Description of Research Area

Large-Scale DNS Study on Laminar-Turbulent Patterning in Subcritical Wall Turbulence

Research Subject

With respect to a non-equilibrium critical phenomenon seen in the subcritical transition between laminar and turbulent states, we aim to characterize the turbulent transition process as a directed percolation (DP) universality class by determining the universal properties of the DP transition. We focus on the subcritical transitional regime of a turbulent channel flow between two parallel plates, in which the spatial degrees of freedom in two directions. At the transitional Reynolds numbers, we often encounter large-scale patterning of localized turbulence, for instance, a turbulent stripe shown in figure. To get its overall picture globally, we will perform the world's largest simulation of the channel flow, determine universal laws as a DP class, and explore the mechanism of macro pattern formation. This also aims to build a DP model and to determine the critical Reynolds number of global stability. This study deals with a "synergy" of micro-fluctuation “turbulent fine-scale eddies” and macro-structure "turbulent stripe".