From nek5000-users at lists.mcs.anl.gov Tue Dec 4 06:20:58 2018 From: nek5000-users at lists.mcs.anl.gov (nek5000-users at lists.mcs.anl.gov) Date: Tue, 04 Dec 2018 15:20:58 +0300 Subject: [Nek5000-users] =?utf-8?q?Problem_with_the_number_of_itterations?= Message-ID: 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 ? -------------- next part -------------- An HTML attachment was scrubbed... URL: From nek5000-users at lists.mcs.anl.gov Tue Dec 4 06:54:00 2018 From: nek5000-users at lists.mcs.anl.gov (nek5000-users at lists.mcs.anl.gov) Date: Tue, 4 Dec 2018 06:54:00 -0600 Subject: [Nek5000-users] Problem with the number of itterations In-Reply-To: References: Message-ID: 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 at 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 at lists.mcs.anl.gov > https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users > -------------- next part -------------- An HTML attachment was scrubbed... URL: From nek5000-users at lists.mcs.anl.gov Wed Dec 5 00:33:44 2018 From: nek5000-users at lists.mcs.anl.gov (nek5000-users at lists.mcs.anl.gov) Date: Wed, 05 Dec 2018 09:33:44 +0300 Subject: [Nek5000-users] =?utf-8?q?Problem_with_the_number_of_iterations?= Message-ID: 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? >???????, 4 ??????? 2018, 19:56 +07:00 ?? nek5000-users--- via Nek5000-users : > > >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 at 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 at lists.mcs.anl.gov >>https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users >_______________________________________________ >Nek5000-users mailing list >Nek5000-users at lists.mcs.anl.gov >https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users >? -------------- next part -------------- An HTML attachment was scrubbed... URL: From nek5000-users at lists.mcs.anl.gov Wed Dec 5 06:42:38 2018 From: nek5000-users at lists.mcs.anl.gov (nek5000-users at lists.mcs.anl.gov) Date: Wed, 5 Dec 2018 06:42:38 -0600 Subject: [Nek5000-users] Problem with the number of iterations In-Reply-To: References: Message-ID: You can try setting the divergence and helmholtz tolerances to zero in the .rea file. Then nek will automatically estimate reasonable tolerances based on the settings that you currently have for tolrel. Given that your inflow and chord are not 1, this might be a good idea. There is nothing intrinsically wrong with an iteration count of 1, however. Paul On Wed, Dec 5, 2018 at 12:34 AM nek5000-users--- via Nek5000-users < nek5000-users at lists.mcs.anl.gov> wrote: > 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? > > > ???????, 4 ??????? 2018, 19:56 +07:00 ?? nek5000-users--- via > Nek5000-users : > > > 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 at 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 at lists.mcs.anl.gov > > https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users > > _______________________________________________ > Nek5000-users mailing list > Nek5000-users at lists.mcs.anl.gov > > https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users > > > _______________________________________________ > Nek5000-users mailing list > Nek5000-users at lists.mcs.anl.gov > https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users > -------------- next part -------------- An HTML attachment was scrubbed... URL: From nek5000-users at lists.mcs.anl.gov Tue Dec 4 11:56:47 2018 From: nek5000-users at lists.mcs.anl.gov (nek5000-users at lists.mcs.anl.gov) Date: Tue, 04 Dec 2018 20:56:47 +0300 Subject: [Nek5000-users] =?utf-8?q?Problem_with_the_number_of_itterations?= In-Reply-To: References: Message-ID: 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? >???????, 4 ??????? 