OpenLB – Open Source Lattice Boltzmann Code › Forums › on OpenLB › General Topics › Mass flux calculation › Reply To: Mass flux calculation March 24, 2022 at 11:10 am #6395 antoniowuParticipant Hi Adrian, Just so you know. I changed my normal from (0,1) to (0,-1) but I am still getting negative mass flux… Regards, Antonio