Restricted nonlinear model for high- and low-drag events in plane channel flow

摘要: A restricted nonlinear (RNL) model, obtained by partitioning the state variables into streamwise-averaged quantities and superimposed perturbations, is used in order to track exact coherent plane channel flow investigated Toh & Itano ( J. Fluid Mech. , vol. 481, 2003, pp. 67–76). When restricting nonlinearities quadratic interaction of fluctuating part component, it shown that structure its dynamics closely match results from direct numerical simulation (DNS), even if only a single streamwise Fourier mode retained. In particular, both solutions exhibit long quiescent phases, spanwise shifts bursting events. It also dynamical trajectory passes close equilibria either low- or high-drag states. statistics are collected at times where friction velocity peaks, mean root-mean-square profiles show essential features wall turbulence DNS for same Reynolds number. For low-drag events, related universal asymptotic called maximum drag reduction (Xi Graham, Phys. Rev. Lett. vol. 108, 2012, 028301). Hence, intermittent nature self-sustaining processes buffer layer contained RNL organized two states plus an turbulent-like attractor. We address how turbulent approaches these exploiting database associated with larger domain.