- Nektar-users - imperial.ac.uk

Homoplane module wavespace output
by Guillermo 01 Aug '19

01 Aug '19

Dear all, I am using the homplane FieldConvert module with the wavespace option , but I do not completely understand the output (fld) result. I have performed a quasi 3D simulation, with up to 3 Fourier modes (HomModesZ = 4). Then, I use the FieldConvert -m homplane:wavespace:planeid=<value> ... command to obtain the Fourier coefficients. I have extracted 4 different planes, i.e. value={0,1,2,3}. I would like to know what is the information contained in the fld output files. Does planeid=0 and planeid=1 correspond to the real and the imaginary parts, respectively, of the Fourier coefficient for the mode 0, and planeid=2 and planeid=3 correspond to the real and the imaginary parts, respectively, of the Fourier coefficient for the mode +-1? Thank you in advance. Regards, Guillermo

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Generating Gaussian random process for velocity boundary conditions
by Akhavan Safaei, Ali 01 Aug '19

01 Aug '19

Hello everyone, I need to generate a velocity boundary condition for IncNavierStokesSolver as a Gaussian random process (in time) in the session file. I know we can use "awgn(sigma)", for example, to generate Gaussain random I.C.; but, I haven't been able to fine a way to extend it to random process B.C. . I would greatly appreciate it if anyone can help me with that. Best, Ali Akhavan-Safaei ---------------------------------------------------------------------------------- Ali Akhavan Safaei, PhD student, Graduate Research Assistant Michigan State University Department of Mechanical Engineering 428 S. Shaw Lane Engineering Bldg., Rm. #4110 East Lansing, MI 48824 Email: akhavans(a)msu.edu akhavans(a)egr.msu.edu ----------------------------------------------------------------------------------

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p adaption for compressible flow solver
by 蒋树杰 23 Jul '19

23 Jul '19

Hi All, I am using Nektar++ compressible flow solver. I noticed the p-adaptive algorithm can be used to optimize the computational cost. I have read the user guide but I still do not know how to perform it. I just add the AdaptiveModes and AdaptiveMinModes in the parameters. The SolverInfo like this: <SOLVERINFO> </SOLVERINFO> I use FieldConver -m nummodes to see the polynomial order distributions. But it seems the polynomial order is not changed in the fields. Does anyone familiar with it? I found a paper in 2013 about an inviscid transonic flow past a NACA0012 airfoil. I think this approach can be done by compressible flow solver. Many thanks for your help! Shujie University of Southampton

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Time-average field can not be used in a quasi 3d simualtion by the compressible solver
by 蒋树杰 18 Jul '19

18 Jul '19

Hi All, I found the time-average field can not be used in a quasi 3d simulation by the compressible solver. it comes with the error: [ubuntu:10117] *** Process received signal *** [ubuntu:10117] Signal: Segmentation fault (11) [ubuntu:10117] Signal code: Address not mapped (1) [ubuntu:10117] Failing at address: 0x208 [ubuntu:10117] [ 0] /lib/x86_64-linux-gnu/libc.so.6(+0x354b0)[0x7f5bcb64d4b0] [ubuntu:10117] [ 1] /home/shujie/nektar++/build/dist/lib64/libSolverUtils.so.5.0.0b(_ZN6Nektar10FieldUtils5Field13AppendExpListEiNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEEb+0x74)[0x7f5bce1ac454] [ubuntu:10117] [ 2] /home/shujie/nektar++/build/dist/lib64/libSolverUtils.so.5.0.0b(_ZN6Nektar11SolverUtils18FilterFieldConvert12CreateFieldsERKNS_5ArrayINS_4OneDEKSt10shared_ptrINS_12MultiRegions7ExpListEEEE+0x334)[0x7f5bce1a6254] [ubuntu:10117] [ 3] /home/shujie/nektar++/build/dist/lib64/libSolverUtils.so.5.0.0b(_ZN6Nektar11SolverUtils18FilterFieldConvert11OutputFieldERKNS_5ArrayINS_4OneDEKSt10shared_ptrINS_12MultiRegions7ExpListEEEEi+0xd1)[0x7f5bce1a8641] [ubuntu:10117] [ 4] /home/shujie/nektar++/build/dist/lib64/libSolverUtils.so.5.0.0b(_ZN6Nektar11SolverUtils18FilterFieldConvert8v_UpdateERKNS_5ArrayINS_4OneDEKSt10shared_ptrINS_12MultiRegions7ExpListEEEERKd+0x417)[0x7f5bce1a9337] [ubuntu:10117] [ 5] /home/shujie/nektar++/build/dist/lib64/libSolverUtils.so.5.0.0b(_ZN6Nektar11SolverUtils14UnsteadySystem9v_DoSolveEv+0xddf)[0x7f5bce1bbc2f] [ubuntu:10117] [ 6] /home/shujie/nektar++/build/dist/lib64/libSolverUtils.so.5.0.0b(_ZN6Nektar11SolverUtils14DriverStandard9v_ExecuteERSo+0x8e)[0x7f5bce1724ee] [ubuntu:10117] [ 7] CompressibleFlowSolver(main+0x27d)[0x4798cd] [ubuntu:10117] [ 8] /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf0)[0x7f5bcb638830] [ubuntu:10117] [ 9] CompressibleFlowSolver(_start+0x29)[0x4909a9] [ubuntu:10117] *** End of error message *** I put the test file on the attachment. I have tested it in Incompressible flow solver. It is fine. So I think maybe there is a bug in the compressible flow solver. But I am not looking deep into the code. So I can not find the problem. If someone has a solution, please let me. Kind regards, Shujie University of Southampton

