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

Problems in getting eigenvalues using ARNOLDI
by nek5000-users＠lists.mcs.anl.gov 08 Nov '18

08 Nov '18

Hi Nek, I am running ARNOLDI simulation case for a flow over a 2D cylinder using ARPACK . My domain is [-50,50] and Re=50. I have calculated base flow using SFD method. While calculating Eigen values I have to run the restart around 16-20 times to get an eigenvalues.txt file as an output. Also the eigenvalues that are coming most of them has zero rotation i.e., they are negative real value. Suppose I want to have 30 eigenvalues as an output and I am setting Krylov subspace as 90 then I am getting around 20 of eigenvalues having zero rotation. Kindly help as I am stuck in it for long. Thanks in advance. Regards, Alok Mishra Aerospace Department IIT Kanpur

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Rotating computational domain
by nek5000-users＠lists.mcs.anl.gov 13 Oct '18

13 Oct '18

Hello Neks, I am an undergraduate student new to Nek and I am working on a simulation studying dynamic stall in a dynamically pitching airfoil. I want to do a pitch and hold simulation at low Reynold's number (Re = 12000) where I rotate the entire computational domain up to about 50 degrees AOA and then hold at 50 degrees, with steady inflow ux = 1. I would like to rotate the domain about the z axis, which passes through the quarter chord location of the airfoil profile (modified NACA 0012). Because of the steep AOA, I would like to stay away from pitching the airfoil within the stationary domain with ALE to avoid too much mesh deformation. To this end, I have been scouring documentation to try and find a method of applying a rotational mesh velocity to the entire domain about the z axis while keeping the flow within the domain at ux = 1. I am feeling very stuck. Others have suggested applying a Coriolis force to the flow, but I don't really see how this would simulate rotation of the entire domain. It seems to me that simulation of a Coriolis force would be acceptable to correct the flow field to always be ux = 1 inside a rotating domain, but I don't see how that would apply a mesh velocity anywhere. Are there any examples where an entire computational domain is rotated that I can look at, or has anybody done similar work who can point me in the right direction? Regards, -Harry

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Nekbone correctness
by nek5000-users＠lists.mcs.anl.gov 28 Sep '18

28 Sep '18

Dear Neks, I was wondering if someone could help us to identify correctness tests for Nekbone. How can we make sure that after modifying the code we still get a valid output? Is there anything we can use from the printed output, for instance |/cg: ||0| |3||.9174E+||02| /|/comm time ||0||.2370E-||01| /|/cg: ||101| |2||.9280E-||05| |4||.3327E-||01| |7||.6135E-||01| /|/2||.5748E-||09| /|/cg: ||0| |4||.0900E+||02| /|/comm time ||0||.2232E-||01| /|/cg: ||101| |1||.0800E-||05| |4||.4507E-||01| |7||.4233E-||01| /|/3||.4828E-||10| /|/| /|/nelt = ||64||, np = ||8||, nx1 = ||10||, elements /= ||512| |/Tot MFlops = ||4||.0983E+||04||, MFlops = ||5||.1228E+||03| /|/Setup Flop = ||8||.8960E+||08||, Solver Flop = ||9||.6960E+||07| /|/Solve Time = ||0||.1926E+||00| /|/Avg MFlops = ||4||.0983E+||04| / Thanks for your help! The University of Edinburgh is a charitable body, registered in Scotland, with registration number SC005336.

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Merging two meshes.
by nek5000-users＠lists.mcs.anl.gov 27 Sep '18

27 Sep '18

Hello Everyone, I am a brand new user to NEK5000. I want to merge a circular mesh with a box mesh. Can someone guide me how to do this. Regards, Rohan.

