OpenLB – Open Source Lattice Boltzmann Code › Forums › on OpenLB › General Topics › Claculate Force Term in OpenLB (rayleigh benard problem) › Reply To: Claculate Force Term in OpenLB (rayleigh benard problem) August 4, 2022 at 5:26 pm #6753 navidkyoParticipant Hello Mathias, This is the RayleighBernard2D example of OpenLB V1.4. Material 4 is defined to implement a perturbation; it is not inflow or outflow. I will redefine material 4 and let you know if the error is resolved.