2018, 19:55 +07:00 ?? nek5000-users--- via Nek5000-users : > > >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 at 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 at lists.mcs.anl.gov >>https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users >_______________________________________________ >Nek5000-users mailing list >Nek5000-users at lists.mcs.anl.gov >https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users -------------- next part -------------- An HTML attachment was scrubbed... URL: From nek5000-users at lists.mcs.anl.gov Wed Dec 5 00:24:29 2018 From: nek5000-users at lists.mcs.anl.gov (nek5000-users at lists.mcs.anl.gov) Date: Wed, 05 Dec 2018 09:24:29 +0300 Subject: [Nek5000-users] =?utf-8?q?Problem_with_the_number_of_itterations?= In-Reply-To: References: Message-ID: 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? >???????, 4 ??????? 2018, 19:55 +07:00 ?? nek5000-users--- via Nek5000-users : > > >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 at 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 at lists.mcs.anl.gov >>https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users >_______________________________________________ >Nek5000-users mailing list >Nek5000-users at lists.mcs.anl.gov >https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users -------------- next part -------------- An HTML attachment was scrubbed... URL: From nek5000-users at lists.mcs.anl.gov Wed Dec 5 09:59:29 2018 From: nek5000-users at lists.mcs.anl.gov (nek5000-users at lists.mcs.anl.gov) Date: Wed, 5 Dec 2018 15:59:29 +0000 Subject: [Nek5000-users] Solving the Poisson equation in Nek5000 Message-ID: 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 -------------- next part -------------- An HTML attachment was scrubbed... URL: From nek5000-users at lists.mcs.anl.gov Thu Dec 6 19:03:05 2018 From: nek5000-users at lists.mcs.anl.gov (nek5000-users at lists.mcs.anl.gov) Date: Thu, 6 Dec 2018 19:03:05 -0600 Subject: [Nek5000-users] Solving the Poisson equation in Nek5000 In-Reply-To: References: Message-ID: Dear Zhe, You can solved the steady conduction (heat transfer problem). So, you would just run heat, no fluid.. Paul Fischer On Thu, Dec 6, 2018 at 7:00 PM nek5000-users--- via Nek5000-users < nek5000-users at lists.mcs.anl.gov> wrote: > 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 > _______________________________________________ > Nek5000-users mailing list > Nek5000-users at lists.mcs.anl.gov > https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users > -------------- next part -------------- An HTML attachment was scrubbed... URL: From nek5000-users at lists.mcs.anl.gov Thu Dec 6 23:46:31 2018 From: nek5000-users at lists.mcs.anl.gov (nek5000-users at lists.mcs.anl.gov) Date: Fri, 7 Dec 2018 05:46:31 +0000 Subject: [Nek5000-users] Solving the Poisson equation in Nek5000 In-Reply-To: References: Message-ID: Dear Paul, Thanks so much for your kind reply. Actually I have tried this approach before, where I used the passive scalar solver. The PS solver requires two parameters, namely the ?density? and ?diffusivity?, then I set the ?density? to zero and ?diffusivity? to one, finally only the diffusive term and source term would be remained in the equation for this scalar, which seems very like a Poisson equation. But in my case, I really need to solve such a Poisson-like equation in the ?userchk? subroutine during to the synchronization problem. From the former archive of mailing list in Nek5000, I noticed that some people have used the subroutine ?hmholtz? to obtain the stream function from vorticity. This subroutine has the following form ?hmholtz(?psi?, psi, rhs, h1, h2, tmask, tmult, imsh, tol, 200, 1)?, I understand that this solver need iteration to obtain ?psi?, but I am confused about some other input parameters. 