Mass increase with Zou/He?

Lattice Boltzmann Method LBM: Theory
#1

Hi to all,

I am currently implementing Zou/He boundary conditions. Everything seems to work fine, but I notice mass increase over time, for example when imposing a Poisseuille profile on in- and outlet of a pipe. The rate depends on the given velocity, but is of the order of 0.1% per 1000 timesteps. It happens in my D3Q19 code as well as in the D2Q9 code presented on this page. I got around it by setting rho=1 instead of calculating the density from the incoming populations on the inlet, but this can’t be the best way to do it I assume?

#2

Hi
I think that this[/url] and [url=http://www.lbmethod.org/community:avoid_mass_increase_with_pressure_outlet]this will help you.

To sum up, if you impose the velocity on the inlet and a constant density on the outlet, the average density of the lattice is bounded.

#3

Thank you, that is exactly what I was looking for!