- Nektar-users - imperial.ac.uk

PressureOutflow boundary condtions
by 中华腾飞 19 Dec '18

19 Dec '18

Hi all! I want to give static pressure on my outlet, p0eInf is the value that i have defined in parameters . Can you help me check out my example? By the way, i don't know how to set 'WallAdiabatic' boundary conditions ,can you help me check out my example? Sometimes when i run the calculation,it will report an error called 'vacuum is generated by given data'.If i change the TimeStep , it will calculate some steps.How to explain it? Looking forward to your replay!

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nektar++ mesh
by 中华腾飞 18 Dec '18

18 Dec '18

Hi all! When i calculate my task , there is always an error called 'vacuum is generated by given data' .I have tried to check out my boundary conditions and initial conditions ,but it doesn't work. I want to check out my meshes .My meshes are generated by gmsh 3.0.6, all the elements are 'A' (tetrahedron) and about 36912. Can you give me some suggestions about my meshes or geometry?Looking forward to your reply!

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help my condition.xml
by 中华腾飞 18 Dec '18

18 Dec '18

Hi all! I will give you about my condition.xml ,I hope someone can help me to refine it. In parameters list, p0,rho0Inf,u0Inf,v0Inf,w0Inf are parameters on the first inlet called ' REF="0" ',pc,rhocInf,ucInf,vcInf wcInf are parameters on the second inlet ' REF="2" '.They are all static values. p0e is the static pressure on the first outlet called " REF="1" ' , pce is the static pressure on the second outlet called " REF="3" '. I want to use 'PressureOutlet' boundary condtions ,how to write the condtions? On the REF="4" ,i want to use the 'WallAdiabatic',how to write it? Hope you can write your answer in my condition.xml ,i will learn it as a reference! Looking forward to your reply!

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compressible flow solver
by 中华腾飞 17 Dec '18

17 Dec '18

Hi all! Can you give me an specific example in using 'PressureOutflow' and 'WallAdiabatic' boundary conditions? On the website i don't know why the values are set to zeros...

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compressible solver issues
by 中华腾飞 17 Dec '18

17 Dec '18

Hi all! I want to ask about the boundray conditions.In 3D task,the variables are only rho,rhou,rhov,rhow and E? We can't set other variables,such as p(pressure),t(temperature)? In D type boundary condtions,if i give values to variables,such as ' VAR="rho" VALUE="rhoInf" after i have defined rhoInf=1.007, it means rho=1.007? In some tutorials, they set VALUE="0",rho=0 or E=0,it seems to be impossible!

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problems in using compressible flow solver
by 中华腾飞 16 Dec '18

16 Dec '18

Hi all! I have met some problems in using compressible flow solver. When i begin to calculate ,after some steps ,it will stop and print an error on the screen called'vacuum is generated by given data'. Now, i will talk about my task. If you open the fight.geo with gmsh 3.0.6,you will see a box. You can also open the fight.msh file with gmsh which you can see the generated meshes .Inlet is on the left and outlet is on the right. I want to give total values like total temperature and total pressure on the inlet (T*=1600K,P*=1312800Pa,Ma=0.33),but when i see the tutorials about compressible flow solver,it seems that i should give values like rhoInf ,rhoInf*uInf and so on,i don't know whether my understanding is right or not .I have to calculate static values through total values and i do that .You can see my fight.xml file,the REF=0 is the boundary of inlet,and values use the parameters defined before.Then i want to give static pressure on the outlet, on the REF=1, i use the 'pressureoutflow' condition,because of no examples of this condition, i don't know how to set right values.... On the REF=2, i want to use 'walladiabatic' condition ,because of no examples of this condtion,i also don't know how to set right values... Initial condition is same to the inlet. I hope you can give me some suggestions. Looking forward to your reply!

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(no subject)
by Xu Chu 14 Dec '18

14 Dec '18

Dear all, Recently I am facing some issues in the post-processing. I use "FieldConvert -m gradient" to get velocity gradient and "FieldConvert -m meanmode" to do spatial averaging in my 3DH1D simulation. They both worked in my previous experiences. However, I found some problem recently. When I am running "-m gradient", I can not convert it to the chk format, but I can convert it directly to vtu format. with chk/fld format, the error shows "Unable to extract the data from the element tag." I am trying to understand it in the source code. But it is still not so clear to me. The other fieldconvert utilities like -vorticity works. When I use "-m meanmode", sometimes it gives me the error "Input data is not the same length as header information". It is also very confusing. Hope someone can help me out here. Merry Christmas and happy new year to all Nektarer. Xu Chu

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BiGlobal Stability Analysis of 3D Channel Flow case at Re15000
by Xu Chu 14 Dec '18

14 Dec '18

Dear Nektarers, I am running a 3D direct stability analysis test case, the Re15000 Channel Flow from the tutorial (PPF_R15000_3D, ARPACK as the solver). As I understand, this is a BiGlobal stability analysis with 2D base flow and the spanwise wavenumber Beta. It means that for a given Beta, the Eigenvalues can be calculated. What I am seeking is the Eigenvalues under different spanwise wavenumber Beta, so I turn "Beta Set To Zero" as false (as in the PPF_R15000_3D). And the solver converged showing 4 Eigenvalues with Real and Imaginary part of each, with no information of Beta. How can I find the Eigenvalues under different spanwise wavenumber Beta? Thank you very much. Best Regards, Xu

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issue in my calculation
by 中华腾飞 11 Dec '18

11 Dec '18

Thank you for reading my letter with your busy schedule. I'm an undergraduate so i'm not so skilled in CFD. Now i have a task that need me to use nektar++,but when i use the compressible solver to calculate it , the error 'vacuum is generated by given data' always comes up. I try to change my boundry conditions,but it doesn't work. Can you give me some suggestions? Looking forward to your reply!

