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

Further to the issue of ffx, ffy and ffz
by nek5000-users＠lists.mcs.anl.gov 26 Feb '18

26 Feb '18

Hi, May I push the following question further? Is there anyone know what are the exact meaning for para(54) and (55) in rea file? Such as, what's the difference between: 0,0 and -3 1 for (54) and (55) respectively? what's meaning for sign (+) or (-)? Kind regards, Zhai Hi Philipp, Yes, they are shear velocity and bulk velocity. Can I say if the ffx, ffy or ffz equal to (u_t/u_b)^2, the flow is specified as a fixed pressure gradient in the channel, and parameter(54) and para(55) in rea file are fixed as 0. Otherwise, if the all ffx, ffy and ffz are 0, the flow is fixed at flow rate rather than pressure gradient? Cheers, Zhai

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Mismatch of X,Y cordinates
by nek5000-users＠lists.mcs.anl.gov 26 Feb '18

26 Feb '18

Hi Neks, I was trying to make sure the the moving wall condition has properly applied on .rea file by writing the x and y co -ordinates through the .usr file during the run time to a file called rectangle.dat (element number,face number,x,y respectively). But it looks bit different from what i have i given in .rea file. Esepacially if you check the output data file called rectangle.dat on line 5, the x and y co ordinates are 0.9375,0.9375 corresponding to the 133rd element and 2nd phase. But if we check the .rea file its not showing the right one. I have attached all the necessary files to run this case and could you please tell me what went wrong? Thanks in advance

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Dissipation rate
by nek5000-users＠lists.mcs.anl.gov 25 Feb '18

25 Feb '18

Hi, Nek users. I am trying to calculate the dissaipation rate now. In my subroutine which computes the derivatives I use following procedure for smoothing: call col2 ( dui_dxj, bm1, ntot ) call dssum( dui_dxj, lx1, ly1, lz1 ) call col2 ( dui_dxj, binvm1, ntot ) and there are some unrealistic values on the surface between spectral elements. I set up also additional filtering of high modes of velocity with various transfer functions, but it did not help. Do you have any idea about the causes and how to fixed this ? Regards, Vatslav

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turbChannel: Polynomial order
by nek5000-users＠lists.mcs.anl.gov 25 Feb '18

25 Feb '18

Dear Nek users, I am aware of that the mesh resolution is related to the polynomial order. In the turbChannel, P-order is 8, which makes 8 grid for each element in the domain. I am wondering could I change (decrease or increase) this order just for one direction? Let's say in the spanwise direction (z), I only need P-order to be 6 while the other two directions to be 8. Could I do this? Thanks for your help! Regards, Emily

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Blasius example
by nek5000-users＠lists.mcs.anl.gov 24 Feb '18

24 Feb '18

Dear Nek users, I am new to the Nek5000 and have a few quick questions. I noticed that in the SIZE file of Blasius, the number of specified elements does not really match the actual number in the .rea file. I tried to re-generate the .rea file, but I do not have .box file or any other file I could use to modify the specifications in the Blasius folder. So could anyone tell me where could I find the corresponding .box file for this case? And there is a .sep file in the folder, is anyone aware of what is it for? Regards, Ming

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Tripping mechanism
by nek5000-users＠lists.mcs.anl.gov 23 Feb '18

23 Feb '18

Dear all, I've seen several papers using Nek5000 with a tripping mechanism based on a forcing term, explained in a paper by Schlatter & Örlü (2012). However, they talk about using random harmonic signals h^{i}(z). My question is: What is the shape of such signals and how do you make them random? Thanks, Juan Diego

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Help
by nek5000-users＠lists.mcs.anl.gov 23 Feb '18

23 Feb '18

> On Feb 23, 2018, at 12:00 PM, "nek5000-users-request(a)lists.mcs.anl.gov" <nek5000-users-request(a)lists.mcs.anl.gov> wrote: > > Send Nek5000-users mailing list submissions to > nek5000-users(a)lists.mcs.anl.gov > > To subscribe or unsubscribe via the World Wide Web, visit > https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flists.mcs.… > or, via email, send a message with subject or body 'help' to > nek5000-users-request(a)lists.mcs.anl.gov > > You can reach the person managing the list at > nek5000-users-owner(a)lists.mcs.anl.gov > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of Nek5000-users digest..." > > > Today's Topics: > > 1. Tripping mechanism (nek5000-users(a)lists.mcs.anl.gov) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Fri, 23 Feb 2018 17:29:43 +0000 > From: nek5000-users(a)lists.mcs.anl.gov > To: "nek5000-users(a)lists.mcs.anl.gov" > <nek5000-users(a)lists.mcs.anl.gov> > Subject: [Nek5000-users] Tripping mechanism > Message-ID: > <mailman.9387.1519406985.19102.nek5000-users(a)lists.mcs.anl.gov> > Content-Type: text/plain; charset="iso-8859-1" > > Dear all, > > > I've seen several papers using Nek5000 with a tripping mechanism based on a forcing term, explained in a paper by Schlatter & ?rl? (2012). However, they talk about using random harmonic signals h^{i}(z). My question is: What is the shape of such signals and how do you make them random? > > > Thanks, > > > Juan Diego >

