Viscous dissipation model for fast vortex method in simulation of decaying turbulence

For realistic turbulent flow simulation, quantitative representation of turbulent flow dynamics is desired. In the present study, two-dimensional homogeneous isotropic turbulence is simulated by using grid-free vortex method to focus on the viscous dissipation process. The results are compared with those of spectral DNS. Two viscous diffusion models, i.e., core spreading model and Moving Particle Semi-implicit (MPS) Laplacian model, are compared. For the former model, marge and addition process are incorporated to ensure uniform distribution of vortex elements. It is shown that the MPS Laplacian model is superior to the conventional core spreading model in terms of the decay rate of enstrophy and energy spectra. Computational time is remarkably reduced by using Fast Multipole Method (FMM) while retaining accuracy.