November 2022 - Nektar-users

Re: [Nektar-users] Floquet stability analysis
by Abhishek Kumar 23 Nov '22

23 Nov '22

Excellent. With regards Abhishek On Mon, 21 Nov 2022 at 4:58 pm, <nandan.sarkar(a)iitkgp.ac.in> wrote: > Dear Sir, > > > > Thanks for the correction. The code is working now. > > > > Regards > > Nandan Sarkar > > > > *From:* Abhishek Kumar <abhishek.kir(a)gmail.com> > *Sent:* Monday, November 21, 2022 1:16 AM > *To:* nandan.sarkar(a)iitkgp.ac.in > *Cc:* nektar-users(a)imperial.ac.uk > *Subject:* Re: [Nektar-users] Floquet stability analysis > > > > Dear Nandan, > > > > I can see that there is an issue with your expansion definition. You are > missing the field "w". The correct expansion is as follows: > > > > *<EXPANSIONS>* > > *<E *COMPOSITE*=*"C[0]" NUMMODES*=*"7" TYPE*=*"GLL_LAGRANGE_SEM" > FIELDS*=*"u,v,w,p"* />* > > *</EXPANSIONS>* > > > > Also, remember to put "period" in the parameters. I have attached the XML > file, which I used to reproduce Barkley and Henderson, JFM, 1996. > > > > With regards > > Abhishek > > > > > --------------------------------------------------------------------------------------- > > Abhishek Kumar > > Assistant Professor (Research) > > Centre for Fluid and Complex Systems > > Coventry University, Coventry CV15FB > > Web: https://sites.google.com/view/abhishekkir > > > --------------------------------------------------------------------------------------- > > > > > > On Fri, Nov 18, 2022 at 9:55 AM <nandan.sarkar(a)iitkgp.ac.in> wrote: > > This email from nandan.sarkar(a)iitkgp.ac.in 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 trying to perform a Floquet stability analysis using Nektar++ but > facing some errors. I have generated a two-dimensional periodic base flow > of flow past a cylinder, at slices, and using the same in an XML file for > stability analysis. Below are the output and some relevant sections of the > XML file. It would be of great help to fix the issue or point to some > already set-up example cases for the Floquet stability analysis. > > > > #IncNavierStokesSolver Cylinder_Floquet.xml > > read base flow file Cylinder-Base_0.chk > > read base flow file Cylinder-Base_1.chk > > read base flow file Cylinder-Base_2.chk > > read base flow file Cylinder-Base_3.chk > > read base flow file Cylinder-Base_4.chk > > read base flow file Cylinder-Base_5.chk > > read base flow file Cylinder-Base_6.chk > > read base flow file Cylinder-Base_7.chk > > read base flow file Cylinder-Base_8.chk > > read base flow file Cylinder-Base_9.chk > > baseflow info : interpolation order 0, period 0.00111111, periodicity yes > > baseflow info : files from 0 to 9 (skip 1) with 10 time intervals > > Fatal : Level 0 assertion violation > > Expect to have three velocity fields with homogenous expansion > > > > XML file snippet: > > <SOLVERINFO> > > VALUE="VelocityCorrectionScheme"/> > > VALUE="UnsteadyNavierStokes" /> > > VALUE="Direct" /> > > VALUE="Galerkin" /> > > VALUE="IMEXOrder2" /> > > VALUE="HalfMode" /> > > VALUE="ModifiedArnoldi" /> > > VALUE="1D" /> > > </SOLVERINFO> > > <PARAMETERS> > > TimeStep = 0.001 > > NumSteps = 1000 > > IO_CheckSteps = 100 > > IO_InfoSteps = 100 > > Re = 188 > > Kinvis = 1./Re > > kdim = 4 > > nvec = 2 > > evtol = 1e-6 > > N_slices = 10 > > LZ = 2.4166 > > </PARAMETERS> > > <EXPANSIONS> > > <E COMPOSITE="C[0]" NUMMODES="7" FIELDS="u,v,p" > TYPE="GLL_LAGRANGE" /> > > </EXPANSIONS> > > > > Thank you in advance. > > > > Regards, > > Nandan Sarkar > > PhD candidate > > Dept. of Mechanical Engineering > > Indian Institute of Technology Kharagpur > > India 721302 > > _______________________________________________ > Nektar-users mailing list > Nektar-users(a)imperial.ac.uk > https://mailman.ic.ac.uk/mailman/listinfo/nektar-users > > > > > -- > > > -- Sent from IPhone

