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Plot over line average magnitude of particle velocity in paraview 

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June 12, 2014, 03:41 
Plot over line average magnitude of particle velocity in paraview

#1 
Senior Member

Hi all,
How can I plot over line the particle velocity in a lagrangian solver? "plot over line" plots the continuous phase variables only and can not plot lagrangian variables. Any idea? 

June 13, 2014, 02:42 
Plot over line average magnitude of particle velocity in paraview

#2 
New Member
Charlie
Join Date: May 2014
Posts: 9
Rep Power: 4 
Hello,
How is possible to plot over line the velocity of particles in lagrangian solvers like MPPICFoam? How can we find the average magnitude of particle velocity in a twohorizontal lines? Thanks in advance 

June 14, 2014, 08:40 

#3 
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Bruno Santos
Join Date: Mar 2009
Location: Lisbon, Portugal
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Greetings to all!
@Maysam: There is a filter named "Plot data" which will plot any dataset. So essentially it depends on whether you can prepare the Lagrangian data in a way that it's ready to be plotted. Best regards, Bruno 

June 14, 2014, 10:24 

#4  
Senior Member

Quote:
I couldn't use this filter. What we need is plotting average of particle velocities in a line. Because the particles are not in a horizontal line and there is some vertical distances, I think we should use averaging in each cell (like calculation of betta in drag force source term) then possible to plot a discrete lagrangian variable over a line. Running tutorials in Lagrangian solvers like MPPICFoam creates Lagrangian velocities (U) in timeFolder/lagrangian/kinematicCloud directory. The problem is they are sorted by their particle ID, not mesh cell number. What do you think about plotting these discrete variables over line using "Plot Data" filter? Regards, 

June 15, 2014, 08:13 

#5 
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Bruno Santos
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Greetings Charlie and Maysam,
Since both your questions are related, I've moved all posts into a single thread. If I understand your questions correctly, you want to:
It looks like that for this particular objective, you will have to create a dedicated OpenFOAM utility or Python filter for ParaView. Problem is that the more I think about this, the less sense it makes to me. Because the problem is that this approach implies binning (placing in bins ) into each mesh cell the average speed of all particles inside that cell. In other words, the plot you'll get will be more of a spacial histogram of the particle velocity along a line. Thinking even further, it seems that you want to calculate the average velocity of particles that are at a certain distance of a line, perhaps using a weighted distance average... OK, the more I think about this, the more questions I end up with. So, what is the specific sampling criteria do you want to use? I ask this because the particles are solved almost separately from the mesh, therefore it doesn't make much sense to plot particle speeds over a line, since very rarely will particles will cross over that line. Best regards, Bruno
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June 15, 2014, 08:40 

#6  
Senior Member

Quote:
Yes I meant these steps exactly. I need particle flux for each grid cell using this equation: particle flux (kg/m2.s)=(1alpha.air)*rho_p*U_p This is the flux of particles in each time. Averaging this term leads to the flux of particles in a desired line. 

June 15, 2014, 11:30 

#7 
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Bruno Santos
Join Date: Mar 2009
Location: Lisbon, Portugal
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Hi Maysam,
The most I can do is to suggest that you study the source code that is in the folders indicated by the following commands: Code:
echo $FOAM_UTILITIES/postProcessing/lagrangian/particleTracks echo $FOAM_SOLVERS/lagrangian/DPMFoam In addition, have a look into this wiki page for more ideas: http://openfoamwiki.net/index.php/Ho..._based_methods Good luck! Best regards, Bruno
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July 24, 2014, 07:55 

#9 
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Matthias Neben
Join Date: Oct 2011
Location: Cottbus (Germany)
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Hello Maysam,
did you find a appropriate solution? I had the same problem and therefore I changed the DPMFoam source code: in createFields I wrote Code:
Info<< "Creating field particleFlux\n" << endl; // mass Flux of the lagrangian particle [kg/(m^2*s)] volVectorField particleFluxByA ( IOobject ( "particleFluxByA", runTime.timeName(), mesh, IOobject::NO_READ, IOobject::AUTO_WRITE ), mesh, dimensionedVector("zero", dimVelocity*dimMass/dimVolume, vector::zero) ); Code:
typedef typename basicKinematicTypeCloud::particleType parcelType; Code:
forAll(particleFluxByA,i) { particleFluxByA[i] = vector(0.0,0.0,0.0); } forAllConstIter(typename basicKinematicTypeCloud, kinematicCloud, iter) { const parcelType& p = iter(); const label cellI = p.cell(); particleFluxByA[cellI]+=p.nParticle()*p.mass()*p.U(); } forAll(mesh.V(),i) { particleFluxByA[i]/=mesh.V()[i]; } The mass averaged mean value can be calculated with Up=sum(vi*mi*ni)/mtotal mtotal =(total) mass of all parcels in a cell; mi, ni and vi are the values of the individual parcels mtotal=rho_bulk*Vcell > f=rho_bulk*sum(vi*mi*ni)/(rho_bulk*Vcell) =sum(vi*mi*ni)/Vcell Kind regards Matthias 

July 24, 2014, 11:46 

#10  
Senior Member

Quote:
I wrote a Fortran code to do postprocessing the results. Your work in changing the source code seems nice. I try yours too and compare it with mine. Regards, 

October 31, 2014, 22:18 

#11  
Senior Member
MultiComb
Join Date: May 2014
Posts: 198
Rep Power: 4 
Quote:
hello,Matthias Neben, how can i get the particle's mean velocity and RMS along a line (a distance tolerance ), i'm really new to OF, any suggestion will be helpful!! regards, wen Quote:
HI,Charlie. Have you solved your problem? please give me some suggestion, thank you ! regards wen Last edited by wyldckat; November 1, 2014 at 08:34. Reason: merged posts, since they were posted an hour apart... and trimmed down the first quote for easier reading 

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