Direct numerical simulation of subcritical wall turbulence using very large aspect-ratio domain¶
Takahiro Tsukahara (Tokyo Univ. of Sci.)
Abstract¶
We studied the subcritical transition of wall-bounded turbulent shear flows including plane-Poiseuille, duct, and annular-Couette flows near the global critical Reynolds, by means of DNS (direct numerical simulation without any turbulence model) with an aid of SX-series supercomputers. A very large aspect-ratio domain allows us to detect global features of the spatio-temporal intermittency with turbulent band/stripe and similarity to a DP (directed percolation) universality-class phenomenon, which exhibits very long correlation lengths. For instance, a new DP phenomenon was found in artificially-extended annular system with azimuthal domain larger than 2π. Further DNS study using large aspect-ratio domain is required to precisely measure the DP exponents and would unravel the universality of subcritical transitions.