When an aircraft passes through clouds containing supercooled water droplets, the leading edge’s surface will gradually accumulate ice. Ice surface roughness is an important parameter affecting the local convective heat transfer coefficient and the water collection coefficient, which in turn affect the ice’s shape. However, because the surface roughness of aircraft icing is a transient value varying in time and space, it is extremely difficult to measure with existing methods in real time. In this study, a noncontact ultrasonic pulse-echo (UPE) technique is applied to characterize the ice roughness of an airfoil model’s surface. A multilayer model with equivalent bead-like roughness profiles is established to study the effects of changes in ice roughness on ultrasonic echo signals. A series of simulations indicated that ice roughness can be measured quantitatively and effectively in the range of [11.6, 120] μm. Based on these simulations, an experimental UPE device was developed to measure echo signals on top of the ice corresponding to surface roughness. The results show that for both the regular and irregular surface roughness samples, the maximum relative error in the roughness is less than 15%. Meanwhile, we designed and supplemented the experiment with the NACA-0012 airfoil model to realize the online measurement of ice roughness in an icing research tunnel.

Icing phenomena occur on aircraft and unmanned aerial vehicles (UAVs) under extreme weather conditions. Ultrasonic detection technology is an effective method for measuring ice formation while maintaining the shape of the structure. However, current ultrasonic sensors, which are large and inflexible, are unsuitable for irregular UAV bodies, limiting their applications in real scenarios. For the detection of icing on curved structure, this study proposes a novel flexible ultra-thin ultrasonic transducer (FUTUT). The transducer exhibits excellent flexibility, making it suitable for use on high-curvature wings. Firstly, the FUTUT was designed based on the material properties of the airframe and the sensitivity requirements for ice detection, following the design guidelines for 1-3 type piezocomposites. The fabrication process for the FUTUT was then investigated, and its flexibility and low-temperature resistance were tested. Finally, icing detection experiments were conducted in an icing wind tunnel (IWT), where the FUTUT of 9.82 MHz demonstrated an ice-thickness-detection sensitivity of 0.29 mm. Experimental results indicate that the FUTUT possesses superior flexibility and exhibits excellent stability in low-temperature environments. These results underscore the FUTUT’s promise for applications in ice detection on curved structures.