- Nektar-users - imperial.ac.uk

Aerodynamic forces
by Alessandro Alberto de Lima 18 Jun '21

18 Jun '21

******************* 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 Guys, I would like to know how the aerodynamic forces are calculated in nektar, the dimensions of the values on the .fce output file and its relation with the aerodynamic coefficients. Thank you. Alessandro

2 1

Boundary layer mesh
by Ezat Shokrani 12 Jun '21

12 Jun '21

******************* 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++ developers, I am working on numerical simulation of blood flow in arteries. The flow regime of my case study is laminar. In addition to obtaining velocity and pressure field, the evaluation of shear rate and WSS for this case is also important for me. Therefore, in addition to using tetrahedral elements as core mesh, I am going to employ prism layers for resolving the boundary layer next to the wall. I have seen, in the literature, that there are two approaches for producing the boundary layer mesh that most groups use them. Firstly, some groups consider a constant total thickness for boundary layer mesh. This means that during the mesh study process, they do not change the overall thickness but they try to increase the number of layers. Secondly, other groups consider a constant number of layers for the boundary layer mesh (e.g. three layers for the coarse mesh) during the mesh study and when they refine the mesh in each step, the element size of each layer decreases. As a result, the total thickness of boundary layer mesh decreases too. Meanwhile, I have encountered some questions related to these approaches for producing boundary layer mesh. I have seen in articles related to the blood flow simulation which is done using Nektar++, p-refinement method has been used for mesh study process which I think this mimics the first approach. My question is that how I can calculate the total thickness of the boundary layer mesh (both steady and pulsatile flow conditions) through the mesh study. Related to the second approach, I have seen different research teams have various opinions for constructing the boundary layer mesh even for the cases with similar geometry and flow conditions. For example, different groups produce boundary layer mesh with a range of 3 to 20 layers. In addition, some consider a constant thickness for “each” layer (with no growth factor). However, others try to use a growth factor to vary the thickness of each layer. Even, different groups use a variety of core element size to boundary layer size ratio to construct the mesh. I know that this depends on the case study but they did not mention any reason for their choices. I would like to know whether or not there is a rule of thumb for this process or if there is a good guess for producing the boundary layer mesh with respect to this approach. I would be wondering if you could guide me on these issues. Best regards, Ezat Shokrani,

2 1

NekMesh statistics per element type
by Vidhi Zala 12 Jun '21

12 Jun '21

******************* 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 able to get some statistics while generating XML from msh using the verbose mode of NekMesh. However, it provides information in aggregate 2D and 3D elements. I wonder if there is a method to query NekMesh that provides details on the distribution of 2D and 3D elements? Thanks, V -- ,-~~-.___._. / | ' \ | |--------. Vidhi Zala ( ) 0 | | | School of Computing \_/-, ,----' | | | Scientific Computing and Imaging Institute ==== !_!-v---v--. University of Utah / \-'~; .--------. / __/~| ._-""|| | vidhi.zala(a)utah.edu =( _____|_|____||________| http://sci.utah.edu/people/vidhi.html

1 0

Problem to install Nektar++ 5.0.1 in macOS Catalina 10.15.7
by Eduardo Lopez Bravo 09 Jun '21

09 Jun '21

******************* 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 Nektar team, I'm brand new on Nektar++ community. I've been trying to install Nektar++ on my macOS Catalina 10.15.7 but nothing seems to work. I've taken a screenshot of the error message while I tried to configure Nektar dependencies following the user manual. I have installed the seven packages required using Homebrew, and additionally I have installed some other packages (METIS, FFTW, Open Cascade CE, Tetgen and Triangle). Not only that, but I've been trying to install the latest version of Nektar on my macOS, but I haven't succeeded. That's the main reason I have tried it with the 5.0.1 version. If someone has succeeded at installing Nektar++ in this macOS version, could you please tell me what you did so it can work? Any help will be extremely appreciated! Kind regards, Eduardo. PD: I suspected there is a problem among CMAKE Version 3.20.3 and BLAS/LAPACK packages. [image: Error message Nektar.png]

2 1

Some problems with post-processing FieldConvert
by gongminjiang＠hrbeu.edu.cn 08 Jun '21

08 Jun '21

******************* 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 want to generate Q-criterion and vorticity isocontour in Tecplot, and also I use C0Projeciton to smooth data, but the visualization quality is not good. Do I still have some skills to make the isocontour smooth? Best wishes!

