[atul1018]

Hello All,


I am simulating the particle-laden BFS using DPMFoam. The flow conditions are turbulent. I am using RANS simulation with komegaSST model to solve the flow field. I want to extract the forces acting on each particles during each or several times steps.



Any idea, how can I get it. I saw function objects, which is generally defined in controlDict to calculate the forces. But It can only be applied of continuous field (volumetric field) not on lagrangian fields.


Best Regards
Atul Jaiswal

[oswald]

Dear Atul,


afaik the values of single specific forces are only available within the specific force calculation and more or less simply summed up in the particle class. Thus, when I wanted to have access to these values, I wrote some code inside each force to output the force value at the desired time steps in a single output file for each force.


There is a concept similar to functionObjects for lagrangian stuff, namely cloudFunctionObjects, but I think that they can't access single force values.


Best,
oswald

[atul1018]

Dear Oswal,


Thanks again for you answer to my threads.


It means that you modified the source codes of each forces and wrote there to give output of the values. For example, if I want to get output of each time step for gravity force, you modified the library intermediate/submodels/kinematic/particleForces/Drag and recompiled the solver e.g. DPMFoam with modified drag force source code?


Yes, cloudFuctionObject seems not to be right tool to get individual forces acting on particles.



Thanks and Best Regards
Atul Jaiswal

[oswald]

Exactly, I modified the source files for each single force I wanted to output. There might be more elegant solutions, but it was sufficient for me. I don't have access to the code I wrote, but if you are interested I can try to find it.



I don't think that it is possible to use a cloudFunctionObject for this at the moment without changing other things inside the forces' source code.

[atul1018]

Dear Oswald,


It would be nice if you can find the codes, I would be great help for me. I can understand that you are busy, please take your time and send me when you get it.


Best Regards
Atul

[Shah Akib Sarwar]

Can any one of you help me with how to output drag forces on particles at each time step?

[oswald]

I think you need to implement some output functionality in either the source code of the actual force(s) you are interested in or in the code of "particleForceList.C", inside the loop over all the forces.

[Shah Akib Sarwar]

Thank you for your reply. Could you provide any guidance/example on how to do these for SphereDrag?

[oswald]

The easiest way in my opinion (not the best, though) would be to just add some additional output in SphereDrag.C. There is a function called "calcCoupled". Here you could change

    return forceSuSp(Zero, mass*0.75*muc*CdRe(Re)/(p.rho()*sqr(p.d())));

to something like

    forceSuSp drag = (Zero, mass*0.75*muc*CdRe(Re)/(p.rho()*sqr(p.d())));
    Info<< "PID: " << p.origId() << " | Current force: " << drag.second() << endl;
    return drag;