INSTABILITY OF LOW-SPEED STREAKS LEADING TOWALL TURBULENCE

摘要: Nonlinear development of streak instability modes is examined up to the turbulent stage experimentally through artificially producing spanwise-periodic low-speed streaks in a laminar boundary layer. The experiment focused on subhar- monic sinuous mode instability. sinusoidal motion caused by maintained three or four wavelengths down- stream beyond nonlinear saturation instability, and subsequently breaks down. After breakdown, near-wall with lateral spacing 100 wall units newly develop, mean velocity profile starts exhibit log-law. It also found that interaction between quasi- streamwise vortices developing along neighboring causes large-scale arch-like develop region away from wall.