1. The first one is about ?rhs?. I heard it must be multiplied by the ?bm1?. For example, I want to solve ?\nabla^2 psi = 1?, so I must set ?call rone(rhs, n)? and ?call col2(rhs, bm1, n)?, right? 2. The second is about ?psi?. In my case, this ?psi? has its own boundary conditions, including both Dirichlet and Neumann. To achieve this goal, I created an extra mesh for ?psi? in the box file, namely t(1,1,1,1,1) denoting ?psi?, so the boundary conditions can be included. In my understanding, ?tmask(1,1,1,1,ifield-1)? denotes the boundary information for T-mesh ?ifield-1?. 3. The third one is about ?tmult?. What is the function of this parameter? Thanks very much for your time. Best regards, Zhe From: Nek5000-users On Behalf Of nek5000-users--- via Nek5000-users Sent: Friday, 7 December 2018 9:03 AM To: nek5000-users at lists.mcs.anl.gov Subject: Re: [Nek5000-users] Solving the Poisson equation in Nek5000 Dear Zhe, You can solved the steady conduction (heat transfer problem). So, you would just run heat, no fluid.. Paul Fischer On Thu, Dec 6, 2018 at 7:00 PM nek5000-users--- via Nek5000-users > wrote: 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 _______________________________________________ Nek5000-users mailing list Nek5000-users at lists.mcs.anl.gov https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users -------------- next part -------------- An HTML attachment was scrubbed... URL: From nek5000-users at lists.mcs.anl.gov Sat Dec 15 19:44:58 2018 From: nek5000-users at lists.mcs.anl.gov (nek5000-users at lists.mcs.anl.gov) Date: Sun, 16 Dec 2018 09:44:58 +0800 (CST) Subject: [Nek5000-users] Error Hmholtz VELZ Message-ID: 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 -- ??? ?????? ???? ??????? ??????????28? ???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 at 163.com -------------- next part -------------- An HTML attachment was scrubbed... URL: From nek5000-users at lists.mcs.anl.gov Wed Dec 19 04:36:10 2018 From: nek5000-users at lists.mcs.anl.gov (nek5000-users at lists.mcs.anl.gov) Date: Wed, 19 Dec 2018 11:36:10 +0100 Subject: [Nek5000-users] New User Forum - Switch Today Message-ID: 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 at googlegroups.com to post a new topic. Cheers, Stefan From nek5000-users at lists.mcs.anl.gov Wed Dec 19 10:44:08 2018 From: nek5000-users at lists.mcs.anl.gov (nek5000-users at lists.mcs.anl.gov) Date: Wed, 19 Dec 2018 17:44:08 +0100 Subject: [Nek5000-users] Test Message-ID: Test Sent from my iPhone From nek5000-users at lists.mcs.anl.gov Wed Dec 19 10:47:33 2018 From: nek5000-users at lists.mcs.anl.gov (nek5000-users at lists.mcs.anl.gov) Date: Wed, 19 Dec 2018 17:47:33 +0100 Subject: [Nek5000-users] Test 2 Message-ID: Test Sent from my iPhone From nek5000-users at lists.mcs.anl.gov Wed Dec 19 10:49:15 2018 From: nek5000-users at lists.mcs.anl.gov (nek5000-users at lists.mcs.anl.gov) Date: Wed, 19 Dec 2018 17:49:15 +0100 Subject: [Nek5000-users] Test 3 Message-ID: Test 3 Sent from my iPhone From nek5000-users at lists.mcs.anl.gov Wed Dec 19 11:02:59 2018 From: nek5000-users at lists.mcs.anl.gov (nek5000-users at lists.mcs.anl.gov) Date: Wed, 19 Dec 2018 18:02:59 +0100 Subject: [Nek5000-users] test4 Message-ID: From nek5000-users at lists.mcs.anl.gov Wed Dec 19 11:12:19 2018 From: nek5000-users at lists.mcs.anl.gov (nek5000-users at lists.mcs.anl.gov) Date: Wed, 19 Dec 2018 18:12:19 +0100 Subject: [Nek5000-users] Test5 Message-ID: Sent from my iPhone From nek5000-users at lists.mcs.anl.gov Wed Dec 26 23:31:15 2018 From: nek5000-users at lists.mcs.anl.gov (nek5000-users at lists.mcs.anl.gov) Date: Thu, 27 Dec 2018 05:31:15 +0000 Subject: [Nek5000-users] Define Object Message-ID: 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. -------------- next part -------------- An HTML attachment was scrubbed... URL: