Aerodynamic effect of icing/rain impacts on super-hydrophobic surfaces

Abstract

The rain impact and ice accretion on different aerodynamic constructions represent a large problem to their safety and operation. Most current de-icing systems include either physical or chemical removal of ice, which is resource-and energy-intensive as well as environmentally polluting. A more desirable approach to prevent initial ice formation from water droplets on a surface is to employ highly ordered super-hydrophobic materials, which mimic lotus leaves and other natural dirt-and water-repelling surfaces and reproduced in many laboratory tests. The ability to fend off water droplets could lead to prevention of icing as an inherent material property, which further would prevent ice formations, rather than fighting its build-up. Our objective is to draw attention to problems of an extension of this effect to technical applications. The main idea of the icing or rain protection of the different aerodynamic constructions may be the use of superhydrophobic thermoplastic polymers with the water-repellent properties to prevent corrosion, improve aerodynamics or add self-cleaning properties to the material. The purpose of the present study is to explore the possibility of using a fast and cheap technology of R2R-EC to enable the fabrication of nanostructures on polymer foils of sizes ranging from 50 nanometers and up to 100 micrometers with the aim of improving the ice-cleaning and water-repellent properties of the coating. This high-speed and low-cost lithography method is developed at DTU and Danapak Flexibles A/S. These superhydrophobic surfaces with water-repelling structures provide rebound actions on the impacting droplets with the large contact angle θ. For the foils with the different micro-and nanostructures, the wetting properties are measured and impact with single droplet is presented. These coatings can be used for different engineering tasks, which need to establish and test new anti-icing/rain solutions for complex aerodynamic flows. We will start the present investigation from the initial point to include main aspects of the previous water-repellent investigations and test a single droplet impacts on the surface with the thermoplastic foil for the coating.

Toolbox for optimizing anti‐erosion protective coatings of wind turbine blades: Overview of mechanisms and technical solutions

“…Another effect of surface roughness on the droplet/surface interaction is the water-repellent effect of structured surfaces, with micropillar and nano-grass pattern, which change the contact angles (as suggested in Okulova et al 130 ). Okulova et al 130 proposed coatings with waterrepellent structures on the surface, micropillar pattern, and nano-grass.…”

“…Another effect of surface roughness on the droplet/surface interaction is the water-repellent effect of structured surfaces, with micropillar and nano-grass pattern, which change the contact angles (as suggested in Okulova et al 130 ). Okulova et al 130 proposed coatings with waterrepellent structures on the surface, micropillar pattern, and nano-grass. They also developed a technology for fabrication of nanostructures on polymer foils to produce coatings with ice-cleaning and water-repellent structures on the surface, micropillar pattern, and nano-grass (an array of nano-sized randomly distributed nano-needles), which change the contact angles.…”

Physical De-Icing Techniques for Wind Turbine Blades

“…This part of the review focuses on the essential concept of our consideration basing on water repellent surfaces inspired by natural plants and animals. Many plant leaves or animal skins contain different 3D roughness with complex geometries of nano-and microscale to reduce the flow friction, eliminating the water droplets on the coating, which were used for de-icing special effects in [24,46,47]. The surface structure of the lotus leaf was described in 1997 [48].…”

“…Figure 5a,b shows the image of the surface leaves of a lotus and a droplet contacting on the surface [47]. Figure 5c,d presents a superhydrophobic polymer surface inspired by leaves of the plants and skins of the animals, with the so-called lotus effect.…”

“…The imprinted films can be mounted on the blades or directly imprinted on the blade surface; however, a methodology for these techniques is not available in the literature. The surface properties in complex aerodynamic flows should be studied before commencing the development of this technology [47]. The established wear resistance and hydrophobic properties of the nanostructured polymer coatings have to correspond to the characteristics of applications in which friction losses and de-icing are vital.…”