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) Contour plot of the eigenmode of the leading-order ith POD mode over test plates. From top to bottom: the 1 st, the 5 th, the 10 th, and the 15 th (left: smooth; right: riblets).