- Nektar-users - imperial.ac.uk

Variable or temperature dependent viscosity
by Debbahi Saad 05 Nov '22

05 Nov '22

******************* This email originates from outside Imperial. Do not click on links and attachments unless you recognise the sender. If you trust the sender, add them to your safe senders list https://spam.ic.ac.uk/SpamConsole/Senders.aspx to disable email stamping for this address. ******************* Dear Nektar users, I'm using Nektar++ Incompressible Navier-Stokes Solver in fully 3D mode, with added temperature field, in a plane poiseuille flow heated at the bottom wall, solver running very well, and as if it wasn't already enough, I'm asking for more here ! 'hopefully', --> My question is about the possibility to handle variable viscosity or temperature dependent viscosity, So is there any approach to account for temperature dependent viscosity nu(T) ? I'm asking for this, since the temperature gradient at the heated wall is known to alter the viscosity (Ref: Physics of transitional shear flow, A. V. Boiko et al. Sec. 6.5 page 112) which I have to account for when carrying flow transition calculations. --> In case it is not directly achievable through Nektar's functionalities, is it conceivable to direct my effort toward employing an ad-hoc approach modifying the momentum transfer to account for lower liquid viscosity at higher temperature? That is, most likely adding a forcing term which mimics the effect of varying viscosity by altering the momentum transfer accordingly, since the stress tensor for a newtonian fluid tau=mu.du/dy. Any comment on the sanity of this approach ? Thank you all in advance, any help or general guidelines on this model variation greatly appreciated. Regards, Saad

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About combustion module
by Chengeng Qian 04 Nov '22

04 Nov '22

******************* This email originates from outside Imperial. Do not click on links and attachments unless you recognise the sender. If you trust the sender, add them to your safe senders list https://spam.ic.ac.uk/SpamConsole/Senders.aspx to disable email stamping for this address. ******************* Hi, I am a beginner of Nektar++. I note that there is a lecture named *Development of a Combustion Module within the Nektar++ Framework *in the Nektar++ Workshop 2022. However, I didn't see any examples of combustion simulation in the tutorials. Is there someone know how to use combustion module in Nektar++? Regrads Chengeng

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Linearized NS equation with forcing term
by Emily Smith 31 Oct '22

31 Oct '22

******************* This email originates from outside Imperial. Do not click on links and attachments unless you recognise the sender. If you trust the sender, add them to your safe senders list https://spam.ic.ac.uk/SpamConsole/Senders.aspx to disable email stamping for this address. ******************* Dear Nektar++ community, I want to solve the evolution equations for the OTD modes using Nektar++. I would be grateful if you could read my question in the attached pdf file because it has some formulas. With best regards, Emily

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AeroForces filter calculation in 3DH1D problem with XYofZ mapping
by paulohferr＠yahoo.com 30 Oct '22

30 Oct '22

******************* This email originates from outside Imperial. Do not click on links and attachments unless you recognise the sender. If you trust the sender, add them to your safe senders list https://spam.ic.ac.uk/SpamConsole/Senders.aspx to disable email stamping for this address. ******************* Hi all, I would like to know if, by using the XYofZ mapping in a quasi-3D problem with a Fourier expansion in the Z direction, will the AeroForces filter provide me with the resulting forces calculated in the transformed coordinates, that is, already considering the forces integrated over the surface of the three-dimensional body resulting from the transformation, and decomposed in each direction (X and Y)? Or should I use another filter or another way to obtain the temporal history of forces in this case? Thanks in advance. Best regards,Paulo Henrique

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isocontour Module
by İlteber Özdemir 28 Oct '22

28 Oct '22

******************* This email originates from outside Imperial. Do not click on links and attachments unless you recognise the sender. If you trust the sender, add them to your safe senders list https://spam.ic.ac.uk/SpamConsole/Senders.aspx to disable email stamping for this address. ******************* Hi, I was trying to use the isocontour module of FieldConvert, and first tried a very simple case. When I load the dat file to ParaView using Tecplot Viewer, I get the whole mesh and the fields with it. So, it is not a set of points of the isocontour (should be a set of lines in my case). I also checked the dat file, the first line is Variables = x, y, u, v, p. Is it possible that the module does not work for 2D? The command I am using is: FieldConvert -v -m isocontour:fieldid=0:fieldvalue=0.0:smooth:globalcondense:removesmallcontour=100 timeSteps/mesh.xml system/session.xml timeSteps/chkFiles/mesh_135.chk/ out.dat or FieldConvert -v -m isocontour:fieldid=0:fieldvalue=0.0 timeSteps/mesh.xml system/session.xml timeSteps/chkFiles/mesh_135.chk/ out.dat I check the contours from ParaView, and what I am trying to get (u=0 lines) exists. I would be happy if you can help me with this. PS: On page 121 of the user guide (5.2.0), there is a typo: "5.6.22 Isocontour extraction: iscontour module" (should be isocontour module). Kind regards, Ilteber

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Parallelisation Study of Nektar++
by İlteber Özdemir 25 Oct '22