2 1

Stretching existing mesh using Nekmesh
by Vidhi Zala 31 May '21

31 May '21

******************* 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 have a nekmesh question - Can I use nekmesh to take an existing 2D mesh in [image: [0,1]\times[0,1]] and stretch it t/o [image: [-10, 10] \times [-10,10]] ? Thanks V -- ,-~~-.___._. / | ' \ | |--------. Vidhi Zala ( ) 0 | | | School of Computing \_/-, ,----' | | | Scientific Computing and Imaging Institute ==== !_!-v---v--. University of Utah / \-'~; .--------. / __/~| ._-""|| | vidhi.zala(a)utah.edu =( _____|_|____||________| http://sci.utah.edu/people/vidhi.html I support Ruff Haven Crises Shelter for Homeless Pets <https://www.ruffhaven.org/donate>. Consider a donation today :)

3 5

flow over airfoil
by Mahdi Erfanian Nakhchi 24 May '21

24 May '21

******************* 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 NEKTAR++ users, I have a quick question. I want to see if it is possible to use FFT to perform simulations over an airfoil with vortex generators on its surface. (Picture below) Or it can only be simulated in full 3D shape? Many thanks Mahdi Postdoc Research Fellow, Northumbria University [cid:561eba87-0128-4c9c-ad88-c1ec49d450c7] This message is intended solely for the addressee and may contain confidential and/or legally privileged information. Any use, disclosure or reproduction without the sender's explicit consent is unauthorised and may be unlawful. If you have received this message in error, please notify Northumbria University immediately and permanently delete it. Any views or opinions expressed in this message are solely those of the author and do not necessarily represent those of the University. Northumbria University email is provided by Microsoft Office365 and is hosted within the EEA, although some information may be replicated globally for backup purposes. The University cannot guarantee that this message or any attachment is virus free or has not been intercepted and/or amended.

1 0

3D channel flow stability analysis not working in parallel?
by Xiao, Chengnian 17 May '21

17 May '21

******************* 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 have been running nektar++-5.0.2 and trying the 3D stability analysis for the channel flow as described in the specific nektar tutorial. I used the session file "PPF_R10000_3D.xml" provided under the /Tests subdirectory of IncNavierStokesSolver, and obtained the same complex eigenvalues 0.518448+/-26.6405i as the tutorial when I ran the problem on a single processor. However, when I executed the same session on multiple (4) processors, the two eigenvalues upon convergence were different, namely -6.957 +/-1.34189i. The corresponding eigenvectors also looked completely different than the results shown in the tutorial file. I experienced no such problems, however, when I ran the stability analysis with the "MultipleModes" option. Could there be an issue with the "SingleMode" option on multiple processors? I would be very grateful for your assistance. Best regards, Cheng

1 0

doxygen documentation TimeIntegrationScheme
by Martin Wilfried Hess 17 May '21

17 May '21

******************* 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++ developers, I am using the current master branch to implement time-dependent model reduction for incompressible CFD. The current doxygen documentation has deviated significantly from the code. For example I cannot reconstruct what happened to Nektar::LibUtilities::TimeIntegrationScheme Class Reference as documented here https://doc.nektar.info/doxygen/latest/class_nektar_1_1_lib_utilities_1_1_t… Martin -- -- Martin Hess, Ph.D., Post-doctoral research fellow SISSA mathLab, International School for Advanced Studies Office A-434 (4th floor), via Bonomea 265, I-34136 Trieste, Italy phone: +39 040 3787 491 email: mhess(a)sissa.it

1 0

Element-specific filter architecture
by Vidhi Zala 14 May '21

14 May '21

******************* 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 working on adding a filter in accordance with the SolverUtils/Filter architecture. It performs element-type specific operations. Instead of creating a monolithic filter that checks for the element type and performs operations, I want to break it down into subfilters. Should these go into StdRegions/ since they are element-specific or stay in SolverUtils? It will help if someone can point to an example scenario of an existing filter designed this way. Thanks, V ,-~~-.___._. / | ' \ | |--------. Vidhi Zala ( ) 0 | | | School of Computing \_/-, ,----' | | | Scientific Computing and Imaging Institute ==== !_!-v---v--. University of Utah / \-'~; .--------. / __/~| ._-""|| | vidhi.zala(a)utah.edu =( _____|_|____||________| http://sci.utah.edu/people/vidhi.html I support Ruff Haven Crises Shelter for Homeless Pets <https://www.ruffhaven.org/donate>. Consider a donation today :)

1 0