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

Define Object
by nek5000-users＠lists.mcs.anl.gov 26 Dec '18

26 Dec '18

Dear Nek users, I have a couple of questions regarding to defining an irregular object in the channel domain. I plan to set up an irregular object, let’s say a 2D parallelogram, on a flat plate. I have gone through the archives and some examples, and I am thinking of doing this the same way as the example of ‘ext_cyl’ is done: setup the base geometry and mesh for channel, build the geometry and mesh for the object, and lastly merge them with ‘pretex’. I think I have developed some fundamental understanding of ‘prex’ but there are a couple of things I may need some help, which bothered me for a while: 1. How do I properly modify the mesh in prex around this ‘parallelogram’ object after I ‘define object’, such that the mesh around is similar to that in import.rea in ‘ext_cyl’ example? 2. After the definition of object and modification of mesh, how do I ensure this ‘new.rea’ file could be fitted into the base domain? (By the base domain, I am referring to the original channel domain) Would I need to ensure the grid spacing is consistent for both of the .rea files or the ‘new.rea’ could be automatically adjusted after applying ‘Pretex’? I appreciate if someone could give me detailed info, guidance or refer me to some tutorial files. Merry Christmas. Jessica.

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Test5
by nek5000-users＠lists.mcs.anl.gov 19 Dec '18

19 Dec '18

Sent from my iPhone

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test4
by nek5000-users＠lists.mcs.anl.gov 19 Dec '18

19 Dec '18

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Test 3
by nek5000-users＠lists.mcs.anl.gov 19 Dec '18

19 Dec '18

Test 3 Sent from my iPhone

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Test 2
by nek5000-users＠lists.mcs.anl.gov 19 Dec '18

19 Dec '18

Test Sent from my iPhone

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Test
by nek5000-users＠lists.mcs.anl.gov 19 Dec '18

19 Dec '18

Test Sent from my iPhone

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New User Forum - Switch Today
by nek5000-users＠lists.mcs.anl.gov 19 Dec '18

19 Dec '18

Dear Members, this mailing list will be retired soon. Please sign up https://groups.google.com/forum/#!forum/nek5000/join for our new user forum available at https://groups.google.com/forum/#!forum/nek5000 Instead of using the webpage you can email to nek5000(a)googlegroups.com to post a new topic. Cheers, Stefan

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Error Hmholtz VELZ
by nek5000-users＠lists.mcs.anl.gov 15 Dec '18

15 Dec '18

Dear Neks expert, I have met one question regarding convergence process. I have set 20 elements along the flow direction (z direction) within 18 dimensionless length and Errors in Hmholtz VELZ always occur as showing below in some steps. Step 6568, t= 1.1221628E+02, DT= 4.1878394E-03, C= 2.974 1.4417E+05 1.6334E+01 Solving for fluid 6568 Project PRES 5.1352E-02 3.3155E-01 6.4564E+00 13 13 6568 PRES gmres 332 9.9894E-05 1.9371E-03 1.0000E-04 1.5201E+01 2.0723E+01 F 6568 Hmholtz VELX 91 9.5154E-08 1.0497E+00 1.0000E-07 6568 Hmholtz VELY 92 9.6725E-08 1.0499E+00 1.0000E-07 6568 Hmholtz VELZ 94 9.2542E-08 1.3732E+00 1.0000E-07 6568 PRES gmres 1 5.5415E-15 7.3896E-15 1.0000E-04 4.4999E-02 6.6809E-02 F 6568 Hmholtz VELX 1 5.1837E-16 1.2080E-15 1.0000E-07 6568 Hmholtz VELY 1 5.1303E-16 1.2067E-15 1.0000E-07 6568 Error Hmholtz VELZ 100 6.5337E-07 9.9994E-01 1.0000E-07 6568 volflow Z 1.4895E-02 1.3403E-03 3.9043E+01 3.9044E+01 L1/L2 DIV(V) 1.6323E-16 9.7802E-02 L1/L2 QTL 0.0000E+00 0.0000E+00 L1/L2 DIV(V)-QTL 1.6323E-16 9.7802E-02 6568 Fluid done 1.1222E+02 2.5913E+01 dump history points 1.1222E+02 1.0000E+00 1.1906E-02 monitor Could you please lead me the way to avoid this problem? Should I refine the mesh in z direction according to some criteria? Thank you so much for your kindly help. Haoran -- 鞠浩然西安交通大学能动学院核科学与技术系陕西省西安市咸宁西路28号邮编：710049 JU Haoran Department of Nuclear Science and Technology, School of Energy and Power Engineering, Xi'an Jiaotong University, 710049. No.28 Xianning West Road, Xi'an, Shanxi Province, China. Email: juhaoran012(a)163.com

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Solving the Poisson equation in Nek5000
by nek5000-users＠lists.mcs.anl.gov 06 Dec '18

06 Dec '18

Hi all, I am trying to solve an equation similar with the Poisson equation (\nabla^2 \phi = A) in Nek5000, but I do not know which subroutine can do this work properly. The variable \phi in computational domain has Dirichlet boundary conditions (e.g. A = 0). I think maybe the subroutine "hmholtz" can help solve this problem, but I have no idea how to set the commands, including setting of the boundary. Is there anyone having some idea? Any suggestion is welcomed. Thanks for your time. Best regards, Zhe

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Problem with the number of iterations
by nek5000-users＠lists.mcs.anl.gov 05 Dec '18

05 Dec '18

For this geometry, I tried the low Re (~10^3), but the number of iterations for the velx, vely, velz also did not exceed 1. What do you think? Why do I have the same number of iterations for the low Re? >Вторник, 4 декабря 2018, 19:56 +07:00 от nek5000-users--- via Nek5000-users <nek5000-users(a)lists.mcs.anl.gov>: > > >Your problem has very low viscosity, so there will be very few velocity >iterations. > >I would suggest turning off the filter if it's not helping -- but most likely >there is another issue (e.g., perhaps needing more resolution for the target Reynolds >number). > >For a wing, it might not be a bad idea to first run a 2D airfoil at the target conditions >just to get an idea of the meshing requirements for the target Re. > >hth, > >Paul > >On Tue, Dec 4, 2018 at 6:21 AM nek5000-users--- via Nek5000-users < nek5000-users(a)lists.mcs.anl.gov > wrote: >> >>Hi, Neks! >>I am working with a complex geometry which was built in gambit. I have some questions. >>1) When I start Nek5000, I have only 1 itteration for velx, vely,velz, but for the preassure field itterations >30. How can it be possible? >>2) When I set p103=0.1 in .rea file, Courant number increases and becomes >1 very fast. How does the filtration effect on the Courant number? >>I attached my .rea file and logfile. >>https://drive.google.com/open?id=1YEV2f5Mllqenhu-rk39YJ84_1XHYjC_H >> >>https://drive.google.com/open?id=1jRKI_zEnb78cR7uXFi3mE0txk6FN3EXQ >>_______________________________________________ >>Nek5000-users mailing list >>Nek5000-users(a)lists.mcs.anl.gov >>https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users >_______________________________________________ >Nek5000-users mailing list >Nek5000-users(a)lists.mcs.anl.gov >https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users >

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