Hi Fabian, you can actually run in verbose mode ./executable -v file.xml to see additional parameters, such as the operator evaluation. Regarding the most appropriate hp space, this depends on the case. For the Nan, I would suggest that you try to increase the number of quadrature points while keeping the number of modes fixed. A second possibility is that you start the simulation non-impulsively but using a ramp in time for the farfield boundary conditions. Regards, Gianmarco Gianmarco Mengaldo Department of Aeronautics and Mathematics Imperial College London South Kensington Campus SW7 2AZ, London, UK ***Currently at Caltech From: "Selbach, Fabian" <fabian.selbach@student.uni-siegen.de<mailto:fabian.selbach@student.uni-siegen.de>> Subject: [Nektar-users] Default operator evaluation in Nektar++ and error "NaN found during time integration" Date: 10 October 2016 at 14:09:28 BST To: "nektar-users@imperial.ac.uk<mailto:nektar-users@imperial.ac.uk>" <nektar-users@imperial.ac.uk<mailto:nektar-users@imperial.ac.uk>> Dear Nektar++ -Community, please can you tell me the default operator evaluation in Nektar++? In the papers "From h to p efficiently" there are mentioned three kind of types: 1. global matrix approach 2. local matrix approach 3. sum-factorization I want to choose the best hp/ configuration for my 3D simulation and this -of course- depends on the operator evaluation strategy. I think actually Nektar++ uses the global matrix approach by default, but I'm not sure by 100%. My second question depends on the error message: "Fatal : Level 0 assertion violation NaN found during time integration." While using this configuration: ======================================================================= EquationType: EulerCFE Session Name: 3Dmeshcube_h10 Spatial Dim.: 3 Max SEM Exp. Order: 3 Num. Processes: 24 Expansion Dim.: 3 Riemann Solver: HLLC Advection Type: Projection Type: Discontinuous Galerkin Diffusion Type: Advection: explicit AdvectionType: WeakDG Diffusion: explicit Time Step: 0.01 No. of Steps: 10000 Checkpoints (steps): 1000 Integration Type: RungeKutta2_ImprovedEuler Problem Type: General ======================================================================= Initial Conditions: - Field rho: rhoInf + (0.01 * exp(-0.077*(x^2 + y^2 + z^2))) - Field rhou: rhoInf * uInf - Field rhov: rhoInf * vInf - Field rhow: rhoInf * wInf - Field E: (pInf / (Gamma - 1)) + ((rhoInf/2) * uInf^2) + ((0.01/(Gamma-1))*exp(-0.077*(x^2 + y^2 + z^2))) +( (0.01/2) * uInf^2 * exp(-0.077*(x^2 + y^2 + z^2))) I already changed my time-step and the refinement of my mesh and i think this error message is because of oscillation of my solution. So maybe my mesh is not fine enough or i must increase p. But i want to use a fix h to p constellation to test the efficiency. Can anybody help me with this problem? I already tried to use the spectral hp dealiasing, the smooth advection and artificial viscosity, but it doesn't worked or helped... Thanks for any answer. Best regards Fabian _______________________________________________ Nektar-users mailing list Nektar-users@imperial.ac.uk<mailto:Nektar-users@imperial.ac.uk> https://mailman.ic.ac.uk/mailman/listinfo/nektar-users