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Regarding in FieldConvert
by Abhishek Kumar 16 Jul '19

16 Jul '19

Hi, Is it possible to delete a field from .fld file using FieldCovert? With regards Abhishek -- --------------------------------------------------------------------------------------- Abhishek Kumar Research Associate Centre for Fluid and Complex Systems Coventry University, Coventry CV15FB United Kingdom Webpage: https://abhishekkir.wixsite.com/website Email # ac7600(a)coventry.ac.uk, abhishek.kir(a)gmail.com Phone: +44 24 7765 9150 Mobile: +44 7464026494 ---------------------------------------------------------------------------------------

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y plus
by Vishal Saini 16 Jul '19

16 Jul '19

Hi all, Please, could anyone suggest an easy way to calculate y+ from an *AverageTurbStatsFile.fld* within Nektar++? Would it take into account the true distribution of expansion point locations? BR, Vishal --- *Vishal SAINI*

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Re: [Nektar-users] 答复: About the periodic boundary condition on quasi-3D simulation
by Yan, Zhenguo 09 Jul '19

09 Jul '19

Hi Shujie, I am not very familiar with the usage of NekMesh, but one reason that may lead to negative Jacobian is that the mesh near the wall is too coarse. This means one element cut across large radian and easily leads to negative Jacobian. I believe Joaquim has developed some techniques to tackle with this problem. But the easy solution is to use finer mesh where the curvature is large. I think this is also Gicomo's first suggestion. Best wishes, Zhenguo On 08/07/2019 11:34, Jiang S. wrote: > > Dear Giacomo, > > > I tried to use NekMesh to generate the mesh, there are two problems: > > > 1. 3D deformed Jacobian not positive in some elements; > 2. Periodic composites have a different number of elements; > > > Is there any way to let the periodic surface have the same element number? > > Thanks! > Shujie > ------------------------------------------------------------------------ > *发件人:* Castiglioni, Giacomo <g.castiglioni(a)imperial.ac.uk> > *发送时间:* 2019年7月8日 10:30 > *收件人:* Jiang S.; nektar-users; d.moxey(a)exeter.ac.uk; Yan, Zhenguo > *抄送:* Sherwin, Spencer J > *主题:* Re: About the periodic boundary condition on quasi-3D simulation > > Dear Shujie, > > I have used the peralign module many times with success, so I wonder > if the problem comes from somewhere else. > > > A couple of suggestions: > - I tried to generate the mesh from your .geo file and I think the > mesh is too coarse to get the wavy features resolved (I get several > warnings of this sort "Warning: degenerate tetrahedron") > - with the step file you can generate the mesh directly with NekMesh > without having to use Gmsh. > > Cheers, > > Giacomo > > ------------------------------------------------------------------------ > *From:* Jiang S. <Shujie.Jiang(a)soton.ac.uk> > *Sent:* Monday, July 8, 2019 10:05:24 AM > *To:* Castiglioni, Giacomo; nektar-users; d.moxey(a)exeter.ac.uk; Yan, > Zhenguo > *Cc:* Sherwin, Spencer J > *Subject:* About the periodic boundary condition on quasi-3D simulation > > Hi All, > > > I use Gmsh to generate a mesh for quasi-3D simulation. I want to use > periodic boundary conditions in the 'left' and 'right' side. > > > But the Nektar++ comes with the error: > > Fatal : Level 0 assertion violation > Unable to determine triangle orientation > > So I tried to change the mesh normal direction in Gmsh. Then the same > error comes again. > At last, I tried to use peralign in NekMesh, it generated a new mesh, > but the same error comes again. > > Actually, I tried to change the periodic boundary condition to wall > boundary condition. It runs successfully. > > Is there something wrong with my mesh? > > > Many thanks for your help! > Have a nice day! > Shujie

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How to get variable value at a fixed point at every time step when the mesh is moving
by Song Xiang 06 Jul '19

