January 2016 - Nektar-users

Parallel transposition not implemented yet for 3D-Homo-2D approach
by ceeao 14 Feb '16

14 Feb '16

Dear all, I just installed the library, and need to simulate DNS of a channel flow with oscillating pressure gradient. As I have two homogeneous directions I applied standard Fourier discretization in these directions. It seems like this case is not parallelized yet, and I got the error in the subject. I was wondering if I'm overlooking something. If not, are there maybe any plans in the future to include parallelization of 2D FFT's? Thank you in advance. Best, Asim Onder Research Fellow National University of Singapore ________________________________ Important: This email is confidential and may be privileged. If you are not the intended recipient, please delete it and notify us immediately; you should not copy or use it for any purpose, nor disclose its contents to any other person. Thank you.

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Logfile for Nektar
by Amitvikram Dutta 02 Feb '16

02 Feb '16

Hi, Is there some form of a logfile implementation for Nektar++ which one can query as a simulation is proceeding in order to monitor convergence? Sincerely,

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Nektar++ 4.2.0 and Nektar++ 3.2.0 compatibility issues
by Amitvikram Dutta 02 Feb '16

02 Feb '16

Hi, I've been using Nektar++ for DNS studies of Laminar Separation Bubbles over airfoils. So far I've been running Nektar++4.2.0 on my personal workstation. However, now that I am dealing with meshes containing more than 200k elements, I'll start submitting jobs to a cluster. The cluster however has Nektar++3.2.0 installed. Might there be any compatibility issues for the cases that I have been running so far? I have been using the IncNavierStokesSolver with Galerkin projection and a time-integration method of IMEXOrder2. Sincerely, *Amitvikram Dutta* *MASc Candidate* *Graduate Research Assistant * *Okanagan CFD Laboratory* *University of British Columbia | Okanagan Campus*

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ExpList::SmoothField produces artifacts
by Kilian Lackhove 01 Feb '16

01 Feb '16

Dear all, I want to create a C0-continuous field from interpolated input data. The input field is obtained from a FVM code and was filtered with a gaussian in space and interpolated to the quadrature points. I store the field in a ContField2D m_bf = Array<OneD, MultiRegions::ExpListSharedPtr>(m_spacedim + 2); m_bf[i] = MemoryManager<MultiRegions::ContField2D>::AllocateSharedPtr(m_session, m_graph); copy the interpolated data into its m_phys array Vmath::Vcopy(nq, filteredField[i], 1, m_bf[i]->UpdatePhys(), 1); and then try to smooth the field. Until now, i just did: m_bf[i]->IProductWRTBase(m_bf[i]->GetPhys(), m_bf[i]->UpdateCoeffs()); m_bf[i]->MultiplyByElmtInvMass(m_bf[i]->GetCoeffs(), m_bf[i]->UpdateCoeffs()); m_bf[i]->BwdTrans(m_bf[i]->GetCoeffs(), m_bf[i]->UpdatePhys()); which yields the field depicted in DG.png. However, this does not ensure C0- continuity, so i tried to call ExpList::SmoothField afterward: m_bf[i]->SmoothField(m_bf[i]->UpdatePhys()); However, this produces a distorted field as shown in smoothed.png. I am using a 6th order modified expansion basis: <E COMPOSITE="C[10]" NUMMODES="6" FIELDS="p,u,v,w" TYPE="MODIFIED"/> and the mesh is depicted in smoothed_mesh.png. What is the cause of this problem and what can i do do fix it? Cheers, Kilian -- Kilian Lackhove, M.Sc. Fachgebiet für Energie- und Kraftwerkstechnik L1|08 114 Technische Universität Darmstadt Jovanka-Bontschits-Straße 2 D-64287 Darmstadt Germany Tel.: +49 6151 16 - 28915 Fax: +49 6151 16 - 6555 e-mail: lackhove(a)ekt.tu-darmstadt.de

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Linear stability analysis of a three-dimensional baseflow
by Siddarth Chintamani 20 Jan '16

