S0506-3-1 Sustaining Mechanism of large-Scale Structure in a Turbulent Poiseuille Flow at Low-Reynolds Number

Abstract

Direct numerical simulations of spectral method are performed to study the sustenance mechanism of large-scale structure in relaminarizing channel flow at a very low-Reynolds number. At a low-Reynolds number, the quasi-laminar and turbulent regions simultaneously appear and form the stripe pattern. The turbulent region is flanked by high- and low-speed fluids, which appear upstream and downstream of the turbulent region. The interface between quasi-laminar and turbulent regions features not only the intrusion of high-speed fluids into the downstream side, but also by redirection of streamwise velocity to the spanwise velocity. Thus, generated spanwise velocity becomes driving force for large-scale upward and downward flows which tilts the mean shear in the spanwise direction and contributes to generation and sustenance of the stripe pattern.