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Re: [Nek5000-users] info
by nek5000-users＠lists.mcs.anl.gov 26 Sep '18

26 Sep '18

To install the GNU C/Fortran compilers + MPI, just run brew install gcc brew install gfortran brew install open-mpi To compile and run Nek5000 just follow the instructions outlined in: http://nek5000.github.io/NekDoc/quickstart.html#running-your-very-first-sim… -----Original message----- > From:[email protected] <nek5000-users(a)lists.mcs.anl.gov> > Sent: Wednesday 26th September 2018 22:26 > To: nek5000-users(a)lists.mcs.anl.gov > Subject: Re: [Nek5000-users] info > > No I haven't installed the software below but I will do. I have tried to install it using the terminal but unsuccessfully, I do not have a great knowledge of it, I have tried with Homebrew.On-line I found a sequence of instructions about installation on ubuntu. Something like that would be really useful. > Thank you for your replies. > Kind Regards > > Federico > > > > > On 26 Sep 2018, at 17:44, "nek5000-users(a)lists.mcs.anl.gov" <nek5000-users(a)lists.mcs.anl.gov> wrote: > > > > Can you please be more specific. How do the "difficulties" manifest itself? > > > > -----Original message----- > >> From:[email protected] <nek5000-users(a)lists.mcs.anl.gov> > >> Sent: Wednesday 26th September 2018 18:39 > >> To: nek5000-users(a)lists.mcs.anl.gov > >> Subject: [Nek5000-users] info > >> > >> Hi, > >> I am having difficulties with installing the software on a Mac. > >> I would like to know if somebody can provide some help please. > >> I have read the documents already. > >> Thank you. > >> > >> Federico > >> > >> _______________________________________________ > >> 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 > _______________________________________________ > Nek5000-users mailing list > Nek5000-users(a)lists.mcs.anl.gov > https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users >

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info
by nek5000-users＠lists.mcs.anl.gov 26 Sep '18

26 Sep '18

Hi, I am having difficulties with installing the software on a Mac. I would like to know if somebody can provide some help please. I have read the documents already. Thank you. Federico

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Question about tolerance
by nek5000-users＠lists.mcs.anl.gov 26 Sep '18

26 Sep '18

Hi, Neks! I'm wonder why in .par file, for example in the turbChannel case, there are different tolerances for pressure and for velocity? I mean that velocity seems to be dependent on pressure field, and if it is 10^-4 tolerance for the pressure, it will automatically the same for the velocity? Best regards, Vlad

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invalid handle in findpts
by nek5000-users＠lists.mcs.anl.gov 24 Sep '18

24 Sep '18

Hi nek, When findpts was called, the error happened when interpolated points are 90000, as shown below. But it is fine for interpolation of 10 points as tested. I tried different memory located as maximum as 768GB of memory which is still not working. Can anyone give some suggestion? /nek5_svn/trunk/nek/jl/findpts.c:319): findpts_eval: invalid handle

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interpolation of solution on extra points
by nek5000-users＠lists.mcs.anl.gov 21 Sep '18

21 Sep '18

Hello all, Is it possible to write out the solution from Nek5000 with more points than actually used for calculation? Say, if I ran the simulation with poly. order 7 (i.e. 8 points inside each element per direction), can I write out the solution with 16 sampling points (i.e. solution interpolated on 16 points inside each element per direction)? Thanks for your time. BR Vishal

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Re: [Nek5000-users] rst to ix iy iz
by nek5000-users＠lists.mcs.anl.gov 19 Sep '18

19 Sep '18

Dear Philipp, Thanks for your your suggestion to correct my model which I really appreciate. I want to explain what I am doing and could you please give me some advice. Thanks so much. Now I am doing a Lagrangian particle tracking model with two-way coupling. So the interaction between two phases in my mind, should be added to the Eulerian grid point where the particle is, and the grid point where it belongs to is what I was finding out. I am sorry to say that I don't totally understand the the regularising the force among a number of grid points. I read some IBM papers before. If I were correct, I think the regularised function is employed with interpolating velocity and regularising force among adjacent grid points to keep the interface smooth. Do you think for my piont-particle tracking the regularising is needed? Would you please give me any suggestions? Kind regards, Jian

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