OpenLB – Open Source Lattice Boltzmann Code › Forums › on OpenLB › General Topics › Outflow of Cylinder3d › Reply To: Outflow of Cylinder3d March 21, 2022 at 10:03 am #6390 johannaParticipant Dear Xu Yang, i would suggest to try the setZeroDistributionBoundary which sets every population with direction into the bulk to zero. I hope this fits to your application case. Yours sincerely, Johanna