Hum, I do not know if it is the right channel for this : anyone know if a native velocity parabola (Poiseuille flow) is embedded as boundary condition in OF ? Because if I understand this document, one can have this poiseuille profile with uniform pressure boundary condition ? https://www.wolfdynamics.com/wiki/tut_hagen_poiseuille.pdf But considering I want a fixed mass flow, isn't better to code myself a parabola profile like in there ? This is the one I tried btw, for now the profile after t0 is WEIRD, I am guessing a problem in my equation ?