Low Reynolds Number Investigation of the Flow Over a NACA 0012 Airfoil at Different Rainfall Rates

Abstract

The influence of different rain rates on the aerodynamic performance of the NACA 0012 airfoil with a low Reynolds number of 1×105 was investigated. Wind tunnel tests were conducted to determine lift and drag coefficients at various angles of attack in both dry and wet conditions and the results were compared to show the effects of Liquid Water Contents (LWC) at airfoil performance. Four different rainfall rates were simulated by injecting water droplets from commercial rain simulation nozzles upstream of the airfoil model, corresponding to LWCs of 20.548 g/m3, 37.745 g/m3, 41.096 g/m3 and 75.491 g/m3. A computational fluid dynamics code was utilized to gain further knowledge on the flow field. The simulation of rain was accomplished by using the two-phase flow Discrete Phase Model. It was concluded that degradation of aerodynamic performance increases with increasing LWC up to stall angle and stall is delayed for all rain rates. The computational results showed that larger droplets were more susceptible to droplet breakup than smaller droplets and generally breakup near regions with severe pressure gradients, close to the airfoil. The water film height and the location of rivulet formation on the upper surface of the airfoil are also presented.