Abstract
Direct numerical simulation (DNS) of decaying isotropic turbulence with a passive scalar, say temperature, has been done on 5123 grids of the Numerical Wind Tunnel at National Aerospace Laboratory. The fields of vorticity and temperature gradient are visualized to clarify the process of formation of their local structures such as “worms” and sheets. We show that the circulation around a worm is close to that around a Burgers vortex even though the former is very far from the latter in detailed structure. The self-similar structures of energy dissipation and scalar dissipation in our DNS are visualized for intuitive understanding. It is found that the multifractal structure of energy dissipation is almost invariant in the process of decay. The joint multifractal of energy and scalar dissipations is established on the DNS basis.
