I am writing a 2D pseudo spectral code for turbulence in a box with 1024 grid points with 3/2 aliasing scheme in the vorticity/stream function formulation. the vortices tends to appear very slowly and energy is decaying faster than expected at a Reynolds number of 5*10^4. The faster decay in energy leads to very slow vortices (which is not the case) I am not sure where the problem is. Any help in this would be useful. I have tried different initial conditions like random velocity and gaussian white noise but nothing seems to work.
Turbulence Pseudospectral Code
navier stokes