## 1 Introduction  
By virtue of smaller size and lower speed (<15 cm, 10-20 m/s [1]), Micro Air Vehicles (MAVs) are more portable, more covert, and quieter. Consequently, they have extensive applications in both military and civilian contexts [2; 3]. In comparison to rotary-wing and flapping-wing configurations, fixed-wing MAVs, characterized by their higher lift-drag ratios, offer the greatest endurance [4] for a given mass. However, fixed-wing MAVs often operate within low Reynolds number flow regimes, where flow is predominantly governed by viscous drag, leading to a substantial depletion of propulsion energy. To mitigate drag and enhance airfoil performance, researchers have undertaken extensive investigations from both active and passive control perspectives. These techniques include plasma actuation [5; 6; 7], drag-reducing riblets [8; 9; 10], flexible wings [11; 12; 13], and airfoil optimization [14; 15; 16]. Although having been proven effective in controlling the flow of airfoils, most of these techniques are still not perfect in reducing the viscous drag of small-scale airfoils owing to complicated structures, extra energy cost, or shortage of drag reduction ability. At present, the mainstream research direction in improving the aerodynamic performance of MAVs is focused on airfoil shape, such as directly modifying individual geometric parameters of the airfoil or changing the profile through machine learning and other means. For example, [PERSON] et al. [17] modified the chord length of the airfoil to suppress the generation of separation bubbles at low Reynolds numbers. [PERSON] et al. [18] systematically studied the influence of leading-edge geometry on the flight performance of micro air vehicles through wind tunnel tests and made optimizations. [PERSON] et al. [19] used machine learning to obtain the optimal configuration of two airfoils placed in series in the incoming flow, and [PERSON] et al. [20] directly optimized the geometric shape of the airfoil using genetic algorithms. However, these methods can only target specific airfoils and have a long research period. In contrast, the modeling method [21; 22] can quickly be designed for different working conditions. Then, to develop modeling flow control techniques characterized by a simple structure, low cost, and strong ability of drag reduction seems essential to improve the aerodynamic performance of MAVs airfoils. Characterized by a simple structure and low manufacturing cost, transverse grooves have been proven efficient in reducing the drag near a solid surface. Transverse grooves represent surface structures that are recessed into the wall and extend perpendicularly to the mainstream flow. Their shapes mimic the occurring dunes found in low-entropy forms in the natural world, typically adopting a V-shape [23]. NASA has proposed the \"Micro-Air Bearings\" theory (MABS) to elucidate the drag reduction mechanism of this approach [24], such as in Figure 1. In this theory, the stable boundary vortices generated in the grooves act analogously to bearings, rotating and replacing the friction between fluid and the wall with that of the fluid and vortex to reduce viscous drag. Moreover, NASA [24] also pointed out that low-speed flow near the wall will stagnate on the windward side of the groove head and separate on the leeward side (Figure 1, right), resulting in pressure drag. Finally, the drag reduction effect of the transverse groove depends on the difference between the reduced viscous drag and the increased pressure drag. Subsequently, a quantity of experiments and numerical simulation studies conducted by scholars reaffirmed this theory [25; 26; 27]. Following these developments, transverse grooves have been widely used in the field of engineering. For instance, [PERSON] et al. [28] designed grooves on Mixed Flow Fans, achieving a reduction of approximately 38% in turbulent energy near the leading edge and a simultaneous reduction in noise. [PERSON] et al.