Experimental characterization of the aerodynamics and acoustics of bio-inspired, serrated wind turbine blades

Abstract In regard to the development of more efficient and silent wind turbines, the present study consists of experimentally assessing the potential aero-acoustic benefits offered by bio-inspired, serrated blades. To this end, a conventional wind turbine blade (NREL Phase VI) is modified such that its leading edge exhibits serrations of various designs (amplitude and wavelength). The resulting serrated blades are then characterized from both an aerodynamic and an acoustic perspective, which is achieved through dual aero-acoustic tests. Involving a small-scale, fully instrumented wind turbine rig, these aero-acoustic tests are performed within both a closed-vein aerodynamic wind tunnel and an anechoic chamber, thereby allowing for measurement of the aerodynamic performance and the noise signatures entailed by the blades’ serrations, depending on their designs. From an aerodynamic standpoint, the serrated blades exhibit superior performance to their baseline counterpart, which translate into significantly higher spinning rates and power coefficients. These benefits are robust, being relatively insensitive to the inflow conditions (yaw, pitch, upstream turbulence) and, to a lesser extent, the serration design considered. From an acoustic perspective, the serrated blades exhibit more diverse noise signatures, depending on their serration design, the rotational regime and, in some cases, the radiative direction considered. Whereas no clear trend can be drawn at lower spinning rates, the higher rotational regime reveals more consistent patterns, e.g., the blades with smaller (resp. larger) serrations systematically radiate less (resp. more) noise than their baseline counterpart. All in all, these findings indicate that leading-edge serrations may offer an efficient passive flow control solution to improve the aero-acoustic characteristics of wind turbine blades. They nevertheless call for extra caution when designing serrated blades, owing to their sensitivity towards their serration design.