HLBM: particle-particle interaction and fluid-particle momentum exchange

[guojuw]

Dear OpenLB developers:

I am pretty interested in your HLBM method for resolved fluid-particle flow. Let start the discussion with your example code dkt2d and your publication [1].

1. Hydrodynamic force from fluid on particle. If I am correct, the force acting on particle is computed via “void ParticleDynamics3D<T, DESCRIPTOR>::computeBoundaryForce()” in the source file “olb-1.3r1/src/particles/hlbm/hlbmDynamics3D.hh”. I check the code “BlockLatticePorousMomentumLossForce3D<T, DESCRIPTOR>::BlockLatticePorousMomentumLossForce3D()” in source file “olb-1.3r1/src/functors/lattice/blockLatticeLocalF3D.hh”. There is a loop over a particle covered lattice cell to compute the momentum exchange:

// compute momentum exchange force on particle
T tmpForce[3] = {0.,0.,0.};
tmpForce[0] += this->_blockLattice.get(iX, iY, iZ).template getFieldPointer<descriptors::VELOCITY_NUMERATOR>()[0];
tmpForce[1] += this->_blockLattice.get(iX, iY, iZ).template getFieldPointer<descriptors::VELOCITY_NUMERATOR>()[1];
tmpForce[2] += this->_blockLattice.get(iX, iY, iZ).template getFieldPointer<descriptors::VELOCITY_NUMERATOR>()[2];

I know the code is summing the numerator (Ref. [1], equation below Eq. 6) to recover the hydrodynamic force. From Ref. [1], the hydrodynamic force is computed from Eq. 7. The problem is, how does the numerator related to the bounce-back equation (equation above Eq. 7 from Ref. [1]), how it is implemented in OpenLB code?

2. Particle-particle interaction. I talked to Dr. Krause. The code now is limited to hard sphere collision. I am fine with that. But how is it implement in HLBM? I did a test. When two particle is in contact. The numerator is contacted zone is very high, so the particle can separate. My question is how is the numerator is related to particle collision?

Thanks a lot. I am developing a particle-flow model that may discuss latter.

Regards,
Junwei Guo (PhD candidate)

[1] Krause, M. J.; Klemens, F.; Henn, T.; Trunk, R. & Nirschl, H.
Particle flow simulations with homogenised lattice Boltzmann methods
Particuology, Elsevier, 2017, 34, 1–13

[Nicolas]

Dear Junwei Guo,

after intruducing HLBM to OpenLB in 2017 there have been various minor, but also some major changes, including the momentum exchange algorithm. A lot of them are documented in a more recent publication on HLBM and the OpenLB user guide. You are strongly advised to contemplate both. Another more up-to-date publication is being worked on at the moment, however no specific date for it can be given for now. Here, some further changes to the algorithm will be discussed, which will eventually be part of our next release, which is scheduled for the end of this very month. In case you are looking for the greatest consistency between publications and the implementation, you might need to await the upcoming release and our next HLBM related publication. Another option is of course to attend our next OpenLB spring school, which will give you the opportunity to talk with the developers directly.
I hope, this is of any help for now.

Best,
Nicolas

[guojuw]

Dear Nicolas,

I am looking forward to attending the next OpenLB spring school. That would happen next year. Can you please contact the developers to solve this problem?

Thanks again.
Regards,
Junwei GUo

[Author]

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