November 2017 - Nek5000-users - mailman3.cels.anl.gov

Hackathon Update
by nek5000-users＠lists.mcs.anl.gov 10 Nov '17

10 Nov '17

Dear All, There are currently about 20 registrants for the upcoming Hackathon, which starts Sunday, November 12 at 1 PM in 4405 Siebel Hall at the University of Illinois, Urbana Champaign. (This is the UIUC computer science building, 4th floor.) It's still not too late to sign up. If you wish to join, please register so that we can have an accurate head count for the meals. Parking is free on Sunday, so you can park most anywhere near Siebel. Sunday evening dinner will be at Pizza M in Urbana - a 13 minute walk from Siebel. Monday and Tuesday we will meet at 9 AM in the first floor of the NCSA building, which is next door to Siebel. As mentioned in an earlier post, we'd like to start off with people taking a two or three minutes to stand up and describe the problem they'd like to tackle during the hackathon (e.g., particle tracking, turbulence in a given domain, etc.) so that we can self organize into small focus groups. Also, we'll have a few requests from the development team for assistance with certain tasks aimed toward getting out the latest release and with developing new examples to be posted. Looking forward to seeing you all on Sunday! The Nek development team.

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genmap error
by nek5000-users＠lists.mcs.anl.gov 10 Nov '17

10 Nov '17

Hey neks, I'm having a wierd genmap error while trying to convert from a gmsh format to nek format using cpraveen's script. The .rea file generates correctly but I cannot run genmap after that. trying to compile the case without running genmap also gives an error. The error message from genmap is ERROR: error reading 1 1 891 aborting 510 in routine rdbdry. I can email the .geo and .msh files if required Sincerely, -- *Amitvikram Dutta* Graduate Research Assistant Fluid Mechanics Research Lab University of Waterloo

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Re: [Nek5000-users] Problem with drag coefficient of ext_cyl
by nek5000-users＠lists.mcs.anl.gov 08 Nov '17

08 Nov '17

Hi SIjo George, Can you tell how have you changed the domain? Also, are you running the latest version of the repo? When I use the current case in NekExamples repo - ext_cyl - and run the calculation, I get a drag coefficient of about 1.35 for Re=100, which I think is about right for this Re. Below is a plot of drag coefficient evolution over time that I got. Ketan [cid:B3193C5A-4983-41E9-B997-E058759EA923]

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Problem with drag coefficient of ext_cyl
by nek5000-users＠lists.mcs.anl.gov 08 Nov '17

08 Nov '17

Hello, I just started my PhD work in FSI of NACA profile so I am using NEK5000 for the simulations. So, in order to start with NEK5000, first I try to validate a very simple test case which is the flow around a 2D cylinder. This test case is already in the example folder of the solver kit. So, I try to simply run the test case and tried to compare the drag coefficient with the given Re number. It was giving a wrong value. for example it gives 21 instead of 3.5 for Re 100. I had changed the domain a bit according the research papper I have. I used torque calc function to compute the drag. Could you please help me to validate this test case? So that I can continue with lmy moving cylinder test case and I will be more confident in NEK5000 Thanks SIjo George

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Dissipation rate
by nek5000-users＠lists.mcs.anl.gov 08 Nov '17

08 Nov '17

Dear Neks, I would like to compute the turbulent dissipation rate, in order to calculate the Kolmogorov microscales. Does a subroutine already exist or should I compute it from userchk ? Thank you very much for your answers, Samuel

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IFCHAR option in rea file
by nek5000-users＠lists.mcs.anl.gov 06 Nov '17

06 Nov '17

Hello, I have been using IFCHAR = TRUE in my simulations. The CFL number is around 1.2 and the computations appear to go on nicely. I would like to know if the flow field computed using IFCHAR=TRUE option is different than the one obtained with IFCHAR=FALSE (albeit with smaller dt)? If yes, can the difference be significant? Many thanks, NN

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Axis in spectral elements
by nek5000-users＠lists.mcs.anl.gov 06 Nov '17

06 Nov '17

Hi, Neks! I am working with a complex geometry and want to change positions of some points in spectral elements. I've read in documentation that i,j,k,e in xm1(i,j,k,e), for example, are changed from 1 to nx1,ny1,nz1 and nelv respectively. But during my tests it's seemed that in different elements x,y,z axis not always correspond to the global coordinate system. Am I right? And how could I change only the lowest slice of an element, for example? Best regards, Elizabeth

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Hackathon
by nek5000-users＠lists.mcs.anl.gov 06 Nov '17

06 Nov '17

Dear All, Just a reminder to sign up for the upcoming Hackathon at UIUC, this coming Sunday--Tuesday (11/12--11/14), if you plan to attend. Here is the link: https://doodle.com/poll/yxxtw49ewxtzzruk In addition to helping attendees with their challenging problems, we also are asking attendees to develop an example case (with a known solution, if possible) appropriate for posting to the Examples suite. Our goal is to have the examples posted by Tuesday. Looking forward to seeing you next Sunday! The Nek development team.

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Axis in spectral elements
by nek5000-users＠lists.mcs.anl.gov 01 Nov '17

01 Nov '17

Hi, Neks! I am working with a complex geometry and want to change positions of some points in spectral elements. I've read in documentation that i,j,k,e in xm1(i,j,k,e), for example, are changed from 1 to nx1,ny1,nz1 and nelv respectively. But during my tests it's seemed that in different elements x,y,z axis not always correspond to the global coordinate system. Am I right? And how could I change only the lowest slice of an element, for example? Best regards, Elizabeth

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