Abstract
DNSs with a spectral method are performed to study Couette as well as Poiseuille flows at a low-Reynolds number. In both flows, quasi-laminar and turbulent regions simultaneously appear in unique stripe pattern over a computational region, and especially, the turbulent regions, tilted about 20〜30 degrees from streamwise direction, are flanked by high-speed fluids at the upwind side and low-speed fluids at downwind side. As a result of calculating the budget of turbulent energy inside the turbulent region, it is found that in the upwind side, the enhanced sweep contributes to transferring turbulent kinetic energy into the wall vicinity, while in the downwind side where the sweep dominance disappears, its transfer into the wall vicinity is significantly attenuated, and turbulent kinetic energy is mostly transferred into the channel center.