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Floquet stability analysis
by nandan.sarkar＠iitkgp.ac.in 20 Nov '22

20 Nov '22

******************* 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 trying to perform a Floquet stability analysis using Nektar++ but facing some errors. I have generated a two-dimensional periodic base flow of flow past a cylinder, at slices, and using the same in an XML file for stability analysis. Below are the output and some relevant sections of the XML file. It would be of great help to fix the issue or point to some already set-up example cases for the Floquet stability analysis. #IncNavierStokesSolver Cylinder_Floquet.xml read base flow file Cylinder-Base_0.chk read base flow file Cylinder-Base_1.chk read base flow file Cylinder-Base_2.chk read base flow file Cylinder-Base_3.chk read base flow file Cylinder-Base_4.chk read base flow file Cylinder-Base_5.chk read base flow file Cylinder-Base_6.chk read base flow file Cylinder-Base_7.chk read base flow file Cylinder-Base_8.chk read base flow file Cylinder-Base_9.chk baseflow info : interpolation order 0, period 0.00111111, periodicity yes baseflow info : files from 0 to 9 (skip 1) with 10 time intervals Fatal : Level 0 assertion violation Expect to have three velocity fields with homogenous expansion XML file snippet: <SOLVERINFO> </SOLVERINFO> <PARAMETERS> TimeStep = 0.001 NumSteps = 1000 IO_CheckSteps = 100 IO_InfoSteps = 100 Re = 188 Kinvis = 1./Re kdim = 4 nvec = 2 evtol = 1e-6 N_slices = 10 LZ = 2.4166 </PARAMETERS> <EXPANSIONS> <E COMPOSITE="C[0]" NUMMODES="7" FIELDS="u,v,p" TYPE="GLL_LAGRANGE" /> </EXPANSIONS> Thank you in advance. Regards, Nandan Sarkar PhD candidate Dept. of Mechanical Engineering Indian Institute of Technology Kharagpur India 721302

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Thick Strip Model
by 郭艳娇 20 Nov '22

20 Nov '22

******************* 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 teachers, I am a Ph.D. student. Recently, I went through a tutorial where finite-strip theory was used to model the VIV of flexible cables. I have a question: can I achieve a wind profile along the z-direction by changing the inflow conditions? for example, <REGIONREF="3"> <DVAR="u"VALUE="0.5*z"/> <DVAR="v"VALUE="0"/> <DVAR="w"VALUE="0"/> <NVAR="p"USERDEFINEDTYPE="H"VALUE="0"/ Regards | | 郭艳娇 | | fancyjiao(a)126.com |

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restart a solver in parallel
by m.r.rouhanian＠ut.ac.ir 20 Nov '22

20 Nov '22

******************* 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; When solving a problem in parallel with a restart file( e.g. restart.rst) as an initial condition I will encounter an error. I am using compressed binary output to solve the problem in parallel. I think this is because the .xml file depends on the number of cores converted to a smaller domain for each processor. However, the restart file contains field data for the entire domain. How can I restart a solver in parallel? Any comments would be appreciated. Best regards, Mohammad

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Constant CFL number
by Mahdi Erfanian Nakhchi 19 Nov '22

19 Nov '22

******************* 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 running some 3D incompressible simulations. The problem I faced is that the software gives me identical CFL numbers for all time steps. Also, the simulation results do not change with time, which is not correct. The flow is turbulent and the Reynolds number is 10000. Steps: 20 Time: 2e-06 CPU Time: 8.2572s CFL: 0.338963 (in elmt 105130) Steps: 30 Time: 3e-06 CPU Time: 7.98256s CFL: 0.338963 (in elmt 105130) Steps: 40 Time: 4e-06 CPU Time: 7.94238s CFL: 0.338963 (in elmt 105130) Steps: 50 Time: 5e-06 CPU Time: 7.99028s CFL: 0.338963 (in elmt 105130) Steps: 60 Time: 6e-06 CPU Time: 8.02182s CFL: 0.338963 (in elmt 105130) Steps: 70 Time: 7e-06 CPU Time: 8.03556s Have you ever faced this issue? and any solutions for that? Many thanks. Best regards Mahdi This message is intended solely for the addressee and may contain confidential and/or legally privileged information. Any use, disclosure or reproduction without the sender's explicit consent is unauthorised and may be unlawful. If you have received this message in error, please notify Northumbria University immediately and permanently delete it. Any views or opinions expressed in this message are solely those of the author and do not necessarily represent those of the University. Northumbria University email is provided by Microsoft Office365 and is hosted within the EEA, although some information may be replicated globally for backup purposes. The University cannot guarantee that this message or any attachment is virus free or has not been intercepted and/or amended.