06 Jul '19

Dear all, I would like to get variable value at a fixed point in physical space at every time step. Its coordinates are given as "HistoryPoints". However, my domain is moving and i need find the fixed point in the new mesh at every time step. So, I use the "UpdateGeometry()" in "Deform.cpp" to update mesh at every time step and then use "FillBoundingBoxTree()" in "MeshGraph.cpp" to update rtree so that i can find the id of element the fixed point locating in. However, the "FillBoundingBoxTree()" can not update m_boundingBoxTree according the new mesh and i always get the id of element the fixed point locating in initial mesh. Whether do i need to modify something other? Who can give some suggestions about how to get value at a fixed point in physical space at every time step when the mesh is moving? Thank you very much! Best, Song

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3DH1D History points
by Guillermo 05 Jul '19

05 Jul '19

Dear all, I am conducting a quasi 3D simulation, being the z-axis the homogeneous direction, with an homogeneous length equal to 0.1 (LZ=0.1) and up to 3 Fourier modes (HomModesZ = 4). I am interested on placing some history points along the homogeneous direction, however I am facing several issues which I would like to clarify. - First of all, I have made several tests and it seems that it is not possible to parametrize the points coordinates. I mean, the coordinates do not accept parameters defined on the parameters XML element. The following example does not provide any output result: <PARAM NAME="Points"> 0.0 LZ 0.0 </PARAM> Is there any way to parametrize the coordinates? since it will be very beneficial. - I would like to place probes at LZ/4, LZ/2 and 3*LZ/4, thus I defined the HistoryPoints filter as follows: <PARAM NAME="Points"> 0.0 0.0 0.025 0.0 0.0 0.05 0.0 0.0 0.075 </PARAM> However, I obtain the following 'error' message: Reseting History point from z = 0.075 to z = 0.05. As not Fourier interpolation is required, why do I get this error? - At the FilterHistoryPoints.cpp file I see that it is possible to specify the plane on which to evaluate the history point by using the "OutputPlane" tag. Since I could not find any example, I would like to know how to use this tag, more in precise, how to define the z-coordinate of the points along with the output plane. Is the following example correct? <FILTER TYPE="HistoryPoints"> <PARAM NAME="OutputFile">TimeValues</PARAM> <PARAM NAME="OutputFrequency">10</PARAM> <PARAM NAME="OutputPlane">0,1,2,3</PARAM> <PARAM NAME="Points"> 1 0.5 0 1 0.5 0 1 0.5 0 1 0.5 0 </PARAM> </FILTER> I expect to obtain the measurements at the coordinates (1,0.5,0),(1,0.5,0.025),(1,0.5,0.5),(1,0.5,0.075). - Also at the FilterHistoryPoints.cpp file I have seen that there is another tag, called "WaveSpace". If I implement it, will I obtain the Fourier coefficients on these points? It is somehow confusing to me, so I please you to bring some light into it, and how to use this field. I am using nektar 4.3.3 version and running in parallel with 8 cores. Let me know if you require any other information. With best regards, Guillermo

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hi All, forces file Aerspace filter saving
by Moto Light 28 Jun '19

28 Jun '19

Hi All, I am using AeroForces Filter for getting drag force and lift force, the problem the output file making a problem with time writing for example *This is my filter* <FILTERS> <FILTER TYPE="AeroForces"> <PARAM NAME="OutputFile">stats/stats3/CylinderForces3D</PARAM> <PARAM NAME="OutputFrequency">10</PARAM> <PARAM NAME="Boundary"> B[4] </PARAM> </FILTER> This is my time step TimeStep = 0.0004 which means it must write a new value every 10*0.0004=0.004 but in reality making the same time value *Any suggestions* ******************** 1003 1.1528798 0.0032943811 1.1561741 0.093659336 0.022570084 0.11622942 1003.01 1.1533744 0.0033214418 1.1566958 0.089484878 0.022455566 0.11194044 1003.01 1.1540334 0.0033446732 1.157378 0.085307044 0.022341002 0.10764805 1003.02 1.1546853 0.0033668472 1.1580522 0.081122172 0.022225614 0.10334779 1003.02 1.1553178 0.0033880677 1.1587059 0.076931666 0.022109346 0.099041012 1003.02 1.1559398 0.0034083917 1.1593482 0.072736623 0.021992207 0.09472883 1003.03 1.1565574 0.003427883 1.1599853 0.068536771 0.021874213 0.090410984 1003.03 1.1571725 0.0034465952 1.1606191 0.064331859 0.021755377 0.086087236 1003.04 1.1577834 0.0034645594 1.161248 0.060122116 0.021635717 0.081757833 1003.04 1.158388 0.0034817896 1.1618697 0.055907869 0.021515254 0.077423123 1003.04 1.1589851 0.0034982948 1.1624834 0.051689331 0.021394007 0.073083338 1003.05 1.1595742 0.0035140833 1.1630883 0.04746671 0.021271999 0.068738709 1003.05 1.160154 0.0035291602 1.1636832 0.043240357 0.021149249 0.064389606 ----------- any suggestions to change the time precision Regards, Reda

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