For the past weeks I've been testing nektar for incompressible jets and so far I've been able to compile the code on our cluster and to run some simulations with it too. However, I still have a few questions: A) What is the best way to compute the Reynolds stresses in cylindrical coordinates? In jets, it is common to plot the stresses only as function of the radial coordinate and to average azimuthally (like in pipes). Can the stresses be computed in cylindrical coordinates run time or do I have to save snapshots of 3D-fields to disk and do everything in a post processing step? B) How do I restart a simulation? So far I haven't succeeded with the following approach: -Run simulation for some time to produce jet.fld. -FieldConvert base/jet.xml base/jet.fld restart.fld -mv restart.fld base/restart.rst -Set initial conditions to: <FUNCTION NAME="InitialConditions"> <F VAR="u,v,w,p" FILE="restart.rst" /> </FUNCTION> -IncNavierStokesSolver base/mesh.xml base/jet.xml (the mesh is in separate .xml file) -->Unable to open file: restart.rst C) What is the difference between .chk and .fld? I have a hunch that the .chk files could be used to restart the simulation with much less effort... Petteri Peltonen, (M.Sc.) Aalto University, School of Engineering Department of Mechanical Engineering PO Box 14300 FI-00076 Aalto, Finland +358 44 0554984 petteri.peltonen@aalto.fi
Hi, Regarding B and C. I think you should be able to use any of the .chk, fld, files. In my use I found them equivalent. Not sure if this is a problem, but I see you are calling the solver from a different directory than your mesh.xml and session.xml files are. Try to leave the restart.rst in the directory you are calling solver from, or change the InitialConditions tag to: <F VAR="u,v,w,p" FILE="./base/restart.rst" /> Regarding A. I do not know. Best, Stan On 08/29/2017 01:28 PM, Peltonen Petteri wrote:
For the past weeks I've been testing nektar for incompressible jets and so far I've been able to compile the code on our cluster and to run some simulations with it too. However, I still have a few questions:
A) What is the best way to compute the Reynolds stresses in cylindrical coordinates? In jets, it is common to plot the stresses only as function of the radial coordinate and to average azimuthally (like in pipes). Can the stresses be computed in cylindrical coordinates run time or do I have to save snapshots of 3D-fields to disk and do everything in a post processing step?
B) How do I restart a simulation? So far I haven't succeeded with the following approach: -Run simulation for some time to produce jet.fld. -FieldConvert base/jet.xml base/jet.fld restart.fld -mv restart.fld base/restart.rst -Set initial conditions to: <FUNCTION NAME="InitialConditions"> <F VAR="u,v,w,p" FILE="restart.rst" /> </FUNCTION> -IncNavierStokesSolver base/mesh.xml base/jet.xml (the mesh is in separate .xml file) -->Unable to open file: restart.rst C) What is the difference between .chk and .fld? I have a hunch that the .chk files could be used to restart the simulation with much less effort...
Petteri Peltonen, (M.Sc.) Aalto University, School of Engineering Department of Mechanical Engineering PO Box 14300 FI-00076 Aalto, Finland +358 44 0554984 petteri.peltonen@aalto.fi
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Hi Petteri, Thanks for getting in touch. Here's some brief answers for you: A) We don't have a tool to calculate the stresses in cylindrical coordinates. However I think it is probably possible to convert the stresses analytically from the Cartesian fields without post-processing the individual chk files. B) You should be able to just use the fld or chk files directly without using FieldConvert. i.e.: - Run simulation to produce jet.fld - cp -R jet.fld ../newrun/jet.rst - Use the restart file in the initial conditions function C) There's no difference between chk/fld files, other than chk are written during the simulation and fld are written at the end. Cheers, Dave
On 29 Aug 2017, at 12:28, Peltonen Petteri <petteri.peltonen@aalto.fi> wrote:
For the past weeks I've been testing nektar for incompressible jets and so far I've been able to compile the code on our cluster and to run some simulations with it too. However, I still have a few questions:
A) What is the best way to compute the Reynolds stresses in cylindrical coordinates? In jets, it is common to plot the stresses only as function of the radial coordinate and to average azimuthally (like in pipes). Can the stresses be computed in cylindrical coordinates run time or do I have to save snapshots of 3D-fields to disk and do everything in a post processing step?
B) How do I restart a simulation? So far I haven't succeeded with the following approach: -Run simulation for some time to produce jet.fld. -FieldConvert base/jet.xml base/jet.fld restart.fld -mv restart.fld base/restart.rst -Set initial conditions to: <FUNCTION NAME="InitialConditions"> <F VAR="u,v,w,p" FILE="restart.rst" /> </FUNCTION>
-IncNavierStokesSolver base/mesh.xml base/jet.xml (the mesh is in separate .xml file)
-->Unable to open file: restart.rst
C) What is the difference between .chk and .fld? I have a hunch that the .chk files could be used to restart the simulation with much less effort...
Petteri Peltonen, (M.Sc.) Aalto University, School of Engineering Department of Mechanical Engineering PO Box 14300 FI-00076 Aalto, Finland +358 44 0554984 petteri.peltonen@aalto.fi _______________________________________________ Nektar-users mailing list Nektar-users@imperial.ac.uk https://mailman.ic.ac.uk/mailman/listinfo/nektar-users
participants (3)
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David Moxey
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Peltonen Petteri
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Stanisław Gepner