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• #6817
Jijo
Participant

I am new to the LBM and I am interested in microencapsulated PCM. I tried to simulate the Galliummelting2d and Stefanmeltin2d examples and I have a couple of questions I would like to ask.

1. In the galliummelting2d example, Why is the value of the specific heat and density set to 1? as shown below:

const T cp_s = 1.0; // J / kg K
const T cp_l = 1.0; // J / kg K
—–
const T density = 1.
—–

2. If I try to implement the thermophysical properties of paraffin onto the Stefanmelting2d example, the code runs but the time step is stuck at 0 forever.

I would appreciate it if anyone could answer me.
Thanks,

#6825
mathias
Keymaster

Dear Anas,

what is the resolution (dx, dt) and the number of cores you are using. What is number of time lattice time steps? Maybe in your physical setup the output interval is too large, i.e. the number of lattice time step is too big. In that case you could output a smaller interval.

Best
Mathias

#6826
Jijo
Participant

Dear Mathias,

Physdelta T is 6 seconds and Physdelta x is 0.002.If I use specific heat capacity for liquid and solid as 2400 and 1926 rather than the original code which is 1 and 1, the values (lattice velocity and Tau) sky rocket.

My setup is operating at 4 cores.

You are correct the the interval is too large because melting the PCM takes alot of time.

The time step increases each time 5000.

#6830
mathias
Keymaster

So, choose a smaller time interval for the output and consider to use much more core since you are in a real world setup. So maybe for 2D ~100 of cores and for 3D ~1000 or GPU clusters.

Best
Mathias

#7151
Mike
Participant

Hello everyone,

I also wonder why pcm specific heat is set as 1, which I think it should be set as converter.getLatticeSpecificHeatCapacity(physSpecificHeatCapacity), it will be much appreciated if anyone can help solve this!

Best
Mike

#7153
mathias
Keymaster

I guess that was done as in the original benchmark, see the references in https://www.sciencedirect.com/science/article/abs/pii/S0017931019361927 . Best Mathias

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