Effects of Wind Tunnel Aerodynamic Blockage on Stagnation Collection Efficiency in an Icing Environment

摘要

A multi-phase research program in the National Research Council of Canada's Altitude Icing Wind Tunnel was completed over the course of two years investigating the effects of aerodynamic blockage on the ice accumulation at the leading edge of airfoils. This work has particular application to the testing of unmanned aerial vehicles in icing conditions; the wing sections for these vehicles are often tested at full-scale and create significant aerodynamic blockage in the test section. It has been observed that for large models, the ice accumulation at the stagnation point does not match theoretical predictions based on the empty tunnel calibration. Using NACA 0012 and NACA 4412 airfoil models, a correlation has been established that suggests aerodynamic blockage increases the stagnation point collection efficiency when the droplet Reynolds number is less than 100. The experimental test program covered a range of droplet sizes, liquid water contents and airspeeds typically observed when testing airfoils in the NRC icing wind tunnel.