New to LBM and OpenLB? Attend our upcoming one-week hands-on Spring School in Marseille/France from 19.05.2025 – 23.05.2025. OpenLB – Open Source Lattice Boltzmann Code › Forums › on OpenLB › General Topics › External force in periodical boundary conditions › Re: External force in periodical boundary conditions January 3, 2019 at 8:12 pm #2994 mathiasKeymaster Please use the indicator interface, see e.g. the poiseuille example.