An Experimental Study on the Detrimental Effects of Rainfall on the Aerodynamic Performance of a Wind Turbine Blade Model

An experimental investigation was conducted to examine the detrimental effects of rainfall on the aerodynamic performance of wind turbine blades under various test conditions. The experimental study was performed with a typical wind turbine airfoil/blade model mounted inside a unique Icing Research Tunnel of Iowa State University (i.e., ISU-IRT). In addition to using high-sensitive load cells to measure the variations of aerodynamic forces (i.e., both life and drag forces) acting on the airfoil/blade model as a function of the incoming airflow speed and rainfall rate, a high-speed imaging system was also used to record the dynamic impingement of airborne raindrops and transient behavior of the wind-driven water runback over the surface of the test model. A high-solution digital PIV system was also used to quantify the evolution of the airflow characteristics over the surface of the airfoil/blade model induced by raindrop impingement and its correlations with rainfall-induced aerodynamic degradation under various test conditions. By applying a superhydrophobic coating to coat the surface of the airfoil/blade t model, the effects of the surface wettability of the airfoil/blade model on the rainfall-induced aerodynamic degradation were also evaluated quantitatively in comparison to those of the uncoated case.