May 2024 - Nektar-users - imperial.ac.uk

AeroForces definition
by Daniel Rubano Barretto Turci 29 May '24

29 May '24

******************* 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 am running an 2D incompressible Navier Stokes simulation with a dimensionless setup and using the AerForces filter. I am trying to reproduce results from the literature that use the drag coefficient defined as Cd = 2*Fd/(rho*U*U*D), where Fd is the drag force per unit of length and D is the diameter of a cylinder. I wish to know whether the value exported to the file DragLift.fce is half the Cd as defined previously or the Cd itself. I think it is the former, but I would like a confirmation. For reference, I am sending a snippet of the session xml file. <SOLVERINFO> </SOLVERINFO> <PARAMETERS> TimeStep = 0.01 FinTime = 20 NumSteps = FinTime/TimeStep IO_CheckSteps = NumSteps/20 IO_InfoSteps = 5 IO_FiltersInfoSteps = 100 IO_CFLSteps = 10 Re = 66 Kinvis = 1/Re </PARAMETERS> <FILTERS> <FILTER TYPE="AeroForces"> <PARAM NAME="OutputFile"> DragLift </PARAM> <PARAM NAME="OutputFrequency"> 5 </PARAM> <PARAM NAME="Boundary"> B[3] </PARAM> </FILTER> -- Daniel Rubano B. Turci D. Sc. Student at Universidade Federal Fluminense (UFF). Laboratory of Thermal Sciences - LATERMO. *Rua Passo da Pátria, 156, Bloco D, sala 302, Niterói. RJ - 24210-240, Brazil.*

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Spatial two-point correlation
by Alexander Schukmann 28 May '24

28 May '24

******************* 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 everybody, I was wondering, if there is a way to calculate spatial two-point correlation functions such as R_uu = < u(x,t) * u(x + r,t) > within Nektar++. Here, "u" is a scalar function, such as streamwise velocity, "< >" denotes a temporal average and "r" is a spatial separation distance. My first idea was to use the HistoryPoints Filter, hence tracking the scalar along a line for each time step and calculating R_uu during postprocessing. But maybe there exists a more efficient way using a combination of Nektar++ Filters/Functions? I appreciate any help on the topic. All the best Alex Sicher versendet mit [Proton Mail](https://proton.me/).

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Sponge region setup in the acoustic solver
by Nande, Ishan A. 25 May '24

25 May '24

******************* 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 using the Acoustic solver to solve Linearized Euler Equations. I wish to use a sponge region in my setup. I have gone through the user guide and test cases but I am unable to understand how the coefficients are actually being applied in the sponge region. If I refer to Sec 3.6.1 of the v5.5.0 user guide, it says that the coefficient's values can be defined using the variable "r" and this variable can be used to control the distance to the sponge region. So, are we specifying the distance to the sponge region or, the values of coefficients in the sponge region ? If it's the former, does it mean that damping of waves will automatically be applied by Nektar++? I set-up a very simple 1D initial-value problem where a Gaussian pulse placed at the centre of -100 <= x <= 100 travels in left-right direction. I set-up the evaluation of "r" as a linear increase from -0.2 to 0 from x=60 to x=100. I was expecting that the pulse in the right will completely vanish as it reaches x=100. This was however not the case. I assumed that the amplitude of the pressure pulse will be multiplied by the values from -0.2 to 0. Can someone please provide some clarity on this ? Regards, Ishan PGR

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Error in test cases
by Mahdi Riazat 21 May '24

21 May '24

******************* 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/Madam, I am PhD student at Concordia University and I want to use Nektar++ for an FSI simulation. I installed Nektar++ and want to run CylFlow_HomoStrip.xml case as a starting point however I got the following error: "Required parameter 'HomStructModesZ' not specified in session". I appreciate it if you can help me with this. Best regards, Mahdi Riazat

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Re: [Nektar-users] WSS taking too much time
by Ehsan Asgari 20 May '24

