Abstract
The direct numerical simulation (DNS) of the turbulent channel flows by the sudden changes of the Reynolds number (Re) is performed to investigate the transient phenomena in the turbulence field. In the first stage of the transient state, the wall friction changes to unit during a very short time. Then again that is recovered about 10% in the second stage and the profiles of the mean quantities asymptotically reach to the fully-developed ones. At the case of the sudden Re increase, the low-speed streaks are weakened, while at the inverse case those are enlarged temporarily in the transient state.
