OpenLB – Open Source Lattice Boltzmann Code › Forums › on OpenLB › General Topics › [SuperVTMwriter3D] Error: could not open file › Reply To: [SuperVTMwriter3D] Error: could not open file October 22, 2021 at 3:13 pm #6086 AdrianKeymaster Some questions in order to pin this down: Does it work without the cylinder size change? Did you call vtmWriter.createMasterFile as in the default poiseuille3d case? Do the target folders exist and have the correct permissions?