pressure boundary condtion and an external force in collsion part

I meet over a problem wheter is the pressure boundary condition and an external force in collision part used in LBM, namely if used pressure boundary condition , did not use an external force or body force in collision part, or on the contray.

Can you be a bit more specific?

I use Guozhaoli’ non-equilibrium extrapolation method for the pressure boundary condtions in the inlet and outlet.
In the collision step, i add a additional force term in collision equation. additional force term is Guozhaoli’ method.
I found the simulating solutions were lagrer than the analytical ones with additional force terms, on the contray, were smaller than the analytical ones without additional force terms.


do you take into account that the physical velocity has to be corrected by half of the force applied during that time step?
This point is discussed in Guo’s paper.



I use the period boundary condtion and the standard bounceback method,and gain correct solutions with the analytical solutions.