20 Jan '16

Hello, I am trying to perform stability analysis of linearized incompressible Navier Stokes equation of a three-dimensional baseflow. I understand that Nektar++ capabilities for stability analysis are limited to 2D or Quasi3D baseflow representation. Unfortunately, my problem has to be solved as 3D. Is there any way to relax the 2D or quasi3D representation? Any help will be greatly appreciated. Thank you, Siddarth Chintamani

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10e5 Re 2D flow over NACA airfoil
by Amitvikram Dutta 19 Jan '16

19 Jan '16

Hi all, I'm trying to compare the results obtained for flow over a NACA 0018 airfoil for both traditional FVM solvers (in my case OpenFOAM) and an hp solver like nektar++. I was wondering what the most appropriate case from the test directory that I could modify for my use vis-a-vis solver properties would be? I have already obtained the mesh from gmsh and used MeshConvert to obtain the appropriate .xml file. Do the physical lines as defined on the original .geo file map in the same manner as composites to the .xml file? i.e. Would Physical Line 1 from gmsh Translate to Composite 1 in the .xml file the MeshConvert outputs? Sincerely, *Amitvikram Dutta* *MASc Candidate* *Graduate Research Assistant * *Okanagan CFD Laboratory* *University of British Columbia | Okanagan Campus*

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Convergence problem in constricted pipe flow problem
by Kamil ÖZDEN 16 Jan '16

16 Jan '16

Dear All, I'm trying to run a constricted pipe flow problem at Re=1000 in Nektar++ with the following boundary conditions: <BOUNDARYREGIONS> C[6]  C[8]  C[7]  </BOUNDARYREGIONS> <BOUNDARYCONDITIONS> <REGION REF="0"> <D VAR="u" VALUE="2*(1-(4*(y^2+z^2)))" /> <D VAR="v" VALUE="0" /> <D VAR="w" VALUE="0" /> <N VAR="p" USERDEFINEDTYPE="H" VALUE="0" /> </REGION> <REGION REF="1"> <N VAR="u" VALUE="0" /> <N VAR="v" VALUE="0" /> <N VAR="w" VALUE="0" /> <D VAR="p" VALUE="0" /> </REGION> <REGION REF="2"> <D VAR="u" VALUE="0" /> <D VAR="v" VALUE="0" /> <D VAR="w" VALUE="0" /> <N VAR="p" USERDEFINEDTYPE="H" VALUE="0" /> </REGION> </BOUNDARYCONDITIONS> The simulation seems converging but after a while starts to diverge and ended by Nektar due to exceedence of maximum iteration number. Time history plot of a node at the center of the pipe is attached to the mail. Does anybody have idea about the source of this problem? Is it directly related with the structure of the mesh I've used or do I set something wrong in my *.xml file? Best Regards, Kamil --- Bu e-posta virüslere karşı Avast antivirüs yazılımı tarafından kontrol edilmiştir. https://www.avast.com/antivirus

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Running first Nektar case after installation
by Amitvikram Dutta 14 Jan '16

14 Jan '16

Hi all, New Nektar user here. So, I've successfully managed to install Nektar++4.2.0 on my machine. The Ctest results are 100% and I assume nektar is up and running. The only problem is, when I download the basic Cyl case and try to run it, it seem the system does not recognize "nektar" as a valid command. To be clear, in a folder containing the files cyl.rea and cyl.rst, I tried the following command nektar -V cyl.rea I got the following response If 'nektar' is not a typo you can use command-not-found to lookup the package that contains it, like this: cnf nektar *Any help would be greatly appreciated. * ** *Sincerely,* *Amitvikram Dutta* *MASc Candidate* *Graduate Research Assistant * *Okanagan CFD Laboratory* *University of British Columbia | Okanagan Campus*

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Gitlab update, 9th January
by David Moxey 10 Jan '16

10 Jan '16

Dear all, Happy new year! Just a quick email to let you know that I plan to take our Gitlab instance offline for a quick upgrade of the software that covers the usual security fixes. Currently I've planned this for the morning of the 9th of January (this Saturday). If you have any issues with the date then please let me know! Cheers, Dave -- David Moxey (Research Associate) d.moxey(a)imperial.ac.uk | www.imperial.ac.uk/people/d.moxey Room 363, Department of Aeronautics, Imperial College London, London, SW7 2AZ, UK.

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