20 May '24

Thank you Guglielmo and Selman I tried C0Projection method but I ended up with the following distribution: [image: image.png] As you see there is so much oscillation! I wonder how smooth your results are with WSS. syavash On Mon, May 20, 2024 at 2:56 PM Vivarelli, Guglielmo A < guglielmo.vivarelli12(a)imperial.ac.uk> wrote: > Hi Syavash, > > Try: > > FieldConvert -m C0Projection test.xml test.fld test-C0Proj.fld > > Regards, > > Guglielmo > ------------------------------ > *From:* Ehsan Asgari <eh.asgari(a)gmail.com> > *Sent:* 20 May 2024 18:52 > *To:* Vivarelli, Guglielmo A <guglielmo.vivarelli12(a)imperial.ac.uk> > *Subject:* Re: [Nektar-users] WSS taking too much time > > Thanks Guglielmo > > It worked! > However, the result is not satisfactory. I have a smooth velocity field > but the wall shear stress exhibits discontinuities, likely due to C1 issue. > Could you suggest a remedy? > > syavash > > > > > On Mon, May 20, 2024 at 1:50 PM Vivarelli, Guglielmo A < > guglielmo.vivarelli12(a)imperial.ac.uk> wrote: > > Hi Syawash, > > Try: > > "mpirun -np *your_cores* FieldConvert -m wss:bnd=3 <mesh.xml> > <session.xml> <time-averaged.fld> <time-averaged-wss.fld>" > > Regards, > > Guglielmo > ------------------------------ > *From:* nektar-users-bounces(a)imperial.ac.uk < > nektar-users-bounces(a)imperial.ac.uk> on behalf of Ehsan Asgari < > eh.asgari(a)gmail.com> > *Sent:* 20 May 2024 17:48 > *To:* nektar-users <nektar-users(a)imperial.ac.uk> > *Subject:* [Nektar-users] WSS taking too much time > > > This email from eh.asgari(a)gmail.com 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 am trying to extract the wall shear stress for a 2.5-D case using the > wss module: > > FieldConvert -m wss:bnd=3 <mesh.xml> <session.xml> <time-averaged.fld> <time-averaged-wss.fld> > > However, it is taking too much time to execute, more than 1 hour with no output. > > I noticed another report on this issue in the mail archive, not sure if my case has the same problem. > > > I appreciate any help you can provide. > > syavash > > >

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WSS taking too much time
by Ehsan Asgari 20 May '24

20 May '24

******************* 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 am trying to extract the wall shear stress for a 2.5-D case using the wss module: FieldConvert -m wss:bnd=3 <mesh.xml> <session.xml> <time-averaged.fld> <time-averaged-wss.fld> However, it is taking too much time to execute, more than 1 hour with no output. I noticed another report on this issue in the mail archive, not sure if my case has the same problem. I appreciate any help you can provide. syavash

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NekMesh: Inconsistent triangular face orientation
by Alexander Schukmann 20 May '24

20 May '24

******************* 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 everybody, I tried converting a 3D tetra/prism mesh (generated with gmsh) of a simple cylinder from msh to xml using NekMesh. The domain has periodic boundaries along the cylinder axis. However, I receive the following error: Orientation of triangular face (id = 113069) is inconsistent with face 3 of prism element (id = 55392) since Dir2 is aligned with Dir1. Mesh setup needs investigation terminate called after throwing an instance of 'Nektar::ErrorUtil::NekError' I've seen a similar post from May 12th, where it was suggested to try the peralign option, so I used: NekMesh -m peralign:surf1=700:surf2=800:dir=z:orient CylReD3900.msh CylReD3900.xml with no success. The two surface IDs 700 and 800 of course refer to the periodic boundary faces. I attached my msh file and appreciate any help. All the best Alex Sicher versendet mit [Proton Mail](https://proton.me/).

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ARPACK is not set-up for parallel execution
by 🌸那慢慢🌸 15 May '24

15 May '24

******************* 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 and developers, I get the error "ARPACK is not set-up for parallel execution" when running the incompressbile flow solver in parallel with MPI，but in the file build/CMakeCache.tst have a line saying:NEKTAR_USE_MPI:BOOL=ON.How do I fix this? Hongtao Cheng

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Acoustic solver Source term
by dauood Tariq 13 May '24

13 May '24

******************* 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 trying to understand the source term provided in the user guide however the equation for the source term is very confusing and I cannot find any information on it. I would appreciate it. Regards, Dauood

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(no subject)
by Wang Tongkuai 12 May '24

12 May '24

******************* 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. ******************* 从 Windows 版邮件发送 Dear All, I meshed a cylinder with hexas and prisms at gmsh with no error. Here is the problem occurred when I NekMesh it: Orientation of triangular face (id = 10638) is inconsistent with face 3 of prism element (id = 3588) since Dir2 is aligned with Dir1. Mesh setup needs investigation terminate called after throwing an instance of 'Nektar::ErrorUtil::NekError' I don’t know which surface is face 3 and how does the inconsistency happen. Dir 1 and Dir 2 are x- and y-axis direction, right? A half of y-z plane is shown. Regards, Tongkuai.

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