August 2018 - Nek5000-users - mailman3.cels.anl.gov

Regarding spatial resolution
by nek5000-users＠lists.mcs.anl.gov 23 Aug '18

23 Aug '18

Hey Neks, I have a very basic question about the spatial resolution of Nek5000. Suppose my elements in the domain are squares of unit length. If my GLL points used are 17 (or order of the polynomial used is 16), what is the least spatial length resolved by the code? As an approximate, can one use 1/17 units? Is there a way to calculate this least spatial length being resolved? Thanks, Saikat

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Channel Flow 1D/2D energy spectra
by nek5000-users＠lists.mcs.anl.gov 21 Aug '18

21 Aug '18

Hi Nek Users, I am a new user to Nek5000 and I have been playing around with the channel flow example. I have set up an example similar to Kim and Moin. The mean velocity profile seems to agree quite well so I have set up the initial case correctly. Now, my goal is to try and recreate the energy spectra as in the paper above. I am confused as to the best way to go about this, would it be best to obtain output files then do the post processing outside of Nek or can it be done inside Nek as well? My ultimate goal is to be able to cut off some of the higher energy modes and transform it back and feed it at the start of the simulation. Any advice on this would be appreciated as I have been struggling as to how I should proceed in Nek5000. Thanks in advance, David

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Exodus II to Nek
by nek5000-users＠lists.mcs.anl.gov 20 Aug '18

20 Aug '18

Thanks a lot. Another question please, I am using periodic BC at the ends of the pipe. Is the periodic BC satisfied exactly for all three components of the velocity as it is supposed to? Hint, the flow is not laminar. Ali

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Exodus II to Nek
by nek5000-users＠lists.mcs.anl.gov 20 Aug '18

20 Aug '18

Yes, I assume that was done successfully. Thanks, Ali

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Exodus II to Nek
by nek5000-users＠lists.mcs.anl.gov 19 Aug '18

19 Aug '18

What are you trying to do? I am just trying to convert exodus ii mesh format to rea. Did you modify the source? Sorry, what source did you mean? I can run all Nek5000 files with no problems. Only exo2nek.f is not working. What happens if you run „maketools exo2nek“? netcdf ,seacas-exodus, and other files, e.g. exo2nek.o, have been installed. Also, after the compilation process finishes, some warnings appear like "Type mismatch in argument ‘j’ at (1); passed INTEGER(4) to REAL(8)" or something like that. That is all I know. Again thanks for your help, Ali

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Exodus II to Nek
by nek5000-users＠lists.mcs.anl.gov 19 Aug '18

19 Aug '18

Thank you for bringing this to my attention, ( ./maketools exo2nek.f) is done successfully now by using Nek5000 v17. However, I still struggle with its implementation on my Exodus II mesh. I am writing (gfortran -c exo2nek.f ) and the following error comes up: Warning: exo2nek.f:3: Illegal preprocessor directive Warning: exo2nek.f:14: Illegal preprocessor directive exo2nek.f:42: Error: Can't open included file 'exodusII.inc'. Is my way of using exo2nek.f correct? Ali Embry-Riddle Aeronautical University

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Exodus II to Nek
by nek5000-users＠lists.mcs.anl.gov 18 Aug '18

18 Aug '18

Hello Everyone, I was trying to convert 3-D Exodus II mesh to Nek. I found the following script: exo2nek.f in my files of Nek5000. When I ran it, I got this Error: Can't open included file 'exodusII.inc'. After that, I made ./maketools exo2nek, and then I got the following: makefile:21: recipe for target 'exo2nek.o' failed make[1]: *** [exo2nek.o] Error 1 make[1]: Leaving directory '/home/abdulra5/nek5_svn/trunk/tools/exo2nek' makefile:4: recipe for target 'all' failed make: *** [all] Error 1 Can anybody tell me what are the right steps for conversion? And, If my steps are correct, how can I fix the above issues? Many thanks, Ali Embry-Riddle Aeronautical University

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reshape array
by nek5000-users＠lists.mcs.anl.gov 15 Aug '18

15 Aug '18

Hi all, All average streamwise velocity are stored in this array "common /avg/ uavg(lx1,ly1,lz1,lelv)" but I want this array to be reshaped into "common /abcd/ abcd(lx1*ly1*lz1,lelv)" The following didn't work: common /avg/ uavg(lx1,ly1,lz1,lelv) common /abcd/ abcd(lx1*ly1*lz1,lelv) abcd=reshape(uavg,(/ lx1*ly1*lz1,lelv /)) This is how array reshaping works in fortran. Unfortunately, didn't work in nek. Anyone knows why? Many thanks in advance for your replies.

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Freestream BC
by nek5000-users＠lists.mcs.anl.gov 14 Aug '18

14 Aug '18

Dear Nek users, I am wondering if freestream BC is available in the NEK5000? Coz I would like to run the Falkner-Skan BL using the Nek. I notice two convective BCs are ready to use, ‘O’ and ‘ON’. But I do not think they are appropriate for the FSBL. Thanks for your help in advance

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Calculate Velocity Fluctuation Fields
by nek5000-users＠lists.mcs.anl.gov 10 Aug '18

10 Aug '18

Hi Neks, I have read many entries in the archives regarding the way to calculate instantaneous fluctuations in velocity field, but I'm still unsure of the last steps to archive this. I understand that this is the workflow: 1) Running a case and call avg_all in usrchk() to get avg (<u_i>), rms (<u_i*u_i>) and rm2 (<u_i*u_j>) files. 2) Create a file with .list extension to load in post-processing mode these results with this format: ------------------------- <number of files> avg***0.f00001 avg***0.f00002 . . . avg***0.f****** ------------------------- 3) Set NSTEPS = 0 to enable post-processing mode. 4) Load in usrchk() the avg_all files with 'load_fld'. 5) Calculate u_i' = u_i - <u_i> 6) Output the fluctuation fields call outpost(vx',vy',vz',pr,t,'***') How should I perform the 4th and 5th steps? Best regards, *Nicolás*

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