25 Oct '22

******************* This email originates from outside Imperial. Do not click on links and attachments unless you recognise the sender. If you trust the sender, add them to your safe senders list https://spam.ic.ac.uk/SpamConsole/Senders.aspx to disable email stamping for this address. ******************* Hello all, Is there a study on the optimum amount of nodes per core in Nektar++? What is the recommended number of elements per core when using the solvers in parallel, and how is this affected by the order of the solution used? The same goes for memory used too: what is the recommended memory when using Nektar++ in parallel? Thank you in advance for the help! Best regards, Ilteber -- İlteber R. Özdemir

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Build Nektar++ with MPI parallelisation
by m.r.rouhanian＠ut.ac.ir 24 Oct '22

24 Oct '22

******************* This email originates from outside Imperial. Do not click on links and attachments unless you recognise the sender. If you trust the sender, add them to your safe senders list https://spam.ic.ac.uk/SpamConsole/Senders.aspx to disable email stamping for this address. ******************* Dear all, I want to run a solver in parallel. I compile using MPI and enable the NEKTAR_USE_MPI option in the CMake configuration. unfortunately, I got this error when running make install: collect2: error: ld returned 1 exit status library/UnitTests/CMakeFiles/UnitTests.dir/build.make:558: recipe for target 'library/UnitTests/UnitTests-3.2.0' failed make[2]: *** [library/UnitTests/UnitTests-3.2.0] Error 1 CMakeFiles/Makefile2:639: recipe for target 'library/UnitTests/CMakeFiles/UnitTests.dir/all' failed make[1]: *** [library/UnitTests/CMakeFiles/UnitTests.dir/all] Error 2 Makefile:160: recipe for target 'all' failed make: *** [all] Error 2 Do you know what the problem is and how I should fix it? Best Regards, MohammadReza

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Errors in running Comp Flow simulation with 'nummode=1'
by Kumar, Varun 08 Oct '22

08 Oct '22

******************* This email originates from outside Imperial. Do not click on links and attachments unless you recognise the sender. If you trust the sender, add them to your safe senders list https://spam.ic.ac.uk/SpamConsole/Senders.aspx to disable email stamping for this address. ******************* Hello, I am comparing the simulation results for different Polynomial orders for compressible flow over a NACA airfoil. However, it appears that for order=1, the simulation crashes immediately with the error log attached here. I also attach the mesh and sessions file in the ZIP folder for reference. Any insights into this would be greatly appreciated. -- Varun Kumar Doctoral candidate (Engineering) 170 Hope St Brown University

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how to set a a forced oscillating cylinder by nektar++, in which the cylinder's velocity and displacement are read from a file.
by hongfu2233 29 Sep '22

29 Sep '22

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Some questions about Nektar++ in the VIV simulation
by Zhipeng Yu 28 Sep '22

28 Sep '22

******************* This email originates from outside Imperial. Do not click on links and attachments unless you recognise the sender. If you trust the sender, add them to your safe senders list https://spam.ic.ac.uk/SpamConsole/Senders.aspx to disable email stamping for this address. ******************* Dear sir I am a PHD student from Tsinghua Univerity in China. I am writing this letter to enquire some questions about Nektar++ v5.2.0. When the simulation about the VIV of a rigid cylinder are carried out by Nektar++, the Dis_y showed the same value in z direction. However, the Vel_y and Acel_y presented different values in z direction at the same time is quite different. It seems that the Vel_y and Acel_y should be the same value in the z direction for a rigid cylinder. The results are presented as follow. # Time z Disp_x Vel_x Acel_x Disp_y Vel_y Acel_y 400 0 0 0 0 0.00419954 -0.0018539027 -0.0046684539 400 0.19635 0 0 0 0.00419954 -0.0018539026 -0.0046731296 400 0.392699 0 0 0 0.00419954 -0.0018539025 -0.004678392 400 0.589049 0 0 0 0.00419954 -0.0018539025 -0.0046851524 400 0.785398 0 0 0 0.00419954 -0.0018539025 -0.0046888038 400 0.981748 0 0 0 0.00419954 -0.0018539025 -0.004685259 400 1.1781 0 0 0 0.00419954 -0.0018539026 -0.0046771037 400 1.37445 0 0 0 0.00419954 -0.0018539027 -0.00466885 400 1.5708 0 0 0 0.00419954 -0.0018539028 -0.0046617006 400 1.76715 0 0 0 0.00419954 -0.0018539029 -0.004654695 400 1.9635 0 0 0 0.00419954 -0.0018539029 -0.0046481107 400 2.15984 0 0 0 0.00419954 -0.001853903 -0.0046443416 400 2.35619 0 0 0 0.00419954 -0.001853903 -0.0046429716 400 2.55254 0 0 0 0.00419954 -0.0018539029 -0.0046455258 400 2.74889 0 0 0 0.00419954 -0.0018539029 -0.0046517606 400 2.94524 0 0 0 0.00419954 -0.0018539028 -0.0046603436 Thank you for your patient. Best regards.

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