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Visit with Nektar++ format reader
by Stanislaw Gepner 14 Nov '22

14 Nov '22

******************* 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, Has anyone been successful in using Nektar++ format for direct visualization with Visit? I managed to compile visit with Nektar++ support but I am unable to read in data that use Homogeneous expansion. The reader issues an error and in the command line from which I invoke Visit I see what seems like a Nektar++ message stating "HomModesZ/npz should be an even integer." like if I would be using the parallel strip version. So, does anyone knows if the implementation that Visit uses is capable of Homogeneous1D? Cheers, Stan -- Pozdrawiam, dr inż. Stanisław Gepner, *Wydział Mechaniczny Energetyki i Lotnictwa* Nowowiejska 21/25 Str. 00-665 Warszawa, Polska tel. +48 (22) 234 51 70 <http://www.pw.edu.pl/>

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Mesh Conversion from Gmsh using NekMesh
by İlteber Özdemir 08 Nov '22

08 Nov '22

******************* 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, I am trying to convert a simple mesh made in Gmsh (cyl.msh) to Nektar++ usable format (.xml). I can view the mesh in Gmsh. NekMesh gives the following error when I try to convert: NekMesh -v cyl.msh out.xml [InputGmsh] Reading Gmsh file: 'cyl.msh' [InputGmsh] Finished reading mesh. [InputGmsh] - Element dimension : 0 [InputGmsh] - Space dimension : 2 [InputGmsh] - No. of nodes : 0 [InputGmsh] - No. of 0D elements : 0 [InputGmsh] - No. of boundary elements : 0 [InputGmsh] - Elapsed time: 0.0542657s. [OutputNekpp] Writing Nektar++ file 'out.xml' Fatal : Level 0 assertion violation Unable to read composite index range: terminate called after throwing an instance of 'Nektar::ErrorUtil::NekError' what(): Level 0 assertion violation Unable to read composite index range: Aborted Can you help me with this problem? With kind regards, Ilteber -- İlteber R. Özdemir

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Assemble the output files when using mpirun
by m.r.rouhanian＠ut.ac.ir 06 Nov '22

06 Nov '22

******************* 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; When I use the mpirun command to run a solver, dependent on the number of cores, chk format files produce (e.g. *_P0.chk, *_P1.chk, *_P2.chk, ...). Is there any way to assemble all of these .chk files and reconstruct a single output file containing all domain information? Best Regards, Mohammad

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Variable or temperature dependent viscosity
by Debbahi Saad 05 Nov '22

05 Nov '22

******************* 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'm using Nektar++ Incompressible Navier-Stokes Solver in fully 3D mode, with added temperature field, in a plane poiseuille flow heated at the bottom wall, solver running very well, and as if it wasn't already enough, I'm asking for more here ! 'hopefully', --> My question is about the possibility to handle variable viscosity or temperature dependent viscosity, So is there any approach to account for temperature dependent viscosity nu(T) ? I'm asking for this, since the temperature gradient at the heated wall is known to alter the viscosity (Ref: Physics of transitional shear flow, A. V. Boiko et al. Sec. 6.5 page 112) which I have to account for when carrying flow transition calculations. --> In case it is not directly achievable through Nektar's functionalities, is it conceivable to direct my effort toward employing an ad-hoc approach modifying the momentum transfer to account for lower liquid viscosity at higher temperature? That is, most likely adding a forcing term which mimics the effect of varying viscosity by altering the momentum transfer accordingly, since the stress tensor for a newtonian fluid tau=mu.du/dy. Any comment on the sanity of this approach ? Thank you all in advance, any help or general guidelines on this model variation greatly appreciated. Regards, Saad

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About combustion module
by Chengeng Qian 04 Nov '22

04 Nov '22

******************* 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, I am a beginner of Nektar++. I note that there is a lecture named *Development of a Combustion Module within the Nektar++ Framework *in the Nektar++ Workshop 2022. However, I didn't see any examples of combustion simulation in the tutorials. Is there someone know how to use combustion module in Nektar++? Regrads Chengeng

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