Sampling scalar Fields on a surface over time

shock77 · April 1, 2021, 16:26

Hi,

I have created a couple of faceZones to sample pressure and temperature over time (area averaged). Unfortunately they are volume fields and areaAverage doenst work with those. So first I have to interpolate the volume fields onto the faceZone. I am not able to run the surfaceInterpolate utility and cant find a tutorial or an example.

Did anyone face this problem and can show me an example? Is there a better solution for this problem? I am using openfoam4.1.

KTG · April 1, 2021, 19:51

Are you sure you want/need the values at the face zones? What boundary conditions are you using? If they are zeroGradient, it should be sufficient to grab the values at the cell centers adjacent to the patches I think. If that would work for you, you should be able to make a cellSet from the face set in your topoSet, and then just sample it.

Hope it helps -

shock77 · April 2, 2021, 06:08

Hi and thanks for your reply.

Actually the faceZone is not a boundary, but a faceZone inside a pipe. I am sampling the mass flux at this faceZone. Additionally I would like to sample the area averaged pressure and temperature at this faceZone. Obviously I could create a cellZone with the thickness of 1 cell and use that instead. Just want to know if there is a clever way how to do it with a faceZone.

KTG · April 2, 2021, 16:09

Its not elegant, but one possible workaround would be to export the face centers to text, and then use the sampleFields function object on those points, which would allow you to choose whatever interpolation scheme you want.

shock77 · April 7, 2021, 06:32

How exactly can I export the faceCenters to text? What do you mean?

KTG · April 7, 2021, 17:27

If you don't mind doing a little programming I think you can get the cell centers with:

const surfaceVectorField& Cf = mesh.Cf();

Here is a thread where they implemented somthing like that:

How to export patch face centre Coordinate during sampling ?

I feel like there should be a simpler way to do this, but I am not sure what is it. You can veiw the faceSet in paraview, but there is no cell center info there. Maybe you can find a way to generate it though.

shock77 · April 8, 2021, 04:23

Hm I actually dont mind programming, but I dont think its worth the effort.
I also think there must be some easiert way and its seems strange that I cant find one. Thanks anyway for your kind help!

April 1, 2021, 16:26	Sampling scalar Fields on a surface over time	#1
shock77 Senior Member Join Date: Dec 2019 Posts: 215 Rep Power: 7	Hi, I have created a couple of faceZones to sample pressure and temperature over time (area averaged). Unfortunately they are volume fields and areaAverage doenst work with those. So first I have to interpolate the volume fields onto the faceZone. I am not able to run the surfaceInterpolate utility and cant find a tutorial or an example. Did anyone face this problem and can show me an example? Is there a better solution for this problem? I am using openfoam4.1.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
courant number increases to rather large values	6863523	OpenFOAM Running, Solving & CFD	22	July 5, 2023 23:48
laplacianFoam with source term	Herwig	OpenFOAM Running, Solving & CFD	17	November 19, 2019 13:47
pressure in incompressible solvers e.g. simpleFoam	chrizzl	OpenFOAM Running, Solving & CFD	13	March 28, 2017 05:49
Issue symmetryPlane 2.5d extruded airfoil simulation	281419	OpenFOAM Running, Solving & CFD	5	November 28, 2015 13:09
compressible flow in turbocharger	riesotto	OpenFOAM	50	May 26, 2014 01:47

April 1, 2021, 19:51		#2
KTG Senior Member Abe Join Date: May 2016 Posts: 119 Rep Power: 9	Are you sure you want/need the values at the face zones? What boundary conditions are you using? If they are zeroGradient, it should be sufficient to grab the values at the cell centers adjacent to the patches I think. If that would work for you, you should be able to make a cellSet from the face set in your topoSet, and then just sample it. Hope it helps -

April 2, 2021, 06:08		#3
shock77 Senior Member Join Date: Dec 2019 Posts: 215 Rep Power: 7	Hi and thanks for your reply. Actually the faceZone is not a boundary, but a faceZone inside a pipe. I am sampling the mass flux at this faceZone. Additionally I would like to sample the area averaged pressure and temperature at this faceZone. Obviously I could create a cellZone with the thickness of 1 cell and use that instead. Just want to know if there is a clever way how to do it with a faceZone.

April 2, 2021, 16:09		#4
KTG Senior Member Abe Join Date: May 2016 Posts: 119 Rep Power: 9	Its not elegant, but one possible workaround would be to export the face centers to text, and then use the sampleFields function object on those points, which would allow you to choose whatever interpolation scheme you want.

April 7, 2021, 06:32		#5
shock77 Senior Member Join Date: Dec 2019 Posts: 215 Rep Power: 7	How exactly can I export the faceCenters to text? What do you mean?

April 7, 2021, 17:27		#6
KTG Senior Member Abe Join Date: May 2016 Posts: 119 Rep Power: 9	If you don't mind doing a little programming I think you can get the cell centers with: const surfaceVectorField& Cf = mesh.Cf(); Here is a thread where they implemented somthing like that: How to export patch face centre Coordinate during sampling ? I feel like there should be a simpler way to do this, but I am not sure what is it. You can veiw the faceSet in paraview, but there is no cell center info there. Maybe you can find a way to generate it though.

April 8, 2021, 04:23		#7
shock77 Senior Member Join Date: Dec 2019 Posts: 215 Rep Power: 7	Hm I actually dont mind programming, but I dont think its worth the effort. I also think there must be some easiert way and its seems strange that I cant find one. Thanks anyway for your kind help!