Dear all,
I am trying to implement the Zou/He BC in my LBM code. The problem is that the results that I obtain are only OK if I use the BGK SRT collision operator or alternatively the MRT with all relaxation parameters equal to (1/tau). If the MRT model with different relaxation values is used the results are not so OK. (By the way, I know that my results are OK because I am solving a Poiseuille flow, which is an analytical solution of LBM, so I should always obtain machine accuracy results, as I obtain for SRT models).
The problem suggests me that the Zou/He BCs proposed originally for SRT model cannot be applied in their original form for a MRT collision model.
In my opinion this is due to the form of the non-equilibrium bounce-back assumption. Maybe the computation of the unknown distribution functions has to be performed in moment space… However, this does not make much sense to me. Does anyone ever notice the same thing? How to solve this?
Thanks in advance for the help
Goncalo