56 巻 (1990) 522 号 p. 351-359
A simple model for turbulence eddy hierarchy was proposed to describe the Kolomogorov's local similarity theory in connection with the characteristic time and eddy scales of turbulence. In weakly anisotropic turbulence, the energy fraction of locally isotropic eddies to the whole turbulence energy increased downstream and exceeded 60% of the total energy at X/M=50 for Reλ=460. Most of the energy dissipation occurred in the quasi-equilibrium wave number range. The strong turbulence became quasi-self-similar and the turbulence Reynolds numbers were kept constant for X/M >65, where the time scale of the decay of turbulence energy became greater than 4∼8 times as large as the characteristic time scale of the energy-containing eddy at the initial stage of the decay. The strong turbulence was confirmed to be capable of offering an ideal test field for practical large-scale turbulence phenomena.