07. Turbulence and Flow Instabilities

Global and local dissipation scaling is evaluated using a DNS (direct numerical simulation) database of temporally developing grid turbulence. The Reynolds numbers based on the grid mesh size are 10,000 and 20,000. First, we obtain the dissipation scaling law using the whole computational region, which is defined as the global statistics. Second, we obtain the dissipation scaling law in the local cubic subdomains. Each subdomain has a side length equal to the integral length scale of the whole computational region. The results show that while the equilibrium law (i.e., constant dimensionless dissipation rate of turbulent kinetic energy, Ce) holds in the global region, the nonequilibrium law, where Ce is not constant and depends on the local Taylor Reynolds number and the global Reynolds number (which depends on the initial conditions), holds in the local subdomains. The results obtained in the local subdomains align with the nonequilibrium scaling law for the global statistics proposed in previous studies.