Dear Nektar++ developers/users, We're encountering some difficulties with the compressible flow solver of Nektar++. We're trying to replicate a laminar flat plate case from SU2 (https://su2code.github.io/tutorials/Laminar_Flat_Plate/) where the free-stream Mach is 0.2 and with a rather high unit Reynolds number of 4.2 million. The structured mesh was generated with Gmsh, we impose a Blasius profile at the inlet and a similarity solution as the initial condition. This results in a transient wavepacket advected downstream with the iterations. To get the simulation running, we had to resort to using a very small time step (1e-8) but it still blows up after a certain number of iterations. You can find attached a screenshot of the last flow field (u,v) saved as well as our XML parameter file. We read carefully the user guide and went through the different threads of the mailing list, with some questions: - is it hopeless to try and solve such a high Reynolds number, regardless of the mesh resolution? Is it likely we're suffering from a under-resolution issue? - are there any other parameters implemented recently in the master branch that we could change? The compressible flow solver section of the user guide is not really verbose and for example, we found out about the PressureOutflowNonReflective b.c. Our XML file was set up with some inspiration from the 3D hump of De Grazia. - are there any sponge layers implemented for the compressible flow solver? - we noticed there is a CompressibleBL.cpp source file in the Utilities folder, could it be useful to compute straight away a similarity solution? What was the original purpose of that source file? We'd appreciate if you could notify us of anything suspicious in our XML file. Thank you for your support, Thibaut Appel PhD Student Virtual Product Engineering, Airbus CR&T Department of Mathematics, Imperial College London