hi all, I'm running coarse simulations of fully (not quasi) 3D Taylor-Green vortex case at Re=1600 using SVV in IncNavierStokesSolver. The domain is [-2pi,2pi]^3 with elemental grid 16^3 and NumModes=5 (giving me 64 solution points per direction). The case is defined in the tutorials at: http://doc.nektar.info/tutorials/latest/incns/taylor-green-vortex/incns-tayl... I'd like to ask the users a typical working maximum dt or CFL for similar flows with NumModes=5. I could not run the simulation for less than normalised dt=1e-3 which corresponds to: CFL = V0*delT/delX, = 1*1e-3/(2pi/64) ~ 0.01 I tried to run the tutorials (at the link above) with 16^2 grid with NumModes=5 and homogeneous third direction. I could run the simulation up to dt=20e-3. Thus, maximum working dt for fully 3D simulation is at least 20 times smaller. There may be a problem with the boundary since the numerical instability starts at the periodic boundary normal to z-direction. I'm attaching the fully 3D set-up being used. kindly have a look and let me know if I am missing something. Cheers, Vishal