February 2013 - Nek5000-users - mailman3.cels.anl.gov

turbulent heat transfer
by nek5000-users＠lists.mcs.anl.gov 13 Feb '13

13 Feb '13

Dear all we are trying to make calculations of turbulent heat transfer in a pipe. Everything seems to work fine with the velocity field, however this is not the case for the temperature. It seems as if the convection for the temperature equation is switched off. So, we obtain a turbulent velocity distribution but a laminar temperature distribution. We have tried several thermal boundary condtions and at the moment we are just fixing the temperature at the wall T=0 and adding a heat source qvol=1. In the following we add details of the case. Thanks for your help Regards, Alex rea file ****** PARAMETERS ***** 2.6099999 NEKTON VERSION 3 DIMENSIONAL RUN 103 PARAMETERS FOLLOW 1.00000 p001 DENSITY -750. p002 VISCOS 0.00000 p003 0.00000 p004 0.00000 p005 0.00000 p006 1.00000 p007 RHOCP -0.7 p008 CONDUCT [...] 13 LOGICAL SWITCHES FOLLOW T IFFLOW T IFHEAT T IFTRAN T T F F F F F F F F F IFNAV & IFADVC (convection in P.S. fields) F F T T T T T T T T T T IFTMSH (IF mesh for this field is T mesh) F IFAXIS F IFSTRS F IFSPLIT F IFMGRID F IFMODEL F IFKEPS F IFMVBD F IFCHAR [...] usr file [...] c----------------------------- ------------------------------------------ subroutine userf (ix,iy,iz,ieg) include 'SIZE' include 'TOTAL' include 'NEKUSE' ffx = 0.0 ffy = 0.0 ffz = 2.0 return end c----------------------------------------------------------------------- subroutine userq (ix,iy,iz,ieg) include 'SIZE' include 'TOTAL' include 'NEKUSE' qvol = 1.0 source = 0.0 return end c----------------------------------------------------------------------- [...]

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cyclic boundary conditions and pnpn-2
by nek5000-users＠lists.mcs.anl.gov 13 Feb '13

13 Feb '13

Dear Nek users, I am running both linear and nonlinear simulations of the flow over a rotating disk. To decrease the domain size, I use a circular sector of the disk which is made possible through the cyclic boundary conditions. When I use the cyclic boundary conditions for my nonlinear simulations together with pnpn-2 they blow up. I am not entirely sure why, although, I am currently just using pnpn instead. However, when I use these boundary conditions for my linear simulations, I have to use pnpn-2 since the perturbation solver is only implemented for this specific case, and this seems to work fine. I am also not sure why this works fine whereas the nonlinear case blows up (?). Anyway, my main question is if there are any plans to develop the pnpn-2 case for the cyclic boundary conditions in the nonlinear case? Or maybe what I'm wondering is if this would be an easy task to do? We are experiencing that it is faster to run with pnpn-2 than with pnpn and this would thus be an advantage. Best regards, Ellinor ---------------------------------------------------------------- This message was sent using IMP, the Internet Messaging Program.

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opdiv and multd
by nek5000-users＠lists.mcs.anl.gov 10 Feb '13

10 Feb '13

Hi all, I am having some problems using the subroutines opdiv and multd. For some reasons they do not give me correct results. Do they need any special treatment or precautions? I was trying to compute the divergence of a 3D field, and i realized that in my case the multd subroutine used by opdiv does not gives good results, while the same derivative computed from gram1 gives no problems. For example, I overwrite an analytical field : ... parameter(lt=lx1*ly1*lz1*lelt) real Res(lt) ... vx(i,j,k,e)= 1.0*sin(x)*cos(y)*cos(z) ... call print_line(vx) ... iflg = 1 call multd (RES(1),vx,rym2,sym2,tym2,2,iflg) call print_line(Res(1) ) call gradm1(work1,Res(1),work2,vx) call print_line(Res(1) ) ... if (lx2.ne.lx1) then ... STOP endif and print output a (xr,:,zr) the result (performed by print_line) . In vxi.eps i compare the result (lines) with the analytical solution( symbols). The result of multd is not correct while all the others match perfectly the analytical solution. In vxy.eps i plot only the result of multd. Note that on y i have 12 elements the same number of peaks of the solution. Does anybody have an idea on how to fix this? Thank you very much for any help or suggestion francesco

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Steady Stokes solver
by nek5000-users＠lists.mcs.anl.gov 07 Feb '13

07 Feb '13

Hi Nek's, I was wondering if any one has some exemples on how to set up the steady Stokes solver? Regards, -- Jean-Christophe LOISEAU

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problems in installation
by nek5000-users＠lists.mcs.anl.gov 06 Feb '13

06 Feb '13

Hi, I have just installed Nek5000. I followed the instructions found in the website, but it seems that it doesn't work. Do you have step-by-step instructions? for those who are not expert of linux OS? Many thanks Barak Galanti PS: I am interested in DNS simulations, especially turbulence.

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