**3.4. Leading-edge serrations**

A passive flow control method entitled as leading-edge serration as shown in **Figure 7** [43, 44] is inspired by the morphology of humpback whales [45]. This bioinspired technique has recently been investigated for different purposes experimentally or numerically. Wang and Zhuang [46] designed a modified wind turbine blades with sinusoidal wave serrations employed on the leading edge to control the boundary layer separation. Their numerical results indicated that the leading-edge serration suppressed the flow separation with the generation of the counterrotating vortex pairs, especially at high AoA. Cai et al. [47] also numerically investigated a modified airfoil with a single leading-edge protuberance at low Reynolds number. The results showed that the stall angle reduced at the modified airfoil. Furthermore, the pre-stall performance of the modified airfoil decreased, whereas post-stall characteristics were increased. Moreover, an experimental study performed by Wei et al. [48] expressed the hydrodynamic

**Figure 6.** Representation sketch of the flow vane [19].

characteristics of hydrofoils with leading-edge tubercles at Reynolds number of 1.4 × 104 . Their visualization results based on particle tracking revealed that the effects of flow separation were declined with the use of leading-edge tubercles.
