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

(a) Illustration of spatial-temporal correlation of typical LCS at x₀ = 48.3 mm, Δx = 11.13 mm, ; (b) convection velocities of the LCSs in TBL flows over both surfaces.