[syed]

Thank you fedor for your reply. is this example that you gave is present in current open LB version ? I am searching for this porosity profil3D . But 2 am not able to find it . will you please help.

[syed]

Thank You, Adrian, for such an elaborate response. It will take some time and practice to comprehend the exact work.
As a second idea, I was thinking to implement the attractive force exerted by the wall (1/z^3) as an external force in the descriptor and the boundary will purely bounce back. It is possible? This way I might avoid writing my own post-processor for now, which I will surely write in some time. So do we have any analytical functor where I can add this z-dependent function as an external function to both of my lattices? Just like gravity in the rayleigh instability application.
And secondly, can we add thermal noise to our application? do we have this kind of dynamic also?

[syed]

Dear developers,
I am trying to write the post-processor for the boundary where I wanted to couple the ghost nodes with the nearest fluid with a pseudopotential of F=g(x)Ψ(x)s(x + e)e, where e is the discrete velocity and s(x+e) is 1 if x+e lies on the wall and 0 otherwise. I will substitute a constant for g(x).
So, my plan to implement this boundary is to write a post-processor, just like setFreeEnergyWall. Am I correct? Is this way to add the force F to my lattice points near the wall, and will this force be added to the collision term?
My work plan is as such:
1. Create Descriptor that holds additional fields (external F, velocity, Omega)
2. Prepare geometry (two Slatttices with 1 as fluid and 2 & 3 boundary material)
3. Patching dynamics to the fluid of Slattices (ForcedShanChen)
4. Creating coupling between Slattices (ShanChen pseudopotential)
5. Patching dynamics to boundaries (Upper wall only bounce-back)
6. Patching dynamics to boundaries (Lower wall bounce-back + Force described above)
7. Initialize lattice points with values
8. Collide&Stream
9. communication inter-Slattices
9. Execute coupling of point 4.

Am I correct about the concepts? Adding postprocessor for wall and fluid nodes will add the F values to its dynamics and will be taken care in collide & stream?

[syed]

I can find the one to edit, but can you suggest which one will be better? This will make my task more manageable. Thanking you in advance.

[syed]

Thank you Mathias for your reply. I see that I have to write a post-processor which will be integrated after the streaming process. Do I have to write it from scratch or do we have any such post-processor where I can just manipulate or insert the above-mentioned coupling?

[syed]

I am just thinking of how to couple ForcedShanchen dynamics between fluid and the boundary (different material numbers). I did it for fluid(A)-fluid(B). I want interaction potential between fluid and the boundary of the form = = G*Ψ(x)*s(x + e)e, where s is 1 if (x+e) is a wall boundary node and 0 otherwise.

[syed]

Thank you for your reply. I am still having confusion about the initial density of the system. If I initialize the density of my domain with a particular material number using two Slattices, say Slattice1 (RhoA) and Slattice2 (RhoB) for two components, then the overall density of my system will be the <sum of densities=RhoA+RhoB>, where <> denotes the average from lattice points. Or the density at the lattice point will be the average as <(RhoA+RhoB)/2>.

[syed]

Dear developers, I am confused about what rho0 we are substituting in the forcedshanchengenerator to generate the coupling. This should equal the rho (0.5) I took for fluid component 1. I am confused about the role of rho0 in the coupling generator.

[syed]

Thank you Julius for your reply, and indeed I was looking for options available in OpenLB, like CSV class, to write the data.
And with “metadata” I meant the lattice point’s positions over which the density is defined.
I understand the segmentation fault would have been because of wrong indexing while using the functor.
Do you think the writing data for each lattice point and the lattice point position itself could be possible using the writeData function of the CSV class?
And I want to know where exactly the data is stored, like in what object?

[syed]

Dear Developers, now I am trying to extract data on density from 3D lattices. I know BlockReduction will not work here and extracting data directly from functors will implement an issue with cuboid numbering. How should I proceed here? I want raw data without Paraview.

[syed]

Dear Mathias, I initially used Paraview to visualize the data. But, to carry out analysis relevant to my project I need the raw data. I have my codes to extract results. And also I need ensemble averaging by running the code multiple times and gathering the data for statistical averaging.
I used both ways to create output from the code. I used density functor and tried the () operator which worked fine serially but threw segmentation fault when I ran it parallel. Using block reduction, I got gibberish as I understand it is because of multiple ranks executing the Ofstream object I created.

Can you please guide me regarding the most probable solutions? Is there any way I can extract and write metadata and the data corresponding to the metadata in a file with parallel implementation?

[syed]

Dear developers, I was able to extract the data using the density functor. But, I am facing a problem when I increase the processors for my simulation and supply the same input in the operator () of the functor. If I run the cod in serial then I get the correct density output(output[0],output[1]) for input=(ix,iy). But as I increase the rank, for the same input I get garbage values in the output. And I if I use blockReduction then I am unknown to how the density data is arrayed in the object.

[syed]

Hi @achodankar, I could output the density and the lattice point’s position using the density functor. But, I am having a problem with the input and output array. Things go fine if I don’t use parallelism but as I increase the ranks I do not get correct values for the output. Can you help me out? It seems that I am not providing correct input, as with more ranks the cuboid number becomes a member.

[syed]

Did you solve the problem? I am stuck with the same problem.

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