Dear All, I have two questions in regard to the usage of the Nektar++ 4.2.0. 1. Is it possible to define time-dependent body-force for the Incompressible Navier-Stokes solver? Could anyone send me an example? 2. I read in the User Giude that the definition of the geometry can be stored in separate from the remaining configuration. It is not obvious for me how the solver will identify then the geometry or the configuration elements. In this case how should I call the IncNavierStokesSolver? Could anybody send me an example? I really appreciate any help. Best regards, Péter
Dear Peter,
I have two questions in regard to the usage of the Nektar++ 4.2.0.
1. Is it possible to define time-dependent body-force for the Incompressible Navier-Stokes solver? Could anyone send me an example?
Looking at the user-guide for 4.2.0 it was possible to specify a time dependent modulation to the forcing function Absorption so the general functionality is there. I am not however sure that the Body force module. I have just looked at the ForcingBody.cpp in 4.3.0 and it does allow for a time function scaling, i.e. f(x,y,z,t) = f(x,y,z) * g(t) so that g(t) could be specified. However the user-guide does not say how to do this. @douglas @yumnah do you have an example you could send us? (PS we should probably put some explanation for this in the user guide)
2. I read in the User Giude that the definition of the geometry can be stored in separate from the remaining configuration. It is not obvious for me how the solver will identify then the geometry or the configuration elements. In this case how should I call the IncNavierStokesSolver? Could anybody send me an example?
The mesh geometry is contained in the xml tag <GEOMETRY> where as other boundary condition are in an xml tag <CONDITIONS>. Therefore you can make two files one containing file_geometry.xml <NEKTAR> <GEOMETRY> …. </GEOMETRY> </NEKTAR> and another file specifying conditions and the expansion file_conditions.xml <NEKTAR> <EXPANSIONS> …. </EXPANSIONS> <CONDITIONS> …. </CONDIITONS> </NEKTAR> You can then execute the files by writing soothing like ./IncNavierStokesSolver file_geometry.xml file_conditions.xml If you have specified duplicate sections it will read the second file except in the case when the region is empty when it should ignore the empty tag (at least in 4.3.0). Hope this help, Spencer PS If you have some suggested text for the user guide that would have helped with these issue could I ask if you can send this back to us so we can continue to improve this part of the framework.
I really appreciate any help.
Best regards, Péter
_______________________________________________ Nektar-users mailing list Nektar-users@imperial.ac.uk https://mailman.ic.ac.uk/mailman/listinfo/nektar-users
Spencer Sherwin McLaren Racing/Royal Academy of Engineering Research Chair, Professor of Computational Fluid Mechanics, Department of Aeronautics, Imperial College London South Kensington Campus London SW7 2AZ s.sherwin@imperial.ac.uk +44 (0) 20 759 45052
Hi Peter, hi Spencer, I don't actually use the body force, but I think the way to specify a time modulation is: <CONDITIONS> ... <FUNCTION NAME="BodyForce"> <E VAR="u" VALUE="y*x" /> <E VAR="v" VALUE="1" /> </FUNCTION> </CONDITIONS> <FORCING> <FORCE TYPE="Body"> <BODYFORCE> BodyForce </BODYFORCE> <BODYFORCETIMEFCN> cos(t) </BODYFORCETIMEFCN> </FORCE> </FORCING> I do not know however if this was already available in 4.2.0. Cheers, Douglas ________________________________________ From: nektar-users-bounces@imperial.ac.uk <nektar-users-bounces@imperial.ac.uk> on behalf of Sherwin, Spencer J <s.sherwin@imperial.ac.uk> Sent: 02 May 2016 11:49 To: Péter Tamás Nagy Cc: nektar-users Subject: Re: [Nektar-users] Time dependent bodyforce Dear Peter,
I have two questions in regard to the usage of the Nektar++ 4.2.0.
1. Is it possible to define time-dependent body-force for the Incompressible Navier-Stokes solver? Could anyone send me an example?
Looking at the user-guide for 4.2.0 it was possible to specify a time dependent modulation to the forcing function Absorption so the general functionality is there. I am not however sure that the Body force module. I have just looked at the ForcingBody.cpp in 4.3.0 and it does allow for a time function scaling, i.e. f(x,y,z,t) = f(x,y,z) * g(t) so that g(t) could be specified. However the user-guide does not say how to do this. @douglas @yumnah do you have an example you could send us? (PS we should probably put some explanation for this in the user guide)
2. I read in the User Giude that the definition of the geometry can be stored in separate from the remaining configuration. It is not obvious for me how the solver will identify then the geometry or the configuration elements. In this case how should I call the IncNavierStokesSolver? Could anybody send me an example?
The mesh geometry is contained in the xml tag <GEOMETRY> where as other boundary condition are in an xml tag <CONDITIONS>. Therefore you can make two files one containing file_geometry.xml <NEKTAR> <GEOMETRY> …. </GEOMETRY> </NEKTAR> and another file specifying conditions and the expansion file_conditions.xml <NEKTAR> <EXPANSIONS> …. </EXPANSIONS> <CONDITIONS> …. </CONDIITONS> </NEKTAR> You can then execute the files by writing soothing like ./IncNavierStokesSolver file_geometry.xml file_conditions.xml If you have specified duplicate sections it will read the second file except in the case when the region is empty when it should ignore the empty tag (at least in 4.3.0). Hope this help, Spencer PS If you have some suggested text for the user guide that would have helped with these issue could I ask if you can send this back to us so we can continue to improve this part of the framework.
I really appreciate any help.
Best regards, Péter
_______________________________________________ Nektar-users mailing list Nektar-users@imperial.ac.uk https://mailman.ic.ac.uk/mailman/listinfo/nektar-users
Spencer Sherwin McLaren Racing/Royal Academy of Engineering Research Chair, Professor of Computational Fluid Mechanics, Department of Aeronautics, Imperial College London South Kensington Campus London SW7 2AZ s.sherwin@imperial.ac.uk +44 (0) 20 759 45052 _______________________________________________ Nektar-users mailing list Nektar-users@imperial.ac.uk https://mailman.ic.ac.uk/mailman/listinfo/nektar-users
participants (3)
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Péter Tamás Nagy
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Serson, Douglas
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Sherwin, Spencer J