iteration. Thank you for your time, Matt Duran Mechanical and Aerospace Engineering University of Central Florida

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white noise
by Alessandro Alberto de Lima 15 Mar '21

15 Mar '21

******************* 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. ******************* Hi Guys. Can you help me setting up a white noise during a few steps on m simulation? On the section 3.5.5 of the user guide I found this: <FORCE TYPE="Noise"> <WHITENOISE> [VALUE] <WHITENOISE/>  <UPDATEFREQ> [VALUE] <UPDATEFREQ/> <NSTEPS> [VALUE] <NSTEPS/> </FORCE> What's the meaning of those white noises? I need to specify one for each direction on three dimension problems? I need to assign that noise to a specific boundary region (a wall, for example)? Thank you. Alessandro

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Fieldconvert question
by Vidhi Zala 15 Mar '21

15 Mar '21

******************* 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. ******************* Hi all, I have limited experience with FieldConvert utility and need help with the module interppointdatatofld. Here is the way I am using it ./FieldConvert-g -m interppointdatatofld:frompts=tmp.pts compositemesh2d.xml file1.dat Is it possible to have the output as vtk/vtu file instead of .dat file? Most other modules in FieldConvert allow output as both .dat and .vtu. Any help will be appreciated! Thanks, V ,-~~-.___._. / | ' \ | |--------. Vidhi Zala ( ) 0 | | | School of Computing \_/-, ,----' | | | Scientific Computing and Imaging Institute ==== !_!-v---v--. University of Utah / \-'~; .--------. / __/~| ._-""|| | vidhi.zala(a)utah.edu =( _____|_|____||________| http://sci.utah.edu/people/vidhi.html I support Ruff Haven Crises Shelter for Homeless Pets <https://www.ruffhaven.org/donate>. Consider a donation today :)

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Residuals Stability Simulation
by Matt Duran 15 Mar '21

15 Mar '21

******************* 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. ******************* Hello, I was running a stability simulation using the IncNavierStokesSolver and was wondering if there was some way to check or display the residuals after each iteration. Thank you for your time, Matt Duran Mechanical and Aerospace Engineering University of Central Florida

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Roots of Jocobi or Legendre polynomial?
by Dongmyung Suh 07 Mar '21

07 Mar '21

******************* 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 a user of Nektar ++, and learning its foundation with Sherwin's book, Spectral hp element method for CFD [2ed]. I have a small question, while I study the book. When the book explains the Gauss-Lobatto-Legendre formula for integration (pg.61) and differentiation (pg 68), xi are the roots of Jocobi polynomial. However, in other references ( https://en.wikipedia.org/wiki/Gaussian_quadrature) they are the roots of Legendre polynomial. Which one is right? or both are correct? Please let me be clear about that. Thank you. Dongmyung Suh

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setting-up bc's for Compressible Navier-Stokes solver
by wasim sarwar 07 Mar '21

07 Mar '21

******************* 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, Good Morning, and wishing all of you very good day! I am trying to solve the problem of convergent-divergent nozzle with pressure at inlet and outlet. Does anyone have the idea how to setup the pressure inlet and pressure outlet boundary conditions in compressible Navier-Stokes solver. Also, give an idea of how-to setup the symmetry bc about x-axis. The input file is also attached herein for reference. Mant thanks in advance Wasim Sarwar UPC, Barcelona

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Turbulent channel flow test case
by Eli Frydman 07 Mar '21

07 Mar '21

******************* 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. ******************* Hi all, I tried to run the turbulent channel flow test case from the user guide (session file TurbChFl_3DH1D.xml) but i didn't get any turbulent flow. I used a body force in the u direction as explained and added also a perturbation in the spanwise direction and didn't get any transition. Regards, Eli

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simulation diverging during start-up
by Cimpoeru, Ionut Andrei 05 Mar '21

05 Mar '21

******************* 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. ******************* Hi everyone, I have a quad mesh generated in GMSH and then imported it in nectar using nekMesh. I am trying to run it using the incompressible solver 2D. I dropped to CFL considerably and the simulation is still diverging during startup at very low non dimensional time step 1e-8. Below are the expansion I am using using SVVcutoff=1 and Svvdivcoeff=0.5. I am trying to start the simulation using a low order as per my expansion and starting with a low Reynolds before I reach the actual conditions. The boundary conditions I am using are: Inflow>>>Dirichlet for Velocity and Von-Neumann for pressure Outlflow>>> Von-Neuman for velocity and Dirichlet for pressure using the Houtflow option Wall >>> using Dirichlet for velocity and von Neumann for pressure Are there any suggestions please? Thanks a lot and many thanks for any help. Cheers, Andrei <EXPANSIONS> <E COMPOSITE="C[100]" NUMMODES="3" FIELDS="u,v" TYPE="MODIFIED" /> <E COMPOSITE="C[100]" NUMMODES="2" FIELDS="p" TYPE="MODIFIEDQUADPLUS1" /> </EXPANSIONS> <SOLVERINFO> </SOLVERINFO> [cid:image002.jpg@01D711B6.D07C0DF0] Not Subject to Export Control This information is provided by Rolls-Royce in good faith based upon the latest information available to it; no warranty or representation is given; no contractual or other binding commitment is implied. (c) 2021 Rolls-Royce The data contained in, or attached to, this e-mail, may contain confidential information. If you have received it in error you should notify the sender immediately by reply e-mail, delete the message from your system and contact +44 (0) 3301235850 (Security Operations Centre) if you need assistance. Please do not copy it for any purpose, or disclose its contents to any other person. An e-mail response to this address may be subject to interception or monitoring for operational reasons or for lawful business practices. (c) 2021 Rolls-Royce plc Registered office: Kings Place, 3rd Floor 90 York Way, London, N1 9FX Company number: 1003142. Registered in England

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