Coherent structures over riblets in turbulent boundary layer studied by combining time-resolved particle image velocimetry (TRPIV), proper orthogonal decomposition (POD), and finite-time Lyapunov exponent (FTLE)

Li Shan¹, Jiang Nan^{1, †}, Yang Shaoqiong^{1, ‡}, Huang Yongxiang², Wu Yanhua³

(color online) (a) Mean velocity (u⁺) profiles normalized by the wall units in the TBL flows over both surfaces. (b) Turbulence intensities and Reynolds stress profiles in the TBLs over both surfaces. Upper curve, u_rms/u_τ; lower curve, ; middle curve, v_rms/u_τ.