February 2016 - Nektar-users

Porous Region in nektar++
by 张宾 01 Mar '16

01 Mar '16

Dear all We are using nektar to calculate multiple outlets flow problem, and porous region is required in the simulation. In my opinion, when the porous region is applied in computational domain, inertial resistance coefficients and viscous resistance coefficients should be set for the porous region. Is there any instructions that tell us how to set these two coefficients in Condition section of XML session file, or are there other ways to use porous region in nektar++? Best regards, Bin

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How to figure out each Face's Expansion Coefficients given ElementExpansion Coeffcients
by ashok jallepalli 01 Mar '16

01 Mar '16

Dear All, I am trying to do the following in my code. I am stuck with not being able to few steps. Can you please suggest if there are any api calls which I can use. Or areas of code which does the same. Take Multi-region element, Loop through each element in the multi region. Loop through each face of element of multi region. Get 2D element expansion of each face and its coefficients. End each face loop. End each element loop. Question(1) To get the 2D element expansion, I am able to use GetfaceExp() on Expansion3D. This only works for boundary elements when the field is Cont3DExp. When element is not in the boundary it gives a segmentation fault 11. - Is this supposed to work ? Question(2) I can overcome the above problem by initializing the field as DisCont3DExp, while loading from fld file. (This seems to work for now). - Is there a function to get each face's Expansion coefficients from element expansion coefficients ? - Or should I dynamically check if the element is Hex, Tet, prism and try to figure out from the mapping order? Thank you,

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Nektar++ User Workshop 2016
by Sherwin, Spencer J 27 Feb '16

27 Feb '16

Hi, Following the success of our inaugural workshop last year we are planning to run it again this year on June 7th/8th. Please see a provisional outline under http://www.nektar.info/community/workshops/nektar-2016/ If you are interested in attending could we request that you register under the web page so we can get an idea of numbers. We would also be very interested in hearing about whether you would like to attend an introductory or advanced satellite session. Best regards, Spencer. 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(a)imperial.ac.uk +44 (0) 20 759 45052

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Implicit LES in Nektar++
by Kamil ÖZDEN 27 Feb '16

27 Feb '16

Dear All, I want to run Implicit Large Eddy Simulations by using Nektar++. As far as I know from some studies in literature (i. e. http://arxiv.org/pdf/1507.06012.pdf) it is possible to do such simulations in Nektar++. However, I couldn't find any detail about it in the user guide. Is there any document (tutorial etc.) that shows how to run such simulations in Nektar++? Best Regards, Kamil --- Bu e-posta virüslere karşı Avast antivirüs yazılımı tarafından kontrol edilmiştir. https://www.avast.com/antivirus

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Nectar-Developer: Find each element's coefficients from ExpList
by ashok jallepalli 15 Feb '16

15 Feb '16

Hi everyone, I currently working on a project and would like to do the following task and need some guidance. (1) Read an .fld file. (2) Load it into vector fields into expansions (exp_u, exp_v, exp_w) (3) Loop through each element in the mesh and do some processing in it and store the result in a new expansion. I have a problem in step (3). I am able loop through each expansion but unable to understand how should I retrieve coefficients for each element. Array<OneD,NekDouble> gcoeff = exp_u->GetCoeffs() - This gets me the coefficients of whole expansion. How do I match coefficients which belong to each element. These two statements used in the code seem to reorder the coefficients in the expansion, Can someone explain what they are doing. Exp_u->GlobalToLocal() Exp_u->LocalToGlobal() Would any of these functions reorder coefficients elementwise. So that I use access element[i]'s coefficients as gcoeff[I*numOfCoeffPerEle]. Ashok.

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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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EulerCFD in 1D with variable coefficients in mass and stiffness matrix
by Kühnelt Helmut 08 Feb '16

08 Feb '16

Dear Spencer, How can I implement or modify the EulerCFE code (only 1D is needed) to obtain a variant with mass and stiffness matrices with variable coefficients (i.e. M_A = \int_{-1}^{1} L_q L_p A(\xi,t) d\xi), as well as setting up similar matrices with variable coefficients for setting up source terms (e.g. M_s S_p). Best regards, Helmut

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Changelog file
by David Moxey 07 Feb '16

07 Feb '16

Dear all, A quick note for you all; the latest master incorporates a CHANGELOG.md file, which catalogs changes as we develop the code. In order to keep things update, can I ask that, once you submit a merge request, you just add a short description of your change to the file and put a reference to the merge request number. Hopefully the layout should be self-explanatory, but if not 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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Compressed format for XML files
by Sherwin, Spencer J 07 Feb '16

07 Feb '16

Hi, We have just merged into master a modification where the input mesh files produced by MeshConvert will be stored in a compressed format to make large input files much smaller and to also help with the start up and processing of input files since previously they were read in a very verbose format. This does mean however that input files sections of Vertices, Edges, Faces, Elements and Curves are no longer directly readable. If you wish to see an ascii format file you need to add :xml:uncompress to the end of the .xml file, i.e. MeshConvert file.msh out.xml:xml:uncompress There is also documentation in the User-guide of the master version. Please let us know if you have any problems with this option. Best regards, Spencer. 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(a)imperial.ac.uk<mailto:s.sherwin@imperial.ac.uk> +44 (0) 20 759 45052

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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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