Flat-Plate as a Lift Generating Device for Low Reynolds Number Applications

Abstract

Fluid flow, particularly in aerodynamics, has long been a complex area of study. Most aerodynamic research has focused on Reynolds numbers (Re) around 10⁶, relevant to commercial airliners, leading to highly optimized wing designs for that regime. However, these designs are not directly applicable at lower Re (10⁴–10⁶), typically seen in Micro Aerial Vehicles (MAVs) and micro wind turbines, where size constraints limit performance gains. Experimental studies have shown that at low Re, simply scaling down conventional wings does not replicate performance. Interestingly, flat-plates can outperform streamlined airfoils in terms of lift-to-drag ratio (L/D), often providing a more stable L/D below Re 10⁶. This is attributed to differences in flow separation and laminar separation bubble behavior, where initiating transition to turbulence can be beneficial. Wind tunnel experiments were conducted on flat-plates with various aspect ratios, incorporating inverted dimples to promote transition and improve lift. Inspired by bird wing-tip feathers, further modifications aimed to enhance lift without significantly increasing drag. With advances in technology and growing MAV applications, flat-plates show promising potential as efficient, simple lift-generating surfaces for low-Re flow.