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Re: [Nek5000-users] Instantaneous velocity field
by nek5000-users＠lists.mcs.anl.gov 21 Feb '18

21 Feb '18

Hello, Thank you for the reply. I am aware of those lines are intended for time-averaging. I was wondering if anyone could teach me how to generate the instantaneous velocity field in a similar pattern like the following: open(unit=56,file='vel_fluc_prof.dat') write(56,'(A,1pe14.7)') '#time = ', time write(56,'(A)') & '# y y+ uu vv ww uv' Thanks a lot, Tim ________________________________ this is not really instantaneous data, but rather statistics. Then you would need to run some kind of averaging (in time, space etc.) and proper postprocessing afterwards, which strongly depends on the actual flow case. I am sure that there are people in this group that have done this type of analysis for a variety of flow cases/geometries.

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Re: [Nek5000-users] Instantaneous velocity field
by nek5000-users＠lists.mcs.anl.gov 21 Feb '18

21 Feb '18

Hello, Thank you for the reply. Yes, outpost() in fact does yield the information I am looking for. But I hope I could generate the field information in .dat file similar to following pattern: open(unit=56,file='vel_fluc_prof.dat') write(56,'(A,1pe14.7)') '#time = ', time write(56,'(A)') & '# y y+ uu vv ww uv' Could you please teach me how to do this? Regards, Tim ________________________________ I forgot to add 'call' before outpost. Please read the block as: if (istep .eq. 10) then call outpost(vx,vy,vz,pr,t,'vel') endif On 02/21/2018 04:33 PM, Navrose Navrose wrote: > > Doesn't outpost() (userchk subroutine) inside a conditional statement > address your issue? > Something like (if you have to flow information at istep=10): > > if (istep .eq. 10) then > outpost(vx,vy,vz,pr,t,'vel') > endif > > > On 02/21/2018 04:22 PM, nek5000-users at lists.mcs.anl.gov<https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users> wrote: >> >> Hello, >> >> Thank you for the reply. I meant the instantaneous velocity field for >> the domain (u(x,y,z),v(x,y,z),w(x,y,z)) at some certain time step >> (istep). >> >> Regards, >> >> Tim

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Re: [Nek5000-users] Instantaneous velocity field
by nek5000-users＠lists.mcs.anl.gov 21 Feb '18

21 Feb '18

I forgot to add 'call' before outpost. Please read the block as: if (istep .eq. 10) then call outpost(vx,vy,vz,pr,t,'vel') endif On 02/21/2018 04:33 PM, Navrose Navrose wrote: > > Doesn't outpost() (userchk subroutine) inside a conditional statement > address your issue? > Something like (if you have to flow information at istep=10): > > if (istep .eq. 10) then > outpost(vx,vy,vz,pr,t,'vel') > endif > > > On 02/21/2018 04:22 PM, nek5000-users(a)lists.mcs.anl.gov wrote: >> >> Hello, >> >> Thank you for the reply. I meant the instantaneous velocity field for >> the domain (u(x,y,z),v(x,y,z),w(x,y,z)) at some certain time step >> (istep). >> >> Regards, >> >> Tim >> >> ------------------------------------------------------------------------ >> >> do you mean how to write out an instantaneous field, or to generate an >> initial condition? >> On 2018-02-21 11:55, nek5000-users at lists.mcs.anl.gov >> <https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users> wrote: >> >/The subroutine useric (in the usr file) is used to specify the initial / >> >/condition for the whole domain./ >> >// >> >/On 21 Feb 2018, at 05:41, "nek5000-users at lists.mcs.anl.gov >> <https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users> / >> >/<mailto:nek5000-users at lists.mcs.anl.gov >> <https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users>>" / >> >/<nek5000-users at lists.mcs.anl.gov >> <https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users> / >> >/<mailto:nek5000-users at lists.mcs.anl.gov >> <https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users>>> wrote:/ >> >// >> >>/Dear Nek users,/ >> >>// >> >>/Could anyone please teach me how to generate an instantaneous velocity / >> >>/field for the whole domain (letï¿½s say for just one time step and have / >> >>/it stored in a .dat file) for case of turbChannel. I have been / >> >>/tracking/reading many subroutines and files, but I could not find the / >> >>/location where I could add lines to generate the instantaneous / >> >>/velocity profile./ >> >>// >> >>/Thank you./ >> >>// >> >>/Tim/ >> >> >> >> _______________________________________________ >> Nek5000-users mailing list >> Nek5000-users(a)lists.mcs.anl.gov >> https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users >

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