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Re: [Nektar-users] Handling Pyramids
by Vishal Saini 07 Dec '18

07 Dec '18

Dear Spencer and David, Thanks very much for your prompt replies. 1. Defining the expansions separately still produced the "note" (in Nektar 4.4.1 Release). 2. Compiling the latest master solved the problem. However, I didn't try if defining the expansions collectively i.e. *<E COMPOSITE="C[1,10,11]" NUMMODES="3" FIELDS="u,v,w,p" TYPE="MODIFIED" /> *produces any warnings in the latest compilation. BR, Vishal --- *Vishal SAINI* On Mon, Nov 26, 2018 at 4:43 PM Moxey, David <D.Moxey(a)exeter.ac.uk> wrote: > Hi Vishal, > > You might also try a newer version of the code (i.e. latest master), I am > not sure that the pyramid collections functions were added in 4.4.1. > > Many thanks, > > Dave > > > On 26 Nov 2018, at 14:53, Sherwin, Spencer J <s.sherwin(a)imperial.ac.uk> > wrote: > > > > Dear Vishal, > > > > I do not quite recall but it may be necessary to define the expansions > for composites of different shape independently. So please try: > > > >> <E COMPOSITE=“C[1]" NUMMODES="3" FIELDS="u,v,w,p" TYPE="MODIFIED" /> > >> <E COMPOSITE=“C[10]" NUMMODES="3" FIELDS="u,v,w,p" TYPE="MODIFIED" /> > >> <E COMPOSITE="C[11]" NUMMODES="3" FIELDS="u,v,w,p" TYPE="MODIFIED" /> > > > > Possibly it is expecting to have a pyramid collection within a > tetrahedral expansion and so this is why you see this message. > > > > If this does not work can you send the xml file along. > > > > Thanks, > > Spencer. > > > > > >> On 26 Nov 2018, at 11:45, Vishal Saini <vishal.saini.nitj(a)gmail.com> > wrote: > >> > >> Hi all, > >> > >> I've imported a mesh from gmsh that contains a layer of pyramids for > transitioning between hexes and tets using: > >> NekMesh JICF_NektP2_2comp.msh JICF_NektP2_2comp.xml > >> Output: > >> Multiple elements in composite detected; remapped: > >> - Tag 1 => 11 (Tetrahedron), 10 (Pyramid), 1 (Hexahedron) > >> No problem on NekMesh level. > >> > >> Defining my expansion as: > >> <E COMPOSITE="C[1,10,11]" NUMMODES="3" FIELDS="u,v,w,p" TYPE="MODIFIED" > /> > >> > >> when I run (Nektar++ v 4.4.1) using: > >> mpirun -npernode 28 -np 56 IncNavierStokesSolver -v > JICF_NektP2_2comp_xml conditions_JICF_2D.xml > >> (using prepartitioned mesh). > >> I get the following "note": > >> Collection Implemenation for Tetrahedron ( 3 3 3 ) for ngeoms = 24960 > >> Note: Implementation does not exist: Pyramid, BwdTrans, SumFac, Modal > >> Note: Implementation does not exist: Pyramid, IProductWRTBase, SumFac, > Modal > >> Note: Implementation does not exist: Pyramid, IProductWRTDerivBase, > SumFac, Modal > >> Note: Implementation does not exist: Pyramid, PhysDeriv, SumFac, Modal > >> Note: Implementation does not exist: Pyramid, BwdTrans, SumFac, Modal > >> Note: Implementation does not exist: Pyramid, IProductWRTBase, SumFac, > Modal > >> Note: Implementation does not exist: Pyramid, IProductWRTDerivBase, > SumFac, Modal > >> Note: Implementation does not exist: Pyramid, PhysDeriv, SumFac, Modal > >> > >> What does it mean? How can I fix it? > >> Do Pyramids need to be treated in a somewhat different way? > >> > >> BR, > >> Vishal > >> > >> > >> --- > >> Vishal SAINI > >> _______________________________________________ > >> Nektar-users mailing list > >> Nektar-users(a)imperial.ac.uk > >> https://mailman.ic.ac.uk/mailman/listinfo/nektar-users > > > > Spencer Sherwin FREng, FRAeS > > Head, Aerodynamics, > > Director of Research Computing Service, > > Professor of Computational Fluid Mechanics, > > Department of Aeronautics, > > s.sherwin(a)imperial.ac.uk South > Kensington Campus, > > Phone: +44 (0)20 7594 5052 Imperial College > London, > > Fax: +44 (0)20 7594 1974 London, SW7 > 2AZ, UK > > http://www.imperial.ac.uk/people/s.sherwin/ > > > > _______________________________________________ > > Nektar-users mailing list > > Nektar-users(a)imperial.ac.uk > > https://mailman.ic.ac.uk/mailman/listinfo/nektar-users > >

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