December 2019 - Nektar-users

Element with max CFL
by Vishal Saini 02 Apr '20

02 Apr '20

Hi all, Quick question: Has anyone tried to check the location of a particular element in the mesh? A log file reports the maximum (?) CFL and the corresponding element as: "CFL: 0.0337915 (in elmt 94488)"? Is there a quick way to locate "elmt 94488"? Cheers, Vishal

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Manipulate 3DH1 chk/fld file in Fourier space
by F Mellibovsky 16 Mar '20

16 Mar '20

Dear all, I have run a 3DH1 simulation and I need to set all Fourier coefficients to zero except those corresponding to a fundamental wavelength and its harmonics (e.g. keep only modes 0, +-5, +-10, etc and set all the rest to zero). I have the intuition that some combination of FieldConvert options can accomplish exactly this, but I am unsure of what is the best (or some) way to proceed. My guess is that the "homplane:wavespace:planeid=?" can be used to extract the individual Fourier modes, but I am unsure as to how the Fourier modes are sorted and which ones must be extracted to recover a chosen fundamental wavelength and its harmonics (both real and imaginary parts, or modulus and argument, or however the Fourier modes are stored). The only one I'm pretty sure of is mode 0 or mean mode. Once I get the individual fld files for each one of the modes, I was intending to use the "addfld:fromfld=mode1.fld:scale=1 mode1.xml mode2.fld newfile.fld" sequentially to build a solution from the chosen modes. The issue here is that the fields extracted with "homplane" seem to be 2D and would therefore need to be recast in 3DH1 form before proceeding to "addfld". How can this be done? Thanks in advance for your help Fer Mellibovksy

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r-adaptation
by 蒋树杰 05 Jan '20

05 Jan '20

******************* This email from 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, Now I want to use Nektar++ to do some transonic simulation (Compressible Solver). I want to increase the resolution for shocks. I find a PDF named 'Mesh adaptation (r & p) for compressible flows in Nektar++', given by Joaquim Peiro et al. They mentioned r-adaptation can be used by clustering nodes near shocks. But I can not find more information about this. Is this function available in Nektar++ 5.0.0? If someone is familiar with this, please let me know. Merry Christmas! Thank you for your help! Shujie University of Southampton

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Field Interpolation during runtime
by Nitish Arya 05 Jan '20

05 Jan '20

******************* This email from 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 want to perform an aeroacoustic simulation in which I am using APESolver (nektar-4.4.1). I am transferring the source terms from the fluid solver (OpenFoam) to nektar++. I need to interpolate the source terms from the finite volume mesh (which is relatively coarser) ino the spectral mesh which can be used by APESolver. Initially, I used Shepard's algorithm to interpolate the source terms which performed well for serial runs but, unfortunately, there are several numerical errors when I am passing the data using multiple processors. Recently I found out that there is an already available utility in nektar++ for field interpolation ( as post-processing utility). I wanted to inquire if it is possible to use the functionality for interpolating the data during runtime with multiple processors. Happy new Year to all of you!! regards, Nitish Arya Department of Aerospace Engineering IIT Kanpur, India

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Nektar++ question
by Moto Light 20 Dec '19

20 Dec '19

******************* This email from 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 usaers, Now i have a problem in Nektar, i did a Floquet analysis study using Nektar, it is working fine and the results looks fine, when i am doing this i am just using two modes mode 0 and mode 1, mode 0 is the 2D filed and mode 1 is the 3D expansion, do you have an idea about how i can extract mode 1 from my solved field file?? I tried something but i am not sure it is fine: I used the meanmode module to extract mode zero as a 2D field results from the complete field using this: *FieldConvert -m meanmode file.xml file.fld file-mean.fld* after i used this 2D field to be a 3D by expand it with the same Lz and the same number of modes of my complete case but also putting w=zero After iI used Addition (( to used as a subtraction using scale -1)) *FieldConvert -m addfld:fromfld=modified_mode0.fld:scale=-1 file1.xml complete_field.fld output_field.fld* *and the results like a 3D mode 1 * *do you think this way is ok???* *==============* Thank you in advance, and i wish all of you have a great day. Regards, *Reda El Mansy* PhD candidate Department of Aeronautics UPC Department of Aeronautics

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Nektar++ question
by Josuel Kruppa Rogenski 05 Dec '19

05 Dec '19

******************* This email from josuelkr(a)gmail.com originated outside Imperial. ******************* Dear Nektar users, I am doing some tests using IncNavierStokes solver + steady driver (with default parameters) + periodic boundary conditions. I wonder if someone has to take some extra care if one of the boundaries is similar to a sawtooth wave, as an example. Specifically, I took initially a 2D-Couette flow. After that, I substituted one of the flat walls to a tilted small square step. Results seems to be nonphysical. I played with different meshes and time integration methods but could not draw any conclusion. My .xml file solver info is: <SOLVERINFO> </SOLVERINFO> <EXPANSIONS> <E COMPOSITE="C[0]" NUMMODES="12" TYPE="MODIFIED" FIELDS="u,v,p" /> </EXPANSIONS> Any help would be appreciated. Thank you in advance, J PS: I can provide .xml and .geo files I am working with if necessary.

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Floqueat analysis Mode1 problem
by Moto Light 04 Dec '19

04 Dec '19

******************* This email from redamansyhh(a)gmail.com originated outside Imperial. ******************* Hi All, Now i have a problem in Nektar, i did a Floquet analysis study using Nektar, it is working fine and the results looks fine, when i am doing this i am just using two modes mode 0 and mode 1, mode 0 is the 2D filed and mode 1 is the 3D expansion, do you have an idea about how i can extract mode 1 from my solved field file?? I tried something but i am not sure it is fine: I used the meanmode module to extract mode zero as a 2D field results from the complete field using this: *FieldConvert -m meanmode file.xml file.fld file-mean.fld* after i used this 2D field to be a 3D by expand it with the same Lz and the same number of modes of my complete case but also putting w=zero After iI used Addition (( to used as a subtraction using scale -1)) *FieldConvert -m addfld:fromfld=modified_mode0.fld:scale=-1 file1.xml complete_field.fld output_field.fld* *and the results like a 3D mode 1 * *do you think this way is ok???* *==============* Thank you in advance, and i wish all of you have a great day. Regards, *Reda El Mansy* PhD candidate Department of Aeronautics UPC Department of Aeronautics

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(no subject)
by A.P. 04 Dec '19

04 Dec '19

******************* This email from k210(a)list.ru originated outside Imperial. ******************* Hello, is it impossible to use u,v,w in the forcing expressions like this </CONDITIONS> … <FUNCTION NAME="MyForce"> <E VAR="u" VALUE="v+u" /> <E VAR="v" VALUE="1.0" /> </FUNCTION> ... </CONDITIONS> <FORCING> <FORCE TYPE="Body"> <BODYFORCE> MyForce </BODYFORCE> </FORCE> </FORCING> ? Alexander Proskurin

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