Dear All, We want to use Nektar++ to perform DNS of blood flow inside constricted vessels. Unfortunately the learning process turned out to be quite slow. We started with the following simple laminar pipe flow problem Diameter = 0.2 m Length = 8 m Kin. viscosity = 2 (10^-3) m2/s Inlet velocity = 1m/s Outlet pressure = 0 Pa Re = 100 Fully developed centerline velocity is known to be 2 m/s. With a fine enough mesh we expect to get this value exactly. But the best we got was 1.974 m/s. We generated the mesh using Gmsh and we suspect that the problem might be related to the curved edge definitions. In the process we observed quite bizarre behaviors, such as even worse centerline velocities as the polynomial order inside the elements is increased. That's why my student Kamil previously asked here couple of questions about this, but I guess some questions remained unanswered or maybe we couldn't interpret the answers properly. To make sure that we're doing everything else right, we generated a similar duct flow problem with straight surfaces. Fully developed centerline velocity is again known and we can easily get that value correct up to 3-4 digits. At this point we're not sure about what we're doing wrong in the pipe flow case. Is it really a curvature issue or something else? We'd really appreciate if you can shed some light. We can share the XML file if that might help to resolve the problem. Thanks in advance for the help and thanks for sharing this flow solver with us. Cuneyt Sert